THz acoustic phonon spectroscopy and nanoscopy by using piezoelectric semiconductor heterostructures.

PubMed

Mante, Pierre-Adrien; Huang, Yu-Ru; Yang, Szu-Chi; Liu, Tzu-Ming; Maznev, Alexei A; Sheu, Jinn-Kong; Sun, Chi-Kuang

2015-02-01

Thanks to ultrafast acoustics, a better understanding of acoustic dynamics on a short time scale has been obtained and new characterization methods at the nanoscale have been developed. Among the materials that were studied during the development of ultrafast acoustics, nitride based heterostructures play a particular role due to their piezoelectric properties and the possibility to generate phonons with over-THz frequency and bandwidth. Here, we review some of the work performed using this type of structure, with a focus on THz phonon spectroscopy and nanoscopy. First, we present a brief description of the theory of coherent acoustic phonon generation by piezoelectric heterostructure. Then the first experimental observation of coherent acoustic phonon generated by the absorption of ultrashort light pulses in piezoelectric heterostructures is presented. From this starting point, we then present some methods developed to realize customizable phonon generation. Finally we review some more recent applications of these structures, including imaging with a nanometer resolution, broadband attenuation measurements with a frequency up to 1THz and phononic bandgap characterization. Copyright © 2014 Elsevier B.V. All rights reserved.

Analytical Modeling of Acoustic Phonon-Limited Mobility in Strained Graphene Nanoribbons

NASA Astrophysics Data System (ADS)

Yousefvand, Ali; Ahmadi, Mohammad T.; Meshginqalam, Bahar

2017-11-01

Recent advances in graphene nanoribbon-based electronic devices encourage researchers to develop modeling and simulation methods to explore device physics. On the other hand, increasing the operating speed of nanoelectronic devices has recently attracted significant attention, and the modification of acoustic phonon interactions because of their important effect on carrier mobility can be considered as a method for carrier mobility optimization which subsequently enhances the device speed. Moreover, strain has an important influence on the electronic properties of the nanoelectronic devices. In this paper, the acoustic phonons mobility of armchair graphene nanoribbons ( n-AGNRs) under uniaxial strain is modeled analytically. In addition, strain, width and temperature effects on the acoustic phonon mobility of strained n-AGNRs are investigated. An increment in the strained AGNR acoustic phonon mobility by increasing the ribbon width is reported. Additionally, two different behaviors for the acoustic phonon mobility are verified by increasing the applied strain in 3 m, 3 m + 2 and 3 m + 1 AGNRs. Finally, the temperature effect on the modeled AGNR phonon mobility is explored, and mobility reduction by raising the temperature is reported.

Off-axis phonon and photon propagation in porous silicon superlattices studied by Brillouin spectroscopy and optical reflectance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, L. C., E-mail: lcparsons@mun.ca; Andrews, G. T., E-mail: tandrews@mun.ca

2014-07-21

Brillouin light scattering experiments and optical reflectance measurements were performed on a pair of porous silicon-based optical Bragg mirrors which had constituent layer porosity ratios close to unity. For off-axis propagation, the phononic and photonic band structures of the samples were modeled as a series of intersecting linear dispersion curves. Zone-folding was observed for the longitudinal bulk acoustic phonon and the frequency of the probed zone-folded longitudinal phonon was shown to be dependent on the propagation direction as well as the folding order of the mode branch. There was no conclusive evidence of coupling between the transverse and the foldedmore » longitudinal modes. Two additional observed Brillouin peaks were attributed to the Rayleigh surface mode and a possible pseudo-surface mode. Both of these modes were dispersive, with the velocity increasing as the wavevector decreased.« less

Topological phononic insulator with robust pseudospin-dependent transport

NASA Astrophysics Data System (ADS)

Xia, Bai-Zhan; Liu, Ting-Ting; Huang, Guo-Liang; Dai, Hong-Qing; Jiao, Jun-Rui; Zang, Xian-Guo; Yu, De-Jie; Zheng, Sheng-Jie; Liu, Jian

2017-09-01

Topological phononic states, which facilitate unique acoustic transport around defects and disorders, have significantly revolutionized our scientific cognition of acoustic systems. Here, by introducing a zone folding mechanism, we realize the topological phase transition in a double Dirac cone of the rotatable triangular phononic crystal with C3 v symmetry. We then investigate the distinct topological edge states on two types of interfaces of our phononic insulators. The first one is a zigzag interface which simultaneously possesses a symmetric mode and an antisymmetric mode. Hybridization of the two modes leads to a robust pseudospin-dependent one-way propagation. The second one is a linear interface with a symmetric mode or an antisymmetric mode. The type of mode is dependent on the topological phase transition of the phononic insulators. Based on the rotatability of triangular phononic crystals, we consider several complicated contours defined by the topological zigzag interfaces. Along these contours, the acoustic waves can unimpededly transmit without backscattering. Our research develops a route for the exploration of the topological phenomena in experiments and provides an excellent framework for freely steering the acoustic backscattering-immune propagation within topological phononic structures.

Interaction of surface plasmon polaritons and acoustic waves inside an acoustic cavity.

PubMed

Khokhlov, Nikolai; Knyazev, Grigoriy; Glavin, Boris; Shtykov, Yakov; Romanov, Oleg; Belotelov, Vladimir

2017-09-15

In this Letter, we introduce an approach for manipulation of active plasmon polaritons via acoustic waves at sub-terahertz frequency range. The acoustic structures considered are designed as phononic Fabry-Perot microresonators where mirrors are presented with an acoustic superlattice and the structure's surface, and a plasmonic grating is placed on top of the acoustic cavity so formed. It provides phonon localization in the vicinity of the plasmonic grating at frequencies within the phononic stop band enhancing phonon-light interaction. We consider phonon excitation by shining a femtosecond laser pulse on the plasmonic grating. Appropriate theoretical model was used to describe the acoustic process caused by the pump laser pulse in the GaAs/AlAs-based acoustic cavity with a gold grating on top. Strongest modulation is achieved upon excitation of propagating surface plasmon polaritons and hybridization of propagating and localized plasmons. The relative changes in the optical reflectivity of the structure are more than an order of magnitude higher than for the structure without the plasmonic film.

Polariton-acoustic-phonon interaction in a semiconductor microcavity

NASA Astrophysics Data System (ADS)

Cassabois, G.; Triques, A. L. C.; Bogani, F.; Delalande, C.; Roussignol, Ph.; Piermarocchi, C.

2000-01-01

The broadening of polariton lines by acoustic phonons is investigated in a semiconductor microcavity by means of interferometric correlation measurements with subpicosecond resolution. A decrease of the polariton-acoustic phonon coupling is clearly observed for the lower polariton branch as one approaches the resonance between exciton and photon states. This behavior cannot be explained in terms of a semiclassical linear dispersion theory but requires a full quantum description of the microcavity in the strong-coupling regime.

Subterahertz Longitudinal Phonon Modes Propagating in a Lipid Bilayer Immersed in an Aqueous Medium

NASA Astrophysics Data System (ADS)

Zakhvataev, V. E.

2018-04-01

The properties of subterahertz longitudinal acoustic phonon modes in the hydrophobic region of a lipid bilayer immersed in a compressible viscous aqueous medium are investigated theoretically. An approximate expression is obtained for the Mandelstam-Brillouin components of the dynamic structure factor of a bilayer. The analysis is based on a generalized hydrodynamic model of the "two-dimensional lipid bilayer + three-dimensional fluid medium" system, as well as on known sharp estimates for the frequencies and lifetimes of long-wavelength longitudinal acoustic phonons in a free hydrated lipid bilayer and in water, obtained from inelastic X-ray scattering experiments and molecular dynamics simulations. It is shown that, for characteristic values of the parameters of the membrane system, subterahertz longitudinal phonon-like excitations in the hydrophobic part of the bilayer are underdamped. In this case, the contribution of the viscous flow of the aqueous medium to the damping of a longitudinal membrane mode is small compared with the contribution of the lipid bilayer. Quantitative estimates of the damping ratio agree well with the experimental results for the vibration mode of the enzyme lysozyme in aqueous solution [1]. It is also shown that a coupling between longitudinal phonon modes of the bilayer and relaxation processes in its fluid environment gives rise to an additional peak in the scattering spectrum, which corresponds to a non-propagating mode.

Electron-acoustic phonon coupling in single crystal CH3NH3PbI3 perovskites revealed by coherent acoustic phonons

NASA Astrophysics Data System (ADS)

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; Yartsev, Arkady

2017-02-01

Despite the great amount of attention CH3NH3PbI3 has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH3NH3PbI3 single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm2 V-1 s-1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH3NH3PbI3.

Electron–acoustic phonon coupling in single crystal CH 3NH 3PbI 3 perovskites revealed by coherent acoustic phonons

DOE PAGES

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.; ...

2017-02-08

The intrinsic properties of CH 3NH 3PbI 3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH 3NH 3PbI 3 single crystal.We measure the acoustic phonon properties and characterizemore » electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm 2V -1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH 3NH 3PbI 3.« less

Electron–acoustic phonon coupling in single crystal CH 3NH 3PbI 3 perovskites revealed by coherent acoustic phonons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mante, Pierre-Adrien; Stoumpos, Constantinos C.; Kanatzidis, Mercouri G.

The intrinsic properties of CH 3NH 3PbI 3 are still largely unknown in spite of the great amount of attention it has received for its solar cell application. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. Furthermore, we apply this method to characterize a CH 3NH 3PbI 3 single crystal.We measure the acoustic phonon properties and characterizemore » electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. These results reveal high electron and hole mobilities of 2,800 and 9,400 cm 2V -1 s -1 , respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH 3NH 3PbI 3.« less

Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

DOE PAGES

Kargar, Fariborz; Ramirez, Sylvester; Debnath, Bishwajit; ...

2015-10-28

We report results of a combined investigation of thermal conductivity and acoustic phonon spectra in nanoporous alumina membranes with the pore diameter decreasing from D=180 nm to 25 nm. The samples with the hexagonally arranged pores were selected to have the same porosity Ø ≈13%. The Brillouin-Mandelstam spectroscopy measurements revealed bulk-like phonon spectrum in the samples with D = 180 nm pores and spectral features, which were attributed to spatial confinement, in the samples with 25 nm and 40 nm pores. The velocity of the longitudinal acoustic phonons was reduced in the samples with smaller pores. As a result, analysismore » of the experimental data and calculated phonon dispersion suggests that both phonon-boundary scattering and phonon spatial confinement affect heat conduction in membranes with the feature sizes D < 40 nm.« less

Bragg Coherent Diffractive Imaging of Zinc Oxide Acoustic Phonons at Picosecond Timescales

DOE PAGES

Ulvestad, A.; Cherukara, M. J.; Harder, R.; ...

2017-08-29

Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4Dmore » evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. Lastly, we find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.« less

Bragg Coherent Diffractive Imaging of Zinc Oxide Acoustic Phonons at Picosecond Timescales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulvestad, A.; Cherukara, M. J.; Harder, R.

Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4Dmore » evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. Lastly, we find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.« less

Coherent phonon optics in a chip with an electrically controlled active device.

PubMed

Poyser, Caroline L; Akimov, Andrey V; Campion, Richard P; Kent, Anthony J

2015-02-05

Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378 GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale.

Direct observation of confined acoustic phonon polarization branches in free-standing semiconductor nanowires

DOE PAGES

Kargar, Fariborz; Debnath, Bishwajit; Kakko, Joona -Pekko; ...

2016-11-10

Similar to electron waves, the phonon states in semiconductors can undergo changes induced by external boundaries. However, despite strong scientific and practical importance, conclusive experimental evidence of confined acoustic phonon polarization branches in individual free-standing nanostructures is lacking. Here we report results of Brillouin-Mandelstam light scattering spectroscopy, which reveal multiple (up to ten) confined acoustic phonon polarization branches in GaAs nanowires with a diameter as large as 128 nm, at a length scale that exceeds the grey phonon mean-free path in this material by almost an order-of-magnitude. The dispersion modification and energy scaling with diameter in individual nanowires are inmore » excellent agreement with theory. The phonon confinement effects result in a decrease in the phonon group velocity along the nanowire axis and changes in the phonon density of states. Furthermore, the obtained results can lead to more efficient nanoscale control of acoustic phonons, with benefits for nanoelectronic, thermoelectric and spintronic devices.« less

Extremely Low Loss Phonon-Trapping Cryogenic Acoustic Cavities for Future Physical Experiments

PubMed Central

Galliou, Serge; Goryachev, Maxim; Bourquin, Roger; Abbé, Philippe; Aubry, Jean Pierre; Tobar, Michael E.

2013-01-01

Low loss Bulk Acoustic Wave devices are considered from the point of view of the solid state approach as phonon-confining cavities. We demonstrate effective design of such acoustic cavities with phonon-trapping techniques exhibiting extremely high quality factors for trapped longitudinally-polarized phonons of various wavelengths. Quality factors of observed modes exceed 1 billion, with a maximum Q-factor of 8 billion and Q × f product of 1.6 · 1018 at liquid helium temperatures. Such high sensitivities allow analysis of intrinsic material losses in resonant phonon systems. Various mechanisms of phonon losses are discussed and estimated. PMID:23823569

Acoustic interference suppression of quartz crystal microbalance sensor arrays utilizing phononic crystals

NASA Astrophysics Data System (ADS)

Chen, Yung-Yu; Huang, Li-Chung; Wang, Wei-Shan; Lin, Yu-Ching; Wu, Tsung-Tsong; Sun, Jia-Hong; Esashi, Masayoshi

2013-04-01

Acoustic interference suppression of quartz crystal microbalance (QCM) sensor arrays utilizing phononic crystals is investigated in this paper. A square-lattice phononic crystal structure is designed to have a complete band gap covering the QCM's resonance frequency. The monolithic sensor array consisting of two QCMs separated by phononic crystals is fabricated by micromachining processes. As a result, 12 rows of phononic crystals with band gap boost insertion loss between the two QCMs by 20 dB and also reduce spurious modes. Accordingly, the phononic crystal is verified to be capable of suppressing the acoustic interference between adjacent QCMs in a sensor array.

One-electron propagation in Fermi, Pasta, Ulam disordered chains with Gaussian acoustic pulse pumping

NASA Astrophysics Data System (ADS)

Silva, L. D. Da; Dos Santos, J. L. L.; Ranciaro Neto, A.; Sales, M. O.; de Moura, F. A. B. F.

In this work, we consider a one-electron moving on a Fermi, Pasta, Ulam disordered chain under effect of electron-phonon interaction and a Gaussian acoustic pulse pumping. We describe electronic dynamics using quantum mechanics formalism and the nonlinear atomic vibrations using standard classical physics. Solving numerical equations related to coupled quantum/classical behavior of this system, we study electronic propagation properties. Our calculations suggest that the acoustic pumping associated with the electron-lattice interaction promote a sub-diffusive electronic dynamics.

Propagation of THz acoustic wave packets in GaN at room temperature

NASA Astrophysics Data System (ADS)

Maznev, A. A.; Hung, T.-C.; Yao, Y.-T.; Chou, T.-H.; Gandhi, J. S.; Lindsay, L.; Shin, H. D.; Stokes, D. W.; Forrest, R. L.; Bensaoula, A.; Sun, C.-K.; Nelson, K. A.

2018-02-01

We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1-1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as high as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.

Depth-Dependent Defect Studies Using Coherent Acoustic Phonons

DTIC Science & Technology

2014-09-29

using CAP waves as an active moving interface to induce local changes in electric, acoustic , and optical properties. This is able to generate ultrafast...the elastic strain component [6]. b) Modification of the crystal lattice due to transient strain caused by the coherent acoustic phonon wave . The...opto-electronic properties of materials. We are also using CAP waves as an active moving interface to induce local changes in electric, acoustic , and

Acoustic phonon spectrum engineering in bulk crystals via incorporation of dopant atoms

NASA Astrophysics Data System (ADS)

Kargar, Fariborz; Penilla, Elias H.; Aytan, Ece; Lewis, Jacob S.; Garay, Javier E.; Balandin, Alexander A.

2018-05-01

We report results of Brillouin—Mandelstam spectroscopy of transparent Al2O3 crystals with Nd dopants. The ionic radius and atomic mass of Nd atoms are distinctively different from those of the host Al atoms. Our results show that even a small concentration of Nd atoms incorporated into the Al2O3 samples produces a profound change in the acoustic phonon spectrum. The velocity of the transverse acoustic phonons decreases by ˜600 m/s at the Nd density of only ˜0.1%. Interestingly, the decrease in the phonon frequency and velocity with the doping concentration is non-monotonic. The obtained results, demonstrating that modification of the acoustic phonon spectrum can be achieved not only by traditional nanostructuring but also by low-concentration doping, have important implications for thermal management as well as thermoelectric and optoelectronic devices.

Defect-mediated phonon dynamics in TaS2 and WSe2

PubMed Central

Cremons, Daniel R.; Plemmons, Dayne A.; Flannigan, David J.

2017-01-01

We report correlative crystallographic and morphological studies of defect-dependent phonon dynamics in single flakes of 1T-TaS2 and 2H-WSe2 using selected-area diffraction and bright-field imaging in an ultrafast electron microscope. In both materials, we observe in-plane speed-of-sound acoustic-phonon wave trains, the dynamics of which (i.e., emergence, propagation, and interference) are strongly dependent upon discrete interfacial features (e.g., vacuum/crystal and crystal/crystal interfaces). In TaS2, we observe cross-propagating in-plane acoustic-phonon wave trains of differing frequencies that undergo coherent interference approximately 200 ps after initial emergence from distinct interfacial regions. With ultrafast bright-field imaging, the properties of the interfering wave trains are observed to correspond to the beat frequency of the individual oscillations, while intensity oscillations of Bragg spots generated from selected areas within the region of interest match well with the real-space dynamics. In WSe2, distinct acoustic-phonon dynamics are observed emanating and propagating away from structurally dissimilar morphological discontinuities (vacuum/crystal interface and crystal terrace), and results of ultrafast selected-area diffraction reveal thickness-dependent phonon frequencies. The overall observed dynamics are well-described using finite element analysis and time-dependent linear-elastic continuum mechanics. PMID:28503630

Femtosecond electron imaging of defect-modulated phonon dynamics

PubMed Central

Cremons, Daniel R.; Plemmons, Dayne A.; Flannigan, David J.

2016-01-01

Precise manipulation and control of coherent lattice oscillations via nanostructuring and phonon-wave interference has the potential to significantly impact a broad array of technologies and research areas. Resolving the dynamics of individual phonons in defect-laden materials presents an enormous challenge, however, owing to the interdependent nanoscale and ultrafast spatiotemporal scales. Here we report direct, real-space imaging of the emergence and evolution of acoustic phonons at individual defects in crystalline WSe2 and Ge. Via bright-field imaging with an ultrafast electron microscope, we are able to image the sub-picosecond nucleation and the launch of wavefronts at step edges and resolve dispersion behaviours during propagation and scattering. We discover that the appearance of speed-of-sound (for example, 6 nm ps−1) wavefronts are influenced by spatially varying nanoscale strain fields, taking on the appearance of static bend contours during propagation. These observations provide unprecedented insight into the roles played by individual atomic and nanoscale features on acoustic-phonon dynamics. PMID:27079790

Acoustically-driven surface and hyperbolic plasmon-phonon polaritons in graphene/h-BN heterostructures on piezoelectric substrates

NASA Astrophysics Data System (ADS)

Fandan, R.; Pedrós, J.; Schiefele, J.; Boscá, A.; Martínez, J.; Calle, F.

2018-05-01

Surface plasmon polaritons in graphene couple strongly to surface phonons in polar substrates leading to hybridized surface plasmon-phonon polaritons (SPPPs). We demonstrate that a surface acoustic wave (SAW) can be used to launch propagating SPPPs in graphene/h-BN heterostructures on a piezoelectric substrate like AlN, where the SAW-induced surface modulation acts as a dynamic diffraction grating. The efficiency of the light coupling is greatly enhanced by the introduction of the h-BN film as compared to the bare graphene/AlN system. The h-BN interlayer not only significantly changes the dispersion of the SPPPs but also enhances their lifetime. The strengthening of the SPPPs is shown to be related to both the higher carrier mobility induced in graphene and the coupling with h-BN and AlN surface phonons. In addition to surface phonons, hyperbolic phonons polaritons (HPPs) appear in the case of multilayer h-BN films leading to hybridized hyperbolic plasmon-phonon polaritons (HPPPs) that are also mediated by the SAW. These results pave the way for engineering SAW-based graphene/h-BN plasmonic devices and metamaterials covering the mid-IR to THz range.

Photoinduced coherent acoustic phonon dynamics inside Mott insulator Sr2IrO4 films observed by femtosecond X-ray pulses

NASA Astrophysics Data System (ADS)

Zhang, Bing-Bing; Liu, Jian; Wei, Xu; Sun, Da-Rui; Jia, Quan-Jie; Li, Yuelin; Tao, Ye

2017-04-01

We investigate the transient photoexcited lattice dynamics in a layered perovskite Mott insulator Sr2IrO4 film by femtosecond X-ray diffraction using a laser plasma-based X-ray source. The ultrafast structural dynamics of Sr2IrO4 thin films are determined by observing the shift and broadening of (0012) Bragg diffraction after excitation by 1.5 eV and 3.0 eV pump photons for films with different thicknesses. The observed transient lattice response can be well interpreted as a distinct three-step dynamics due to the propagation of coherent acoustic phonons generated by photoinduced quasiparticles (QPs). Employing a normalized phonon propagation model, we found that the photoinduced angular shifts of the Bragg peak collapse into a universal curve after introducing normalized coordinates to account for different thicknesses and pump photon energies, pinpointing the origin of the lattice distortion and its early evolution. In addition, a transient photocurrent measurement indicates that the photoinduced QPs are charge neutral excitons. Mapping the phonon propagation and correlating its dynamics with the QP by ultrafast X-ray diffraction (UXRD) establish a powerful way to study electron-phonon coupling and uncover the exotic physics in strongly correlated systems under nonequilibrium conditions.

Canada Basin Acoustic Propagation Experiment (CANAPE)

DTIC Science & Technology

2015-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Canada Basin Acoustic Propagation Experiment (CANAPE...ocean structure. Changes in sea ice and the water column affect both acoustic propagation and ambient noise. This implies that what was learned...about Arctic acoustics during the Cold War is now obsolete. The goal of the Canada Basin Acoustic Propagation Experiment (CANAPE) is to determine the

Imaginary parts of coupled electron and phonon propagators

NASA Astrophysics Data System (ADS)

Schwartzman, K.; Lawrence, W. E.

1988-01-01

Quasiparticle and phonon damping rates due to the electron-phonon and Coulomb interactions are obtained directly from the self-energy formalism of strong-coupling theory. This accounts for all processes involving phonon or quasiparticle decay into a single particle-hole pair, or quasiparticle decay by emission or absorption of a single real phonon. The two quasiparticle decay modes are treated on a common footing, without ad hoc separation, by accounting fully for the dynamics of the phonon propagator and the Coulomb vertex-the latter by expansion of the four-point Coulomb vertex function. The results are shown to be expressible in terms of only the physical (i.e., fully renormalized) energies and coupling constants, and are written in terms of spectral functions such as α2F(ω) and its generalizations. Expansion of these in powers of a phonon linewidth parameter distinguishes (in lowest orders) between quasiparticle decay modes involving real and virtual phonons. However, the simplest prescription for calculating decay rates involves an effective scattering amplitude in which this distinction is not made.

Propagation of THz acoustic wave packets in GaN at room temperature

DOE PAGES

Maznev, A. A.; Hung, T.-C.; Yao, Y.-T.; ...

2018-02-05

We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1–1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as highmore » as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.« less

Propagation of THz acoustic wave packets in GaN at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maznev, A. A.; Hung, T.-C.; Yao, Y.-T.

We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1–1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as highmore » as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.« less

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites

PubMed Central

Yang, Jianfeng; Wen, Xiaoming; Xia, Hongze; Sheng, Rui; Ma, Qingshan; Kim, Jincheol; Tapping, Patrick; Harada, Takaaki; Kee, Tak W.; Huang, Fuzhi; Cheng, Yi-Bing; Green, Martin; Ho-Baillie, Anita; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Conibeer, Gavin

2017-01-01

The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I−/Br−) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials. PMID:28106061

Turbofan Acoustic Propagation and Radiation

NASA Technical Reports Server (NTRS)

Eversman, Walter

2000-01-01

This document describes progress in the development of finite element codes for the prediction of near and far field acoustic radiation from the inlet and aft fan ducts of turbofan engines. The report consists of nine papers which have appeared in archival journals and conference proceedings, or are presently in review for publication. Topics included are: 1. Aft Fan Duct Acoustic Radiation; 2. Mapped Infinite Wave Envelope Elements for Acoustic Radiation in a Uniformly Moving Medium; 3. A Reflection Free Boundary Condition for Propagation in Uniform Flow Using Mapped Infinite Wave Envelope Elements; 4. A Numerical Comparison Between Multiple-Scales and FEM Solution for Sound Propagation in Lined Flow Ducts; 5. Acoustic Propagation at High Frequencies in Ducts; 6. The Boundary Condition at an Impedance Wall in a Nonuniform Duct with Potential Flow; 7. A Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows; 8. Reciprocity and Acoustics Power in One Dimensional Compressible Potential Flows; and 9. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows.

Specularity of longitudinal acoustic phonons at rough surfaces

NASA Astrophysics Data System (ADS)

Gelda, Dhruv; Ghossoub, Marc G.; Valavala, Krishna; Ma, Jun; Rajagopal, Manjunath C.; Sinha, Sanjiv

2018-01-01

The specularity of phonons at crystal surfaces is of direct importance to thermal transport in nanostructures and to dissipation in nanomechanical resonators. Wave scattering theory provides a framework for estimating wavelength-dependent specularity, but experimental validation remains elusive. Widely available thermal conductivity data presents poor validation since the involvement of the infinitude of phonon wavelengths in thermal transport presents an underconstrained test for specularity theory. Here, we report phonon specularity by measuring the lifetimes of individual coherent longitudinal acoustic phonon modes excited in ultrathin (36-205 nm) suspended silicon membranes at room temperature over the frequency range ˜20 -118 GHz. Phonon surface scattering dominates intrinsic Akhiezer damping at frequencies ≳60 GHz, enabling measurements of phonon boundary scattering time over wavelengths ˜72 -140 nm . We obtain detailed statistics of the surface roughness at the top and bottom surfaces of membranes using HRTEM imaging. We find that the specularity of the excited modes are in good agreement with solutions of wave scattering only when the TEM statistics are corrected for projection errors. The often-cited Ziman formula for phonon specularity also appears in good agreement with the data, contradicting previous results. This work helps to advance the fundamental understanding of phonon scattering at the surfaces of nanostructures.

Elastic Wave Propagation Mechanisms in Underwater Acoustic Environments

DTIC Science & Technology

2015-09-30

Elastic wave propagation mechanisms in underwater acoustic environments Scott D. Frank Marist College Department of Mathematics Poughkeepsie...conversion from elastic propagation to acoustic propagation, and intense interface waves on underwater acoustic environments with elastic bottoms...acoustic propagation will be considered as a means to predict the presence of elastic ice layers. APPROACH In a cylindrically symmetric environment

Enhancement of coherent acoustic phonons in InGaN multiple quantum wells

NASA Astrophysics Data System (ADS)

Hafiz, Shopan D.; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit

2015-03-01

Enhancement of coherent zone folded longitudinal acoustic phonon (ZFLAP) oscillations at terahertz frequencies was demonstrated in InGaN multiple quantum wells (MQWs) by using wavelength degenerate time resolved differential transmission spectroscopy. Screening of the piezoelectric field in InGaN MQWs by photogenerated carriers upon femtosecond pulse excitation gave rise to terahertz ZFLAPs, which were monitored at the Brillouin zone center in the transmission geometry. MQWs composed of 10 pairs InxGa1-xN wells and In0.03Ga0.97N barriers provided coherent phonon frequencies of 0.69-0.80 THz depending on the period of MQWs. Dependences of ZFLAP amplitude on excitation density and wavelength were also investigated. Possibility of achieving phonon cavity, incorporating a MQW placed between two AlN/GaN phonon mirrors designed to exhibit large acoustic gaps at the zone center, was also explored.

Sub-Poissonian phonon statistics in an acoustical resonator coupled to a pumped two-level emitter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ceban, V., E-mail: victor.ceban@phys.asm.md; Macovei, M. A., E-mail: macovei@phys.asm.md

2015-11-15

The concept of an acoustical analog of the optical laser has been developed recently in both theoretical and experimental works. We here discuss a model of a coherent phonon generator with a direct signature of the quantum properties of sound vibrations. The considered setup is made of a laser-driven quantum dot embedded in an acoustical nanocavity. The system dynamics is solved for a single phonon mode in the steady-state and in the strong quantum dot—phonon coupling regime beyond the secular approximation. We demonstrate that the phonon statistics exhibits quantum features, i.e., is sub-Poissonian.

Vehicular sources in acoustic propagation experiments

NASA Technical Reports Server (NTRS)

Prado, Gervasio; Fitzgerald, James; Arruda, Anthony; Parides, George

1990-01-01

One of the most important uses of acoustic propagation models lies in the area of detection and tracking of vehicles. Propagation models are used to compute transmission losses in performance prediction models and to analyze the results of past experiments. Vehicles can also provide the means for cost effective experiments to measure acoustic propagation conditions over significant ranges. In order to properly correlate the information provided by the experimental data and the propagation models, the following issues must be taken into consideration: the phenomenology of the vehicle noise sources must be understood and characterized; the vehicle's location or 'ground truth' must be accurately reproduced and synchronized with the acoustic data; and sufficient meteorological data must be collected to support the requirements of the propagation models. The experimental procedures and instrumentation needed to carry out propagation experiments are discussed. Illustrative results are presented for two cases. First, a helicopter was used to measure propagation losses at a range of 1 to 10 Km. Second, a heavy diesel-powered vehicle was used to measure propagation losses in the 300 to 2200 m range.

Vehicular sources in acoustic propagation experiments

NASA Astrophysics Data System (ADS)

Prado, Gervasio; Fitzgerald, James; Arruda, Anthony; Parides, George

1990-12-01

One of the most important uses of acoustic propagation models lies in the area of detection and tracking of vehicles. Propagation models are used to compute transmission losses in performance prediction models and to analyze the results of past experiments. Vehicles can also provide the means for cost effective experiments to measure acoustic propagation conditions over significant ranges. In order to properly correlate the information provided by the experimental data and the propagation models, the following issues must be taken into consideration: the phenomenology of the vehicle noise sources must be understood and characterized; the vehicle's location or 'ground truth' must be accurately reproduced and synchronized with the acoustic data; and sufficient meteorological data must be collected to support the requirements of the propagation models. The experimental procedures and instrumentation needed to carry out propagation experiments are discussed. Illustrative results are presented for two cases. First, a helicopter was used to measure propagation losses at a range of 1 to 10 Km. Second, a heavy diesel-powered vehicle was used to measure propagation losses in the 300 to 2200 m range.

Picosecond acoustic phonon dynamics in LaF3:Pr3+

NASA Astrophysics Data System (ADS)

Kirkpatrick, Sean M.; Yang, Ho-Soon; Dennis, W. M.

1998-09-01

A plasma switching technique is used to generate subnanosecond, far-infrared (FIR) pulses with frequency 113 cm-1. The generation of subnanosecond FIR pulses enables us to improve the time resolution of phonon spectroscopic measurements from 50 ns to 350 ps. As an application of this technique, we investigate the subnanosecond dynamics of high-frequency phonons in 0.5% LaF3:Pr3+. In particular, we report on the generation and detection of a subnanosecond nonequilibrium phonon population at 113 cm-1, and the temporal evolution of the resulting decay products. The frequency dependence of the phonon relaxation rates of acoustic phonons in this material is found to deviate from the ω5 frequency dependence predicted by an isotropic model with linear dispersion. A more realistic model based on the actual dispersion curves of the material is presented and compared with the data.

Broadband anomalous reflection caused by unsymmetrical specific acoustic impedance in phononic crystals

NASA Astrophysics Data System (ADS)

Han, S. K.; Wu, C. W.; Chen, Z.

2018-01-01

We investigate through numerical simulation the anomalous reflection (AR) of acoustic waves with perfect phononic crystals (PCs). Broadband AR is observed in a wide angle for the oblique incidence. The AR is due to the unsymmetrical specific acoustic impedance (SAI) profile along the surface, which is caused by the high frequency incidence. The findings in this paper complement the theories for the AR of acoustic waves with PCs, and may find applications in acoustic engineerings.

Interfacing planar superconducting qubits with high overtone bulk acoustic phonons

NASA Astrophysics Data System (ADS)

Kervinen, Mikael; Rissanen, Ilkka; Sillanpää, Mika

2018-05-01

Mechanical resonators are a promising way for interfacing qubits in order to realize hybrid quantum systems that offer great possibilities for applications. Mechanical systems can have very long energy lifetimes, and they can be further interfaced to other systems. Moreover, integration of a mechanical oscillator with qubits creates a potential platform for the exploration of quantum physics in macroscopic mechanical degrees of freedom. The utilization of high overtone bulk acoustic resonators coupled to superconducting qubits is an intriguing platform towards these goals. These resonators exhibit a combination of high-frequency and high-quality factors. They can reach their quantum ground state at dilution refrigeration temperatures and they can be strongly coupled to superconducting qubits via their piezoelectric effect. In this paper, we demonstrate our system where bulk acoustic phonons of a high overtone resonator are coupled to a transmon qubit in a planar circuit architecture. We show that the bulk acoustic phonons are interacting with the qubit in a simple design architecture at the quantum level, representing further progress towards the quantum control of mechanical motion.

Application of magnetoelastic materials in spatiotemporally modulated phononic crystals for nonreciprocal wave propagation

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Attarzadeh, M. A.; Nouh, M.; Karami, M. Amin

2018-01-01

In this paper, a physical platform is proposed to change the properties of phononic crystals in space and time in order to achieve nonreciprocal wave transmission. The utilization of magnetoelastic materials in elastic phononic systems is studied. Material properties of magnetoelastic materials change significantly with an external magnetic field. This property is used to design systems with a desired wave propagation pattern. The properties of the magnetoelastic medium are changed in a traveling wave pattern, which changes in both space and time. A phononic crystal with such a modulation exhibits one-way wave propagation behavior. An extended transfer matrix method (TMM) is developed to model a system with time varying properties. The stop band and the pass band of a reciprocal and a nonreciprocal bar are found using this method. The TMM is used to find the transfer function of a magnetoelastic bar. The obtained results match those obtained via the theoretical Floquet-Bloch approach and numerical simulations. It is shown that the stop band in the transfer function of a system with temporal varying property for the forward wave propagation is different from the same in the backward wave propagation. The proposed configuration enables the physical realization of a class of smart structures that incorporates nonreciprocal wave propagation.

The influence of charge and magnetic order on polaron and acoustic phonon dynamics in LuFe 2O 4

DOE PAGES

Lee, J.; Trugman, S. A.; Zhang, C. L.; ...

2015-07-27

Femtosecond optical pump-probe spectroscopy is used to reveal the influence of charge and magnetic order on polarondynamics and coherent acoustic phonon oscillations in single crystals of charge-ordered, ferrimagnetic LuFe 2O 4. We experimentally observed the influence of magnetic order on polarondynamics. We also observed a correlation between charge order and the amplitude of the acoustic phonon oscillations, due to photoinduced changes in the lattice constant that originate from the photoexcited electrons. As a result, this provides insight into the general behavior of coherent acoustic phonon oscillations in charge-ordered materials.

Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubakaddi, S. S., E-mail: sskubakaddi@gmail.com

2016-05-21

Cerenkov acoustic phonon emission is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) when it is driven by a dc electric field E. Numerical calculations are made for Cd{sub 3}As{sub 2} in which mobility and electron concentration are large. We find that Cerenkov emission of acoustic phonons takes place when the electron drift velocity v{sub d} is greater than the sound velocity v{sub s}. This occurs at small E (∼few V/cm) due to large mobility. Frequency (ω{sub q}) and angular (θ) distribution of phonon emission spectrum P(ω{sub q}, θ) are studied for different electron drift velocities v{sub d} (i.e., differentmore » E) and electron concentrations n{sub e}. The frequency dependence of P(ω{sub q}, θ) shows a maximum P{sub m}(ω{sub q}, θ) at about ω{sub m} ≈ 1 THz and is found to increase with the increasing v{sub d} and n{sub e}. The value of ω{sub m} shifts to higher region for larger n{sub e}. It is found that ω{sub m}/n{sub e}{sup 1/3} and P{sub m}(ω{sub q}, θ)/n{sub e}{sup 2/3} are nearly constants. The latter is in contrast with the P{sub m}(ω{sub q}, θ)n{sub e}{sup 1/2 }= constant in conventional bulk semiconductor. Each maximum is followed by a vanishing spectrum at nearly “2k{sub f} cutoff,” where k{sub f} is the Fermi wave vector. Angular dependence of P(ω{sub q}, θ) and the intensity P(θ) of the phonon emission shows a maximum at an emission angle 45° and is found to increase with increasing v{sub d}. P(θ) is found to increase linearly with n{sub e} giving the ratio P(θ)/(n{sub e}v{sub d}) nearly a constant. We suggest that it is possible to have the controlled Cerenkov emission and generation of acoustic phonons with the proper choice of E, θ, and n{sub e}. 3DDS with large n{sub e} and mobility can be a good source of acoustic phonon generation in ∼THz regime.« less

Weyl points and Fermi arcs in a chiral phononic crystal

NASA Astrophysics Data System (ADS)

Li, Feng; Huang, Xueqin; Lu, Jiuyang; Ma, Jiahong; Liu, Zhengyou

2018-01-01

Topological semimetals are materials whose band structure contains touching points that are topologically nontrivial and can host quasiparticle excitations that behave as Dirac or Weyl fermions. These so-called Weyl points not only exist in electronic systems, but can also be found in artificial periodic structures with classical waves, such as electromagnetic waves in photonic crystals and acoustic waves in phononic crystals. Due to the lack of spin and a difficulty in breaking time-reversal symmetry for sound, however, topological acoustic materials cannot be achieved in the same way as electronic or optical systems. And despite many theoretical predictions, experimentally realizing Weyl points in phononic crystals remains challenging. Here, we experimentally realize Weyl points in a chiral phononic crystal system, and demonstrate surface states associated with the Weyl points that are topological in nature, and can host modes that propagate only in one direction. As with their photonic counterparts, chiral phononic crystals bring topological physics to the macroscopic scale.

Controlling competing orders via nonequilibrium acoustic phonons: Emergence of anisotropic effective electronic temperature

NASA Astrophysics Data System (ADS)

Schütt, Michael; Orth, Peter P.; Levchenko, Alex; Fernandes, Rafael M.

2018-01-01

Ultrafast perturbations offer a unique tool to manipulate correlated systems due to their ability to promote transient behaviors with no equilibrium counterpart. A widely employed strategy is the excitation of coherent optical phonons, as they can cause significant changes in the electronic structure and interactions on short time scales. One of the issues, however, is the inevitable heating that accompanies these resonant excitations. Here, we explore a promising alternative route: the nonequilibrium excitation of acoustic phonons, which, due to their low excitation energies, generally lead to less heating. We demonstrate that driving acoustic phonons leads to the remarkable phenomenon of a momentum-dependent effective temperature, by which electronic states at different regions of the Fermi surface are subject to distinct local temperatures. Such an anisotropic effective electronic temperature can have a profound effect on the delicate balance between competing ordered states in unconventional superconductors, opening a so far unexplored avenue to control correlated phases.

Topological phononic states of underwater sound based on coupled ring resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Cheng; Li, Zheng; Ni, Xu

We report a design of topological phononic states for underwater sound using arrays of acoustic coupled ring resonators. In each individual ring resonator, two degenerate acoustic modes, corresponding to clockwise and counter-clockwise propagation, are treated as opposite pseudospins. The gapless edge states arise in the bandgap resulting in protected pseudospin-dependent sound transportation, which is a phononic analogue of the quantum spin Hall effect. We also investigate the robustness of the topological sound state, suggesting that the observed pseudospin-dependent sound transportation remains unless the introduced defects facilitate coupling between the clockwise and counter-clockwise modes (in other words, the original mode degeneracymore » is broken). The topological engineering of sound transportation will certainly promise unique design for next generation of acoustic devices in sound guiding and switching, especially for underwater acoustic devices.« less

Shear-horizontal surface acoustic wave phononic device with high density filling material for ultra-low power sensing applications

NASA Astrophysics Data System (ADS)

Richardson, M.; Sankaranarayanan, S. K. R. S.; Bhethanabotla, V. R.

2014-06-01

Finite element simulations of a phononic shear-horizontal surface acoustic wave (SAW) sensor based on ST 90°-X Quartz reveal a dramatic reduction in power consumption. The phononic sensor is realized by artificially structuring the delay path to form an acoustic meta-material comprised of a periodic microcavity array incorporating high-density materials such as tantalum or tungsten. Constructive interference of the scattered and secondary reflected waves at every microcavity interface leads to acoustic energy confinement in the high-density regions translating into reduced power loss. Tantalum filled cavities show the best performance while tungsten inclusions create a phononic bandgap. Based on our simulation results, SAW devices with tantalum filled microcavities were fabricated and shown to significantly decrease insertion loss. Our findings offer encouraging prospects for designing low power, highly sensitive portable biosensors.

Waveform-preserved unidirectional acoustic transmission based on impedance-matched acoustic metasurface and phononic crystal

NASA Astrophysics Data System (ADS)

Song, Ai-Ling; Chen, Tian-Ning; Wang, Xiao-Peng; Wan, Le-Le

2016-08-01

The waveform distortion happens in most of the unidirectional acoustic transmission (UAT) devices proposed before. In this paper, a novel type of waveform-preserved UAT device composed of an impedance-matched acoustic metasurface (AMS) and a phononic crystal (PC) structure is proposed and numerically investigated. The acoustic pressure field distributions and transmittance are calculated by using the finite element method. The subwavelength AMS that can modulate the wavefront of the transmitted wave at will is designed and the band structure of the PC structure is calculated and analyzed. The sound pressure field distributions demonstrate that the unidirectional acoustic transmission can be realized by the proposed UAT device without changing the waveforms of the output waves, which is the distinctive feature compared with the previous UAT devices. The physical mechanism of the unidirectional acoustic transmission is discussed by analyzing the refraction angle changes and partial band gap map. The calculated transmission spectra show that the UAT device is valid within a relatively broad frequency range. The simulation results agree well with the theoretical predictions. The proposed UAT device provides a good reference for designing waveform-preserved UAT devices and has potential applications in many fields, such as medical ultrasound, acoustic rectifiers, and noise insulation.

Nanoscale Phonon Transport as Probed with a Microfabricated Phonon Spectrometer for the Study of Nanoscale Energy Transport

NASA Astrophysics Data System (ADS)

Robinson, Richard; Otelaja, Obafemi; Hertzberg, Jared; Aksit, Mahmut; Stewart, Derek

2013-03-01

Phonons are the dominant heat carriers in dielectrics and a clear understanding of their behavior at the nanoscale is important for the development of efficient thermoelectric devices. In this work we show how acoustic phonon transport can be directly probed by the generation and detection of non-equilibrium phonons in microscale and nanoscale structures. Our technique employs a scalable method of fabricating phonon generators and detectors by forming Al-AlxOy-Al superconducting tunnel junctions on the sidewalls of a silicon mesa etched with KOH and an operating temperature of 0.3K. In the line-of-sight path along the width of these mesas, phonons with frequency ~100 GHz can propagate ballistically The phonons radiate into the mesa and are observed by the detector after passing through the mesa. We fabricated silicon nanosheets of width 100 to 300 nm along the ballistic path and observe surface scattering effects on phonon transmission when the characteristic length scale of a material is less than the phonon mean free path. We compare our results to the Casimir-Ziman theory. Our methods can be adapted for studying phonon transport in other nanostructures and will improve the understanding of phonon contribution to thermal transport. The work was supported in part by the National Science Foundation under Agreement No. DMR-1149036.

Pressure dependence of transverse acoustic phonon energy in ferropericlase across the spin transition.

PubMed

Fukui, Hiroshi; Baron, Alfred Q R; Ishikawa, Daisuke; Uchiyama, Hiroshi; Ohishi, Yasuo; Tsuchiya, Taku; Kobayashi, Hisao; Matsuzaki, Takuya; Yoshino, Takashi; Katsura, Tomoo

2017-06-21

We investigated transverse acoustic (TA) phonons in iron-bearing magnesium oxide (ferropericlase) up to 56 GPa using inelastic x-ray scattering (IXS). The results show that the energy of the TA phonon far from the Brillouin zone center suddenly increases with increasing pressure above the spin transition pressure of ferropericlase. Ab initio calculations revealed that the TA phonon energy far from the Brillouin zone center is higher in the low-spin state than in the high spin state; that the TA phonon energy depend weakly on pressure; and that the energy gap between the TA and the lowest-energy-optic phonons is much narrower in the low-spin state than in the high-spin state. This allows us to conclude that the anomalous behavior of the TA mode in the present experiments is the result of gap narrowing due to the spin transition and explains contradictory results in previous experimental studies.

Dimensional analysis of acoustically propagated signals

NASA Technical Reports Server (NTRS)

Hansen, Scott D.; Thomson, Dennis W.

1993-01-01

Traditionally, long term measurements of atmospherically propagated sound signals have consisted of time series of multiminute averages. Only recently have continuous measurements with temporal resolution corresponding to turbulent time scales been available. With modern digital data acquisition systems we now have the capability to simultaneously record both acoustical and meteorological parameters with sufficient temporal resolution to allow us to examine in detail relationships between fluctuating sound and the meteorological variables, particularly wind and temperature, which locally determine the acoustic refractive index. The atmospheric acoustic propagation medium can be treated as a nonlinear dynamical system, a kind of signal processor whose innards depend on thermodynamic and turbulent processes in the atmosphere. The atmosphere is an inherently nonlinear dynamical system. In fact one simple model of atmospheric convection, the Lorenz system, may well be the most widely studied of all dynamical systems. In this paper we report some results of our having applied methods used to characterize nonlinear dynamical systems to study the characteristics of acoustical signals propagated through the atmosphere. For example, we investigate whether or not it is possible to parameterize signal fluctuations in terms of fractal dimensions. For time series one such parameter is the limit capacity dimension. Nicolis and Nicolis were among the first to use the kind of methods we have to study the properties of low dimension global attractors.

Piezoelectric substrate effect on electron-acoustic phonon scattering in bilayer graphene

NASA Astrophysics Data System (ADS)

Ansari, Mohd Meenhaz; Ashraf, SSZ

2018-05-01

We have studied the effect of piezoelectric scattering as a function of electron temperature and distance between the sample and the substrate on electron-acoustic phonon scattering rate in Bilayer Graphene sitting on a piezoelectric substrate. We obtain approximate analytical result by neglecting the chiral nature of carriers and then proceed to obtain unapproximated numerical results for the scattering rate incorporating chirality of charge carriers. We find that on the incorporation of full numerical computation the magnitude as well as the power exponent both is affected with the power exponent changed from T3 to T3.31 in the low temperature range and to T6.98 dependence in the temperature range (>5K). We also find that the distance between the sample and substrate begins to strongly affect the scattering rate at temperatures above 10K. These calculation not only suggest the influencing effect of piezoelectric substrate on the transport properties of Dirac Fermions at very low temperatures but also open a channel to study low dimension structures by probing piezoelectric acoustical phonons.

Range-Dependent Acoustic Propagation in Shallow Water with Elastic Bottom Effects

DTIC Science & Technology

2015-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Range-Dependent Acoustic Propagation in Shallow Water ...theory is inadequate for properly describing loss in shallow water acoustic propagation. Finally there is range dependence, which can be significant in...work will lead to a practical method to investigate seismo- acoustic propagation in shallow - water environments, and allow us to compare and contrast

Research on soundproof properties of cylindrical shells of generalized phononic crystals

NASA Astrophysics Data System (ADS)

Liu, Ru; Shu, Haisheng; Wang, Xingguo

2017-04-01

Based on the previous studies, the concept of generalized phononic crystals (GPCs) is further introduced into the cylindrical shell structures in this paper. And a type of cylindrical shells of generalized phononic crystals (CS-GPCs) is constructed, the structural field and acoustic-structural coupled field of the composite cylindrical shells are examined respectively. For the structural field, the transfer matrix method of mechanical state vector is adopted to build the transfer matrix of radial waves propagating from inside to outside. For the acoustic-structural coupled field, the expressions of the acoustic transmission/reflection coefficients and the sound insulation of acoustic waves with the excitation of center line sound source are set up. And the acoustic transmission coefficient and the frequency response of sound insulation in this mode were numerical calculated. Furthermore, the theoretical analysis results are verified by using the method of combining the numerical calculation and finite element simulation. Finally, the effects of inner and outer fluid parameters on the transmission/reflection coefficients of CS-GPCs are analyzed in detail.

Electron-phonon interactions in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Yu, Segi

In this dissertation, electron-phonon interactions are studied theoretically in semiconductor nanoscale heterostructures. Interactions of electrons with interface optical phonons dominate over other electron-phonon interactions in narrow width heterostructures. Hence, a transfer matrix method is used to establish a formalism for determining the dispersion relations and electrostatic potentials of the interface phonons for multiple-interface heterostructure within the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is difficult to implement. Several specific cases are treated to illustrate advantages of the formalism. Electrophonon resonance (EPR) is studied in cylindrical quantum wires using the confined/interface optical phonons representation and bulk phonon representation. It has been found that interface phonon contribution to EPR is small compared with confined phonon. Different selection rules for bulk phonons and confined phonons result in different EPR behaviors as the radius of cylindrical wire changes. Experiment is suggested to test which phonon representation is appropriate for EPR. The effects of phonon confinement on elect ron-acoustic-phonon scattering is studied in cylindrical and rectangular quantum wires. In the macroscopic elastic continuum model, the confined-phonon dispersion relations are obtained for several crystallographic directions with free-surface and clamped-surface boundary conditions in cylindrical wires. The scattering rates due to the deformation potential are obtained for these confined phonons and are compared with those of bulk-like phonons. The results show that the inclusion of acoustic phonon confinement may be crucial for calculating accurate low-energy electron scattering rates. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates. The Hamiltonian describing the

Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters.

PubMed

Werschler, Florian; Hinz, Christopher; Froning, Florian; Gumbsheimer, Pascal; Haase, Johannes; Negele, Carla; de Roo, Tjaard; Mecking, Stefan; Leitenstorfer, Alfred; Seletskiy, Denis V

2016-09-14

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic luminescence. In isolated colloidal quantum dots, spatial confinement of the vibrational motion is expected to give rise to an interplay between the quantized electronic and phononic degrees of freedom. In most cases, however, zero-dimensional colloidal nanocrystals are strongly coupled to the substrate such that the charge relaxation processes are still effectively governed by the bulk properties. Here we show that encapsulation of single colloidal CdSe/CdS nanocrystals into individual organic polymer shells allows for systematic vibrational decoupling of the semiconductor nanospheres from the surroundings. In contrast to epitaxially grown quantum dots, simultaneous quantization of both electronic and vibrational degrees of freedom results in a series of strong and narrow acoustic phonon sidebands observed in the photoluminescence. Furthermore, an individual analysis of more than 200 compound particles reveals that enhancement or suppression of the radiative properties of the fundamental exciton is controlled by the interaction between fine-structure states via the discrete vibrational modes. For the first time, pronounced resonances in the scattering rate between the fine-structure states are directly observed, in good agreement with a quantum mechanical model. The unambiguous assignment of mediating acoustic modes to the observed scattering resonances complements the experimental findings. Thus, our results form an attractive basis for future studies on subterahertz quantum opto-mechanics and efficient laser cooling at the nanoscale.

Linear and nonlinear acoustic wave propagation in the atmosphere

NASA Technical Reports Server (NTRS)

Hariharan, S. I.; Yu, Ping

1988-01-01

The investigation of the acoustic wave propagation theory and numerical implementation for the situation of an isothermal atmosphere is described. A one-dimensional model to validate an asymptotic theory and a 3-D situation to relate to a realistic situation are considered. In addition, nonlinear wave propagation and the numerical treatment are included. It is known that the gravitational effects play a crucial role in the low frequency acoustic wave propagation. They propagate large distances and, as such, the numerical treatment of those problems become difficult in terms of posing boundary conditions which are valid for all frequencies.

Cavity-type hypersonic phononic crystals

NASA Astrophysics Data System (ADS)

Sato, A.; Pennec, Y.; Yanagishita, T.; Masuda, H.; Knoll, W.; Djafari-Rouhani, B.; Fytas, G.

2012-11-01

We report on the engineering of the phonon dispersion diagram in monodomain anodic porous alumina (APA) films through the porosity and physical state of the material residing in the nanopores. Lattice symmetry and inclusion materials are theoretically identified to be the main factors which control the hypersonic acoustic wave propagation. This involves the interaction between the longitudinal and the transverse modes in the effective medium and a flat band characteristic of the material residing in the cavities. Air and filled nanopores, therefore, display markedly different dispersion relations and the inclusion materials lead to a locally resonant structural behavior uniquely determining their properties under confinement. APA films emerge as a new platform to investigate the rich acoustic phenomena of structured composite matter.

Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates.

PubMed

Tian, Zhenhua; Yu, Lingyu

2017-01-05

The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region near the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Moreover, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.

Phonon dynamics in type-VIII silicon clathrates: Beyond the rattler concept

NASA Astrophysics Data System (ADS)

Norouzzadeh, Payam; Myles, Charles W.; Vashaee, Daryoosh

2017-05-01

Clathrates can form a type of guest-host solid structures that, unlike most crystalline solids, have very low thermal conductivity. It is generally thought that the guest atoms caged inside the host framework act as "rattlers" and induce lattice dynamics disorders responsible for the small thermal conductivity. We performed a systematic study of the lattice dynamical properties of type-VIII clathrates with alkali and alkaline-earth guests, i.e., X8S i46 (X =Na , K, Rb, Cs, Ca, Sr, and Ba). The energy dependent participation ratio (PR) and the atomic participation ratio of phonon modes extracted from density functional theory calculations revealed that the rattler concept is not adequate to describe the effect of fillers as they manifest strong hybridization with the framework. For the case of heavy fillers, such as Rb, Sr, Cs, and Ba, a phonon band gap was formed between the acoustic and optical branches. The calculated PR indicated that the fillers suppress the acoustic phonon modes and change the energy transport mechanism from propagative to diffusive or localized resulting in "phonon-glass" characteristics. This effect is stronger for the heavy fillers. Furthermore, in all cases, the guest insertion depressed the phonon bandwidth, reduced the Debye temperature, and reduced the phonon group velocity, all of which should lead to reduction of the thermal conductivity.

Joint Acoustic Propagation Experiment (JAPE)

NASA Technical Reports Server (NTRS)

Carnes, Benny L.; Olsen, Robert O.; Kennedy, Bruce W.

1993-01-01

The Joint Acoustic Propagation Experiment (JAPE), performed under the auspices of NATO and the Acoustics Working Group, was conducted at White Sands Missile Range, New Mexico, USA, during the period 11-28 Jul. 1991. JAPE consisted of 220 trials using various acoustic sources including speakers, propane cannon, various types of military vehicles, helicopters, a 155mm howitzer, and static high explosives. Of primary importance to the performance of these tests was the intensive characterization of the atmosphere before and during the trials. Because of the wide range of interests on the part of the participants, JAPE was organized in such a manner to provide a broad cross section of test configurations. These included short and long range propagation from fixed and moving vehicles, terrain masking, and vehicle detection. A number of independent trials were also performed by individual participating agencies using the assets available during JAPE. These tests, while not documented in this report, provided substantial and important data to those groups. Perhaps the most significant feature of JAPE is the establishment of a permanent data base which can be used by not only the participants but by others interested in acoustics. A follow-on test was performed by NASA LaRC during the period 19-29 Aug. 1991 at the same location. These trials consisted of 59 overflights of supersonic aircraft in order to establish the relationship between atmospheric turbulence and the received sonic boom energy at the surface.

Directional asymmetry of the nonlinear wave phenomena in a three-dimensional granular phononic crystal under gravity.

PubMed

Merkel, A; Tournat, V; Gusev, V

2014-08-01

We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption.

Material and Phonon Engineering for Next Generation Acoustic Devices

NASA Astrophysics Data System (ADS)

Kuo, Nai-Kuei

This thesis presents the theoretical and experimental work related to micromachining of low intrinsic loss sapphire and phononic crystals for engineering new classes of electroacoustic devices for frequency control applications. For the first time, a low loss sapphire suspended membrane was fabricated and utilized to form the main body of a piezoelectric lateral overtone bulk acoustic resonator (LOBAR). Since the metalized piezoelectric transducer area in a LOBAR is only a small fraction of the overall resonant cavity (made out of sapphire), high quality factor (Q) overtones are attained. The experiment confirms the low intrinsic mechanical loss of the transferred sapphire thin film, and the resonators exhibit the highest Q of 5,440 at 2.8 GHz ( f·Q of 1.53.1013 Hz). This is also the highest f·Q demonstrated for aluminum-nitride-(AIN)-based Lamb wave devices to date. Beyond demonstrating a low loss device, this experimental work has laid the foundation for the future development of new micromechanical devices based on a high Q, high hardness and chemically resilient material. The search for alternative ways to more efficiently perform frequency control functionalities lead to the exploration of Phononic Crystal (PnC) structures in AIN thin films. Four unit cell designs were theoretically and experimentally investigated to explore the behavior of phononic bandgaps (PBGs) in the ultra high frequency (UHF) range: (i) the conventional square lattice with circular air scatterer, (ii) the inverse acoustic bandgap (IABG) structure, (iii) the fractal PnC, and (iv) the X-shaped PnC. Each unit cell has its unique frequency characteristic that was exploited to synthesize either cavity resonators or improve the performance of acoustic delay lines. The PBGs operate in the range of 770 MHz to 1 GHz and exhibit a maximum acoustic rejection of 40 dB. AIN Lamb wave transducers (LWTs) were employed for the experimental demonstration of the PBGs and cavity resonances. Ultra

Topological Acoustic Delay Line

NASA Astrophysics Data System (ADS)

Zhang, Zhiwang; Tian, Ye; Cheng, Ying; Wei, Qi; Liu, Xiaojun; Christensen, Johan

2018-03-01

Topological protected wave engineering in artificially structured media is at the frontier of ongoing metamaterials research that is inspired by quantum mechanics. Acoustic analogues of electronic topological insulators have recently led to a wealth of new opportunities in manipulating sound propagation with strikingly unconventional acoustic edge modes immune to backscattering. Earlier fabrications of topological insulators are characterized by an unreconfigurable geometry and a very narrow frequency response, which severely hinders the exploration and design of useful devices. Here we establish topologically protected sound in reconfigurable phononic crystals that can be switched on and off simply by rotating its three-legged "atoms" without altering the lattice structure. In particular, we engineer robust phase delay defects that take advantage of the ultrabroadband reflection-free sound propagation. Such topological delay lines serve as a paradigm in compact acoustic devices, interconnects, and electroacoustic integrated circuits.

Nonlinear Acoustics in Cicada Mating Calls Enhance Sound Propagation

DTIC Science & Technology

2009-03-01

NUWC-NPT Reprint Report 11,907 1 March 2009 Nonlinear Acoustics in Cicada Mating Calls Enhance Sound Propagation Derke R. Hughes Albert H...vol. 125, no. 2, February 2009. Nonlinear acoustics in cicada mating calls enhance sound propagation Derke R. Hughes,3 Albert H. Nuttall,h Richard A...2008; revised 31 October 2008; accepted 15 November 2008) An analysis of cicada mating calls, measured in field experiments, indicates that the very

An Expendable Source for Measuring Shallow Water Acoustic Propagation and Geo-Acoustic Bottom Properties

DTIC Science & Technology

2015-09-30

Propagation and Geo -Acoustic Bottom Properties Harry A DeFerrari RSMAS – University of Miami 4600 Rickenbacker Causeway Miami FL. 33149...limited information about the ocean acoustic environment and the geo -acoustic properties of the bottom. The objective here is to measure the pulse...models and estimate the geo -acoustic properties of the bottom by inversion. APPROACH M-sequences have long been the workhorse of basic research

Damping of acoustic flexural phonons in silicene: influence on high-field electronic transport

NASA Astrophysics Data System (ADS)

Rengel, Raúl; Iglesias, José M.; Mokhtar Hamham, El; Martín, María J.

2018-06-01

Silicene is a two-dimensional buckled material with broken horizontal mirror symmetry and Dirac-like dispersion. Under such conditions, flexural acoustic (ZA) phonons play a dominant role. Consequently, it is necessary to consider some suppression mechanism for electron–phonon interactions with long wavelengths in order to reach mobilities useful for electronic applications. In this work, we analyze, by means of an ensemble Monte Carlo simulator, the influence of several possibilities for the description of the effect of ZA phonon damping on electronic transport in silicene. The results show that a hard cutoff situation (total suppression for phonons with a wavelength longer than a critical one), as it has been proposed in the literature, does not yield a realistic picture regarding the electronic distribution function, and it artificially induces a negative differential resistance at moderate and high fields. Sub-parabolic dispersions, on the other hand, may provide a more realistic description in terms of the behavior of the electron distribution in the momentum space, but need extremely short cutoff wavelengths to reach functional mobility and drift velocity values.

Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots

PubMed Central

Vanacore, Giovanni M.; Hu, Jianbo; Liang, Wenxi; Bietti, Sergio; Sanguinetti, Stefano; Carbone, Fabrizio; Zewail, Ahmed H.

2017-01-01

Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dots—grown by Droplet Epitaxy on AlGaAs—with sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible. PMID:28852685

The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

PubMed

Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

2013-10-01

A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

Evidence for anisotropic polar nanoregions in relaxor Pb(Mg1/3Nb2/3)O3: A neutron study of the elastic constants and anomalous TA phonon damping in PMN

NASA Astrophysics Data System (ADS)

Stock, C.; Gehring, P. M.; Hiraka, H.; Swainson, I.; Xu, Guangyong; Ye, Z.-G.; Luo, H.; Li, J.-F.; Viehland, D.

2012-09-01

We use neutron inelastic scattering to characterize the acoustic phonons in the relaxor Pb(Mg1/3Nb2/3)O3 (PMN) and demonstrate the presence of a highly anisotropic damping mechanism that is directly related to short-range polar correlations. For a large range of temperatures above Tc˜210 K, where dynamic, short-range polar correlations are present, acoustic phonons propagating along [11¯0] and polarized along [110] (TA2 phonons) are overdamped and softened across most of the Brillouin zone. By contrast, acoustic phonons propagating along [100] and polarized along [001] (TA1 phonons) are overdamped and softened for a more limited range of wave vectors q. The anisotropy and temperature dependence of the acoustic phonon energy linewidth Γ are directly correlated with neutron diffuse scattering cross section, indicating that polar nanoregions are the cause of the anomalous behavior. The damping and softening vanish for q→0, i.e., for long-wavelength acoustic phonons near the zone center, which supports the notion that the anomalous damping is a result of the coupling between the relaxational component of the diffuse scattering and the harmonic TA phonons. Therefore, these effects are not due to large changes in the elastic constants with temperature because the elastic constants correspond to the long-wavelength limit. We compare the elastic constants we measure to those from Brillouin scattering experiments and to values reported for pure PbTiO3. We show that while the values of C44 are quite similar, those for C11 and C12 are significantly less in PMN and result in a softening of (C11-C12) over PbTiO3. The elastic constants also show an increased elastic anisotropy [2C44/(C11-C12)] in PMN versus that in PbTiO3. These results are suggestive of an instability to TA2 acoustic fluctuations in PMN and other relaxor ferroelectrics. We discuss our results in the context of the current debate over the “waterfall” effect and show that they are inconsistent with

Joint Acoustic Propagation Experiment (JAPE-91) Workshop

NASA Technical Reports Server (NTRS)

Willshire, William L., Jr. (Compiler); Chestnutt, David (Compiler)

1993-01-01

The Joint Acoustic Propagation Experiment (JAPE), was conducted at the White Sands Missile Range, New Mexico, USA, during the period 11-28 Jul. 1991. JAPE consisted of various short and long range propagation experiments using various acoustic sources including speakers, propane cannons, helicopters, a 155 mm howitzer, and static high explosives. Of primary importance to the performance of theses tests was the extensive characterization of the atmosphere during these tests. This atmospheric characterization included turbulence measurements. A workshop to disseminate the results of JAPE-91 was held in Hampton, VA, on 28 Apr. 1993. This report is a compilation of the presentations made at the workshop along with a list of attendees and the agenda.

Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Zhenhua; Yu, Lingyu

The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region nearmore » the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Furthermore, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.« less

Rainbow trapping of ultrasonic guided waves in chirped phononic crystal plates

DOE PAGES

Tian, Zhenhua; Yu, Lingyu

2017-01-05

The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower boundary of a stopband that gradually varies in chirped phononic crystal plates. As guided waves propagate along the phononic crystal plate, waves gradually slow down and finally stop forward propagating. The energy of guided waves is concentrated at the low velocity region nearmore » the stopband. Moreover, the guided wave energy of different frequencies is concentrated at different locations, which manifests as rainbow guided waves. We believe implementing the rainbow trapping will open new paradigms for guiding and focusing of guided waves. Furthermore, the rainbow guided waves with energy concentration and spatial separation of frequencies may have potential applications in nondestructive evaluation, spatial wave filtering, energy harvesting, and acoustofluidics.« less

Numerical investigation of diffraction of acoustic waves by phononic crystals

NASA Astrophysics Data System (ADS)

Moiseyenko, Rayisa P.; Declercq, Nico F.; Laude, Vincent

2012-05-01

Diffraction as well as transmission of acoustic waves by two-dimensional phononic crystals (PCs) composed of steel rods in water are investigated in this paper. The finite element simulations were performed in order to compute pressure fields generated by a line source that are incident on a finite size PC. Such field maps are analyzed based on the complex band structure for the infinite periodic PC. Finite size computations indicate that the exponential decrease of the transmission at deaf frequencies is much stronger than that in Bragg band gaps.

Experiments to investigate the acoustic properties of sound propagation

NASA Astrophysics Data System (ADS)

Dagdeviren, Omur E.

2018-07-01

Propagation of sound waves is one of the fundamental concepts in physics. Some of the properties of sound propagation such as attenuation of sound intensity with increasing distance are familiar to everybody from the experiences of daily life. However, the frequency dependence of sound propagation and the effect of acoustics in confined environments are not straightforward to estimate. In this article, we propose experiments, which can be conducted in a classroom environment with commonly available devices such as smartphones and laptops to measure sound intensity level as a function of the distance between the source and the observer and frequency of the sound. Our experiments and deviations from the theoretical calculations can be used to explain basic concepts of sound propagation and acoustics to a diverse population of students.

Ultrafast switching of valence and generation of coherent acoustic phonons in semiconducting rare-earth monosulfides

NASA Astrophysics Data System (ADS)

Punpongjareorn, Napat; He, Xing; Tang, Zhongjia; Guloy, Arnold M.; Yang, Ding-Shyue

2017-08-01

We report on the ultrafast carrier dynamics and generation of coherent acoustic phonons in YbS, a semiconducting rare-earth monochalcogenide, using two-color pump-probe reflectivity. Compared to the carrier relaxation processes and lifetimes of conventional semiconductors, recombination of photoexcited electrons with holes in localized f orbitals is found to take place rapidly with a density-independent time constant of <500 fs in YbS. Such carrier annihilation signifies the unique and ultrafast nature of valence restoration of ytterbium ions after femtosecond photoexcitation switching. Following transfer of the absorbed energy to the lattice, coherent acoustic phonons emerge on the picosecond timescale as a result of the thermal strain in the photoexcited region. By analyzing the electronic and structural dynamics, we obtain the physical properties of YbS including its two-photon absorption and thermooptic coefficients, the period and decay time of the coherent oscillation, and the sound velocity.

Lamb wave band gaps in a double-sided phononic plate

NASA Astrophysics Data System (ADS)

Wang, Peng; Chen, Tian-Ning; Yu, Kun-Peng; Wang, Xiao-Peng

2013-02-01

In this paper, we report on the theoretical investigation of the propagation characteristics of Lamb wave in a phononic crystal structure constituted by a square array of cylindrical stubs deposited on both sides of a thin homogeneous plate. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are studied by using the finite-element method. We investigate the evolution of band gaps in the double-sided phononic plate with stub height on both sides arranged from an asymmetrical distribution to a symmetrical distribution gradually. Numerical results show that as the double stubs in a unit cell arranged more symmetrically on both sides, band width shifts, new band gaps appear, and the bands become flat due to localized resonant modes which couple with plate modes. Specially, more band gaps and flat bands can be found in the symmetrical system as a result of local resonances of the stubs which interact in a stronger way with the plate modes. Moreover, the symmetrical double-sided plate exhibits lower and smaller band gap than that of the asymmetrical plate. These propagation properties of elastic or acoustic waves in the double-sided plate can potentially be utilized to generate filters, slow the group velocity, low-frequency sound insulation, and design acoustic sensors.

Experiments to Investigate the Acoustic Properties of Sound Propagation

ERIC Educational Resources Information Center

Dagdeviren, Omur E.

2018-01-01

Propagation of sound waves is one of the fundamental concepts in physics. Some of the properties of sound propagation such as attenuation of sound intensity with increasing distance are familiar to everybody from the experiences of daily life. However, the frequency dependence of sound propagation and the effect of acoustics in confined…

Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment

NASA Astrophysics Data System (ADS)

Luo, Jing

Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.

Evidence of Longitudinal Acoustic Phonon Generation in Si Doping Superlattices by Ge Prism-Coupled THz Laser Radiation

NASA Astrophysics Data System (ADS)

Wilson, T.; Kasper, E.; Oehme, M.; Schulze, J.; Korolev, K.

2014-11-01

We report on the direct excitation of 246 GHz longitudinal acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation of the same frequency. A longitudinally polarized evanescent laser light field is coupled to the superlattice through a germanium prism providing total internal reflection at the superlattice interface. The ballistic phonon signal is detected by a superconducting aluminum bolometer. The sample is immersed in low-temperature liquid helium.

Non-reciprocal elastic wave propagation in 2D phononic membranes with spatiotemporally varying material properties

NASA Astrophysics Data System (ADS)

Attarzadeh, M. A.; Nouh, M.

2018-05-01

One-dimensional phononic materials with material fields traveling simultaneously in space and time have been shown to break elastodynamic reciprocity resulting in unique wave propagation features. In the present work, a comprehensive mathematical analysis is presented to characterize and fully predict the non-reciprocal wave dispersion in two-dimensional space. The analytical dispersion relations, in the presence of the spatiotemporal material variations, are validated numerically using finite 2D membranes with a prescribed number of cells. Using omnidirectional excitations at the membrane's center, wave propagations are shown to exhibit directional asymmetry that increases drastically in the direction of the material travel and vanishes in the direction perpendicular to it. The topological nature of the predicted dispersion in different propagation directions are evaluated using the computed Chern numbers. Finally, the degree of the 2D non-reciprocity is quantified using a non-reciprocity index (NRI) which confirms the theoretical dispersion predictions as well as the finite simulations. The presented framework can be extended to plate-type structures as well as 3D spatiotemporally modulated phononic crystals.

The Effects of Sediment Properties on Low Frequency Acoustic Propagation

DTIC Science & Technology

2014-09-30

identified in task (a). c. Understanding the effect of ocean acidification on acoustic propagation. The PIs (Miller and Potty) are trying to get funding...the half-space. The properties of the sediment used in the model calculation are shown in the top panel. b. Effect of Ocean Acidification on...Acoustic Propagation: One of the consequences of increasing atmospheric CO2 is ocean acidification . The reduction in pH is a direct result of increased

Acoustic Propagation Modeling for Marine Hydro-Kinetic Applications

NASA Astrophysics Data System (ADS)

Johnson, C. N.; Johnson, E.

2014-12-01

The combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand. However, in order to deploy and test prototypes, and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines that determine the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. An accurate model for predicting the propagation of a MHK source in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. Paracousti, a finite difference solution to the acoustic equations, was originally developed for sound propagation in atmospheric environments and has been successfully validated for a number of different geophysical activities. The three-dimensional numerical implementation is advantageous over other acoustic propagation techniques for a MHK application where the domains of interest have complex 3D interactions from the seabed, banks, and other shallow water effects. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. This includes a variety of hydrodynamic and physical environments that may be present in a potential MHK application including shallow and deep water, sloping, and canyon type bottoms, with varying sound speed and density profiles. With the model successfully validated for hydro-acoustic environments more complex and realistic MHK sources from turbines and/or arrays can be modeled.

Control of coherent information via on-chip photonic–phononic emitter–receivers

DOE PAGES

Shin, Heedeuk; Cox, Jonathan A.; Jarecki, Robert; ...

2015-03-05

We report that rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon–phonon transduction,more » which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics—which supports GHz frequencies—we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes.« less

Control of coherent information via on-chip photonic-phononic emitter-receivers.

PubMed

Shin, Heedeuk; Cox, Jonathan A; Jarecki, Robert; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T

2015-03-05

Rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon-phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics--which supports GHz frequencies--we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes.

Control of coherent information via on-chip photonic–phononic emitter–receivers

PubMed Central

Shin, Heedeuk; Cox, Jonathan A.; Jarecki, Robert; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T.

2015-01-01

Rapid progress in integrated photonics has fostered numerous chip-scale sensing, computing and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons moving at slower velocities allow information to be stored, filtered and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of integrated photonics. Here we demonstrate a mechanism for coherent information processing based on travelling-wave photon–phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device, physics—which supports GHz frequencies—we create wavelength-insensitive radiofrequency photonic filters with frequency selectivity, narrow-linewidth and high power-handling in silicon. More generally, this emit-receive concept is the impetus for enabling new signal processing schemes. PMID:25740405

Acoustic energy propagation around railways

NASA Astrophysics Data System (ADS)

Cizkova, Petra

2017-09-01

The article deals with the issues of acoustic energy propagation around railways. The research subject was noise emission spreading into the surroundings during the passage of trains over a directly travelled steel bridge construction. Noise emissions were measured using direct measurements in the field. The measurements were performed in two measurement profiles. The noise exposures A LAE measured near the steel bridge construction were compared against the noise exposures A LAE captured on an open track. From the difference of these data, the noise level of the steel bridge structure was determined. Part of the research was to evaluate the effect of the reconstruction of the railway track superstructure on the acoustic situation in the given section of the railway track. The article describes the methodology of measurements, including the processing and evaluation of measured data. The article points out the noise levels of the steel bridge construction and assesses changes in the acoustic situation after the reconstruction.

Acoustic phonons in chrysotile asbestos probed by high-resolution inelastic x-ray scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamontov, Eugene; Vakhrushev, S. B.; Kumzerov, Yu. A,

Acoustic phonons in an individual, oriented fiber of chrysotile asbestos (chemical formula Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}) were observed at room temperature in the inelastic x-ray measurement with a very high (meV) resolution. The x-ray scattering vector was aligned along [1 0 0] direction of the reciprocal lattice, nearly parallel to the long axis of the fiber. The latter coincides with [1 0 0] direction of the direct lattice and the axes of the nano-channels. The data were analyzed using a damped harmonic oscillator model. Analysis of the phonon dispersion in the first Brillouin zone yielded the longitudinal sound velocitymore » of (9200 {+-} 600) m/s.« less

Multicoaxial cylindrical inclusions in locally resonant phononic crystals

NASA Astrophysics Data System (ADS)

Larabi, H.; Pennec, Y.; Djafari-Rouhani, B.; Vasseur, J. O.

2007-06-01

It is known that the transmission spectrum of the so-called locally resonant phononic crystal can exhibit absolute sharp dips in the sonic frequency range due to the resonance scattering of elastic waves. In this paper, we study theoretically, using a finite difference time domain method, the propagation of acoustic waves through a two-dimensional locally resonant crystal in which the matrix is a fluid (such as water) instead of being a solid as in most of the previous papers. The transmission is shown to be dependent upon the fluid or solid nature of the matrix as well as upon the nature of the coating material in contact with the matrix. The other main purpose of this paper is to consider inclusions constituted by coaxial cylindrical multilayers consisting of several alternate shells of a soft material (such as a soft rubber) and a hard material (such as steel). With respect to the usual case of a hard core coated with a soft rubber, the transmission spectrum can exhibit in the same frequency range several peaks instead of one. If two or more phononic crystals are associated together, we find that the structure displays all the zeros of transmission resulting from each individual crystal. Moreover, we show that it is possible to overlap the dips by an appropriate combination of phononic crystals and create a larger acoustic stop band.

Measurement of locally resonant band gaps in a surface phononic crystal with inverted conical pillars

NASA Astrophysics Data System (ADS)

Hsu, Jin-Chen; Lin, Fan-Shun

2018-07-01

In this paper, we numerically and experimentally study locally resonant (LR) band gaps for surface acoustic waves (SAWs) in a honeycomb array of inverted conical pillars grown on the surface of a 128°YX lithium-niobate substrate. We show that the inverted conical pillars can be used to generate lower LR band gaps below the sound cone. This lowering effect is caused by the increase in the effective pillar mass without increasing the effective stiffness. We employ the finite-element method to calculate the LR band gaps and wideband slanted-finger interdigital transducers to measure the transmission of SAWs. Numerical results show that SAWs are prohibited from propagating through the structure in the lowered LR band gaps. Obvious LR band-gap lowering is observed in the experimental result of a surface phononic crystal with a honeycomb array of inverted conical pillars. The results enable enhanced control over the phononic metamaterial and surface structures, which may have applications in low-frequency waveguiding, acoustic isolation, acoustic absorbers, and acoustic filters.

Numerical modelling of nonlinear full-wave acoustic propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velasco-Segura, Roberto, E-mail: roberto.velasco@ccadet.unam.mx; Rendón, Pablo L., E-mail: pablo.rendon@ccadet.unam.mx

2015-10-28

The various model equations of nonlinear acoustics are arrived at by making assumptions which permit the observation of the interaction with propagation of either single or joint effects. We present here a form of the conservation equations of fluid dynamics which are deduced using slightly less restrictive hypothesis than those necessary to obtain the well known Westervelt equation. This formulation accounts for full wave diffraction, nonlinearity, and thermoviscous dissipative effects. A two-dimensional, finite-volume method using Roe’s linearisation has been implemented to obtain numerically the solution of the proposed equations. This code, which has been written for parallel execution on amore » GPU, can be used to describe moderate nonlinear phenomena, at low Mach numbers, in domains as large as 100 wave lengths. Applications range from models of diagnostic and therapeutic HIFU, to parametric acoustic arrays and nonlinear propagation in acoustic waveguides. Examples related to these applications are shown and discussed.« less

Polarization-controlled coherent phonon generation in acoustoplasmonic metasurfaces

NASA Astrophysics Data System (ADS)

Lanzillotti-Kimura, Norberto D.; O'Brien, Kevin P.; Rho, Junsuk; Suchowski, Haim; Yin, Xiaobo; Zhang, Xiang

2018-06-01

Acoustic vibrations at the nanoscale (GHz-THz frequencies) and their interactions with electrons, photons, and other excitations are the heart of an emerging field in physics: nanophononics. The design of ultrahigh frequency acoustic-phonon transducers, with tunable frequency, and easy to integrate in complex systems is still an open and challenging problem for the development of acoustic nanoscopies and phonon lasers. Here we show how an optimized plasmonic metasurface can act as a high-frequency phonon transducer. We report pump-probe experiments in metasurfaces composed of an array of gold nanostructures, revealing that such arrays can act as efficient and tunable photon-phonon transducers, with a strong spectral dependence on the excitation rate and laser polarization. We anticipate our work to be the starting point for the engineering of phononic metasurfaces based on plasmonic nanostructures.

Time-varying phononic crystals

NASA Astrophysics Data System (ADS)

Wright, Derek Warren

The primary objective of this thesis was to gain a deeper understanding of acoustic wave propagation in phononic crystals, particularly those that include materials whose properties can be varied periodically in time. This research was accomplished in three ways. First, a 2D phononic crystal was designed, created, and characterized. Its properties closely matched those determined through simulation. The crystal demonstrated band gaps, dispersion, and negative refraction. It served as a means of elucidating the practicalities of phononic crystal design and construction and as a physical verification of their more interesting properties. Next, the transmission matrix method for analyzing 1D phononic crystals was extended to include the effects of time-varying material parameters. The method was then used to provide a closed-form solution for the case of periodically time-varying material parameters. Some intriguing results from the use of the extended method include dramatically altered transmission properties and parametric amplification. New insights can be gained from the governing equations and have helped to identify the conditions that lead to parametric amplification in these structures. Finally, 2D multiple scattering theory was modified to analyze scatterers with time-varying material parameters. It is shown to be highly compatible with existing multiple scattering theories. It allows the total scattered field from a 2D time-varying phononic crystal to be determined. It was shown that time-varying material parameters significantly affect the phononic crystal transmission spectrum, and this was used to switch an incident monochromatic wave. Parametric amplification can occur under certain circumstances, and this effect was investigated using the closed-form solutions provided by the new 1D method. The complexity of the extended methods grows logarithmically as opposed linearly with existing methods, resulting in superior computational complexity for large

Theoretical models for duct acoustic propagation and radiation

NASA Technical Reports Server (NTRS)

Eversman, Walter

1991-01-01

The development of computational methods in acoustics has led to the introduction of analysis and design procedures which model the turbofan inlet as a coupled system, simultaneously modeling propagation and radiation in the presence of realistic internal and external flows. Such models are generally large, require substantial computer speed and capacity, and can be expected to be used in the final design stages, with the simpler models being used in the early design iterations. Emphasis is given to practical modeling methods that have been applied to the acoustical design problem in turbofan engines. The mathematical model is established and the simplest case of propagation in a duct with hard walls is solved to introduce concepts and terminologies. An extensive overview is given of methods for the calculation of attenuation in uniform ducts with uniform flow and with shear flow. Subsequent sections deal with numerical techniques which provide an integrated representation of duct propagation and near- and far-field radiation for realistic geometries and flight conditions.

Acoustic scattering from phononic crystals with complex geometry.

PubMed

Kulpe, Jason A; Sabra, Karim G; Leamy, Michael J

2016-05-01

This work introduces a formalism for computing external acoustic scattering from phononic crystals (PCs) with arbitrary exterior shape using a Bloch wave expansion technique coupled with the Helmholtz-Kirchhoff integral (HKI). Similar to a Kirchhoff approximation, a geometrically complex PC's surface is broken into a set of facets in which the scattering from each facet is calculated as if it was a semi-infinite plane interface in the short wavelength limit. When excited by incident radiation, these facets introduce wave modes into the interior of the PC. Incorporation of these modes in the HKI, summed over all facets, then determines the externally scattered acoustic field. In particular, for frequencies in a complete bandgap (the usual operating frequency regime of many PC-based devices and the requisite operating regime of the presented theory), no need exists to solve for internal reflections from oppositely facing edges and, thus, the total scattered field can be computed without the need to consider internal multiple scattering. Several numerical examples are provided to verify the presented approach. Both harmonic and transient results are considered for spherical and bean-shaped PCs, each containing over 100 000 inclusions. This facet formalism is validated by comparison to an existing self-consistent scattering technique.

Acoustic wave propagation in high-pressure system.

PubMed

Foldyna, Josef; Sitek, Libor; Habán, Vladimír

2006-12-22

Recently, substantial attention is paid to the development of methods of generation of pulsations in high-pressure systems to produce pulsating high-speed water jets. The reason is that the introduction of pulsations into the water jets enables to increase their cutting efficiency due to the fact that the impact pressure (so-called water-hammer pressure) generated by an impact of slug of water on the target material is considerably higher than the stagnation pressure generated by corresponding continuous jet. Special method of pulsating jet generation was developed and tested extensively under the laboratory conditions at the Institute of Geonics in Ostrava. The method is based on the action of acoustic transducer on the pressure liquid and transmission of generated acoustic waves via pressure system to the nozzle. The purpose of the paper is to present results obtained during the research oriented at the determination of acoustic wave propagation in high-pressure system. The final objective of the research is to solve the problem of transmission of acoustic waves through high-pressure water to generate pulsating jet effectively even at larger distances from the acoustic source. In order to be able to simulate numerically acoustic wave propagation in the system, it is necessary among others to determine dependence of the sound speed and second kinematical viscosity on operating pressure. Method of determination of the second kinematical viscosity and speed of sound in liquid using modal analysis of response of the tube filled with liquid to the impact was developed. The response was measured by pressure sensors placed at both ends of the tube. Results obtained and presented in the paper indicate good agreement between experimental data and values of speed of sound calculated from so-called "UNESCO equation". They also show that the value of the second kinematical viscosity of water depends on the pressure.

Activity-induced instability of phonons in 1D microfluidic crystals.

PubMed

Tsang, Alan Cheng Hou; Shelley, Michael J; Kanso, Eva

2018-02-14

One-dimensional crystals of passively-driven particles in microfluidic channels exhibit collective vibrational modes reminiscent of acoustic 'phonons'. These phonons are induced by the long-range hydrodynamic interactions among the particles and are neutrally stable at the linear level. Here, we analyze the effect of particle activity - self-propulsion - on the emergence and stability of these phonons. We show that the direction of wave propagation in active crystals is sensitive to the intensity of the background flow. We also show that activity couples, at the linear level, transverse waves to the particles' rotational motion, inducing a new mode of instability that persists in the limit of large background flow, or, equivalently, vanishingly small activity. We then report a new phenomenon of phonons switching back and forth between two adjacent crystals in both passively-driven and active systems, similar in nature to the wave switching observed in quantum mechanics, optical communication, and density stratified fluids. These findings could have implications for the design of commercial microfluidic systems and the self-assembly of passive and active micro-particles into one-dimensional structures.

Band structure analysis of leaky Bloch waves in 2D phononic crystal plates.

PubMed

Mazzotti, Matteo; Miniaci, Marco; Bartoli, Ivan

2017-02-01

A hybrid Finite Element-Plane Wave Expansion method is presented for the band structure analysis of phononic crystal plates with two dimensional lattice that are in contact with acoustic half-spaces. The method enables the computation of both real (propagative) and imaginary (attenuation) components of the Bloch wavenumber at any given frequency. Three numerical applications are presented: a benchmark dispersion analysis for an oil-loaded Titanium isotropic plate, the band structure analysis of a water-loaded Tungsten slab with square cylindrical cavities and a phononic crystal plate composed of Aurum cylinders embedded in an epoxy matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

Linear and non-linear infrared response of one-dimensional vibrational Holstein polarons in the anti-adiabatic limit: Optical and acoustical phonon models

NASA Astrophysics Data System (ADS)

Falvo, Cyril

2018-02-01

The theory of linear and non-linear infrared response of vibrational Holstein polarons in one-dimensional lattices is presented in order to identify the spectral signatures of self-trapping phenomena. Using a canonical transformation, the optical response is computed from the small polaron point of view which is valid in the anti-adiabatic limit. Two types of phonon baths are considered: optical phonons and acoustical phonons, and simple expressions are derived for the infrared response. It is shown that for the case of optical phonons, the linear response can directly probe the polaron density of states. The model is used to interpret the experimental spectrum of crystalline acetanilide in the C=O range. For the case of acoustical phonons, it is shown that two bound states can be observed in the two-dimensional infrared spectrum at low temperature. At high temperature, analysis of the time-dependence of the two-dimensional infrared spectrum indicates that bath mediated correlations slow down spectral diffusion. The model is used to interpret the experimental linear-spectroscopy of model α-helix and β-sheet polypeptides. This work shows that the Davydov Hamiltonian cannot explain the observations in the NH stretching range.

Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO 2

DOE PAGES

Lan, Tian; Li, Chen W.; Hellman, O.; ...

2015-08-11

Although the rutile structure of TiO 2 is stable at high temperatures, the conventional quasiharmonic approximation predicts that several acoustic phonons decrease anomalously to zero frequency with thermal expansion, incorrectly predicting a structural collapse at temperatures well below 1000 K. In this paper, inelastic neutron scattering was used to measure the temperature dependence of the phonon density of states (DOS) of rutile TiO 2 from 300 to 1373 K. Surprisingly, these anomalous acoustic phonons were found to increase in frequency with temperature. First-principles calculations showed that with lattice expansion, the potentials for the anomalous acoustic phonons transform from quadratic tomore » quartic, stabilizing the rutile phase at high temperatures. In these modes, the vibrational displacements of adjacent Ti and O atoms cause variations in hybridization of 3d electrons of Ti and 2p electrons of O atoms. Finally, with thermal expansion, the energy variation in this “phonon-tracked hybridization” flattens the bottom of the interatomic potential well between Ti and O atoms, and induces a quarticity in the phonon potential.« less

Designing Phononic Crystals with Wide and Robust Band Gaps

NASA Astrophysics Data System (ADS)

Jia, Zian; Chen, Yanyu; Yang, Haoxiang; Wang, Lifeng

2018-04-01

Phononic crystals (PnCs) engineered to manipulate and control the propagation of mechanical waves have enabled the design of a range of novel devices, such as waveguides, frequency modulators, and acoustic cloaks, for which wide and robust phononic band gaps are highly preferable. While numerous PnCs have been designed in recent decades, to the best of our knowledge, PnCs that possess simultaneous wide and robust band gaps (to randomness and deformations) have not yet been reported. Here, we demonstrate that by combining the band-gap formation mechanisms of Bragg scattering and local resonances (the latter one is dominating), PnCs with wide and robust phononic band gaps can be established. The robustness of the phononic band gaps are then discussed from two aspects: robustness to geometric randomness (manufacture defects) and robustness to deformations (mechanical stimuli). Analytical formulations further predict the optimal design parameters, and an uncertainty analysis quantifies the randomness effect of each designing parameter. Moreover, we show that the deformation robustness originates from a local resonance-dominant mechanism together with the suppression of structural instability. Importantly, the proposed PnCs require only a small number of layers of elements (three unit cells) to obtain broad, robust, and strong attenuation bands, which offer great potential in designing flexible and deformable phononic devices.

The Effects of Sediment Properties on Low Frequency Acoustic Propagation

DTIC Science & Technology

2013-09-30

Ballroom Music Spillover into a Beluga Whale Aquarium Exhibit,” Advances in Acoustics and Vibration, 2012 (doi:10.1155/2012/402130) [ refereed]. 12... Acoustic Propagation James H. Miller and Gopu R. Potty University of Rhode Island Department of Ocean Engineering Narragansett, RI 02881 Phone (401...investigations have indicated that water-borne acoustic arrival properties such as their Airy Phase are sensitive to sediment shear properties. Our major

Toward a Nonlinear Acoustic Analogy: Turbulence as a Source of Sound and Nonlinear Propagation

NASA Technical Reports Server (NTRS)

Miller, Steven A. E.

2015-01-01

An acoustic analogy is proposed that directly includes nonlinear propagation effects. We examine the Lighthill acoustic analogy and replace the Green's function of the wave equation with numerical solutions of the generalized Burgers' equation. This is justified mathematically by using similar arguments that are the basis of the solution of the Lighthill acoustic analogy. This approach is superior to alternatives because propagation is accounted for directly from the source to the far-field observer instead of from an arbitrary intermediate point. Validation of a numerical solver for the generalized Burgers' equation is performed by comparing solutions with the Blackstock bridging function and measurement data. Most importantly, the mathematical relationship between the Navier- Stokes equations, the acoustic analogy that describes the source, and canonical nonlinear propagation equations is shown. Example predictions are presented for nonlinear propagation of jet mixing noise at the sideline angle

Toward a Nonlinear Acoustic Analogy: Turbulence as a Source of Sound and Nonlinear Propagation

NASA Technical Reports Server (NTRS)

Miller, Steven A. E.

2015-01-01

An acoustic analogy is proposed that directly includes nonlinear propagation effects. We examine the Lighthill acoustic analogy and replace the Green's function of the wave equation with numerical solutions of the generalized Burgers' equation. This is justified mathematically by using similar arguments that are the basis of the solution of the Lighthill acoustic analogy. This approach is superior to alternatives because propagation is accounted for directly from the source to the far-field observer instead of from an arbitrary intermediate point. Validation of a numerical solver for the generalized Burgers' equation is performed by comparing solutions with the Blackstock bridging function and measurement data. Most importantly, the mathematical relationship between the Navier-Stokes equations, the acoustic analogy that describes the source, and canonical nonlinear propagation equations is shown. Example predictions are presented for nonlinear propagation of jet mixing noise at the sideline angle.

Thermal transport and anharmonic phonons in strained monolayer hexagonal boron nitride

NASA Astrophysics Data System (ADS)

Li, Shasha; Chen, Yue

2017-03-01

Thermal transport and phonon-phonon coupling in monolayer hexagonal boron nitride (h-BN) under equibiaxial strains are investigated from first principles. Phonon spectra at elevated temperatures have been calculated from perturbation theory using the third-order anharmonic force constants. The stiffening of the out-of-plane transverse acoustic mode (ZA) near the Brillouin zone center and the increase of acoustic phonon lifetimes are found to contribute to the dramatic increase of thermal transport in strained h-BN. The transverse optical mode (TO) at the K point, which was predicted to lead to mechanical failure of h-BN, is found to shift to lower frequencies at elevated temperatures under equibiaxial strains. The longitudinal and transverse acoustic modes exhibit broad phonon spectra under large strains in sharp contrast to the ZA mode, indicating strong in-plane phonon-phonon coupling.

Renormalisation of Nonequilibrium Phonons Under Strong Perturbative Influences.

NASA Astrophysics Data System (ADS)

Mehta, Sushrut Madhukar

Effects of strong perturbative influences, namely the presence of a narrow distribution of acoustic phonons, and the presence of an electron plasma, on the dynamics of nonequilibrium, near zone center, longitudinal optical phonons in GaP have been investigated in two separate experiments. The study of the effects of the interaction between the LO phonons and a heavily populated, narrow distribution of acoustic phonons lead to the observation of a new optically driven nonequilibrium phonon state. Time Resolved Coherent Antistokes Raman Scattering (TR-CARS), with picosecond resolution, was used to investigate the new mode. In order to achieve high occupation numbers in the acoustic branch, the picosecond laser pulses used were amplified up to 1.0 GW/cm^2 peak power per laser beam. An important characteristic property of the new state which differentiates it from the well known LO phonon state is the fact that rather than having the single decay rate observed under thermal equilibrium, the new state has two decay rates. Moreover, these two decay rates depend strongly on the distribution of the acoustic phonon occupation number. The coupling of the LO phonons with an electron plasma, on the other hand, was investigated by measurements of the shape of the Raman scattered line associated with the phonon-plasmon coupled mode. The plasma was generated by thermal excitation of carriers in doped samples. It was possible to study a large variety of plasma excitations by controlling the concentration of the dopant and the ambient temperature. A complete, self consistant model based on standard dielectric response theory is presented, and applied to the measurements of the phonon-plasmon coupled mode. It is possible to recover, via this model, the effective coupled mode damping rate, the plasma damping rate, and the plasma frequency as functions of ambient temperature, or the carrier concentration.

Phononic crystal diffraction gratings

NASA Astrophysics Data System (ADS)

Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

2012-02-01

When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

Infrasound propagation in tropospheric ducts and acoustic shadow zones.

PubMed

de Groot-Hedlin, Catherine D

2017-10-01

Numerical computations of the Navier-Stokes equations governing acoustic propagation are performed to investigate infrasound propagation in the troposphere and into acoustic shadow zones. An existing nonlinear finite-difference, time-domain (FDTD) solver that constrains input sound speed models to be axisymmetric is expanded to allow for advection and rigid, stair-step topography. The FDTD solver permits realistic computations along a given azimuth. It is applied to several environmental models to examine the effects of nonlinearity, topography, advection, and two-dimensional (2D) variations in wind and sound speeds on the penetration of infrasound into shadow zones. Synthesized waveforms are compared to a recording of a rocket motor fuel elimination event at the Utah Test and Training Range. Results show good agreement in the amplitude, duration, and spectra of synthesized and recorded waveforms for propagation through 2D atmospheric models whether or not topography, advection, or nonlinearity is explicitly included. However, infrasound propagation through a one-dimensional, range-averaged, atmospheric model yields waveforms with lower amplitudes and frequencies, suggesting that small-scale atmospheric variability causes significant scatter within the troposphere, leading to enhanced infrasound penetration into shadow zones. Thus, unresolved fine-scale atmospheric dynamics are not required to explain infrasound propagation into shadow zones.

Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

PubMed

Ma, Tian-Xue; Zou, Kui; Wang, Yue-Sheng; Zhang, Chuanzeng; Su, Xiao-Xing

2014-11-17

Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode.

Acoustic Environment of Haro Strait: Preliminary Propagation Modeling and Data Analysis

DTIC Science & Technology

2006-08-01

the frequency range 1–10 kHz are combined to analyze the acoustic environment of Haro Strait of Puget Sound , an area frequented by the southern...51Haro Strait, Puget Sound , acoustic environment, shallow water, acoustic model, southern resident killer whales, shipping noise Field measurements and...acoustic propagation modeling for the frequency range 1–10 kHz are combined to analyze the acous- tic environment of Haro Strait of Puget Sound , home to

Parabolic equation for nonlinear acoustic wave propagation in inhomogeneous moving media

NASA Astrophysics Data System (ADS)

Aver'yanov, M. V.; Khokhlova, V. A.; Sapozhnikov, O. A.; Blanc-Benon, Ph.; Cleveland, R. O.

2006-12-01

A new parabolic equation is derived to describe the propagation of nonlinear sound waves in inhomogeneous moving media. The equation accounts for diffraction, nonlinearity, absorption, scalar inhomogeneities (density and sound speed), and vectorial inhomogeneities (flow). A numerical algorithm employed earlier to solve the KZK equation is adapted to this more general case. A two-dimensional version of the algorithm is used to investigate the propagation of nonlinear periodic waves in media with random inhomogeneities. For the case of scalar inhomogeneities, including the case of a flow parallel to the wave propagation direction, a complex acoustic field structure with multiple caustics is obtained. Inclusion of the transverse component of vectorial random inhomogeneities has little effect on the acoustic field. However, when a uniform transverse flow is present, the field structure is shifted without changing its morphology. The impact of nonlinearity is twofold: it produces strong shock waves in focal regions, while, outside the caustics, it produces higher harmonics without any shocks. When the intensity is averaged across the beam propagating through a random medium, it evolves similarly to the intensity of a plane nonlinear wave, indicating that the transverse redistribution of acoustic energy gives no considerable contribution to nonlinear absorption.

Probing Thermomechanics at the Nanoscale: Impulsively Excited Pseudosurface Acoustic Waves in Hypersonic Phononic Crystals

PubMed Central

2011-01-01

High-frequency surface acoustic waves can be generated by ultrafast laser excitation of nanoscale patterned surfaces. Here we study this phenomenon in the hypersonic frequency limit. By modeling the thermomechanics from first-principles, we calculate the system’s initial heat-driven impulsive response and follow its time evolution. A scheme is introduced to quantitatively access frequencies and lifetimes of the composite system’s excited eigenmodes. A spectral decomposition of the calculated response on the eigemodes of the system reveals asymmetric resonances that result from the coupling between surface and bulk acoustic modes. This finding allows evaluation of impulsively excited pseudosurface acoustic wave frequencies and lifetimes and expands our understanding of the scattering of surface waves in mesoscale metamaterials. The model is successfully benchmarked against time-resolved optical diffraction measurements performed on one-dimensional and two-dimensional surface phononic crystals, probed using light at extreme ultraviolet and near-infrared wavelengths. PMID:21910426

Experimental demonstration of topologically protected efficient sound propagation in an acoustic waveguide network

NASA Astrophysics Data System (ADS)

Wei, Qi; Tian, Ye; Zuo, Shu-Yu; Cheng, Ying; Liu, Xiao-Jun

2017-03-01

Acoustic topological states support sound propagation along the boundary in a one-way direction with inherent robustness against defects and disorders, leading to the revolution of the manipulation on acoustic waves. A variety of acoustic topological states relying on circulating fluid, chiral coupling, or temporal modulation have been proposed theoretically. However, experimental demonstration has so far remained a significant challenge, due to the critical limitations such as structural complexity and high losses. Here, we experimentally demonstrate an acoustic anomalous Floquet topological insulator in a waveguide network. The acoustic gapless edge states can be found in the band gap when the waveguides are strongly coupled. The scheme features simple structure and high-energy throughput, leading to the experimental demonstration of efficient and robust topologically protected sound propagation along the boundary. The proposal may offer a unique, promising application for design of acoustic devices in acoustic guiding, switching, isolating, filtering, etc.

Phonon spectra and the one-phonon and two-phonon densities of states of UO2 and PuO2

NASA Astrophysics Data System (ADS)

Poplavnoi, A. S.; Fedorova, T. P.; Fedorov, I. A.

2017-04-01

The vibrational spectra of uranium dioxide UO2 and plutonium dioxide PuO2, as well as the one-phonon densities of states and thermal occupation number weighted two-phonon densities of states, have been calculated within the framework of the phenomenological rigid ion model. It has been shown that the acoustic and optical branches of the spectra are predominantly determined by vibrations of the metal and oxygen atoms, respectively, because the atomic masses of the metal and oxygen differ from each other by an order of magnitude. On this basis, the vibrational spectra can be represented in two Brillouin zones, i.e., in the Brillouin zone of the crystal and the Brillouin zone of the oxygen sublattice. In this case, the number of optical branches decreases by a factor of two. The two-phonon densities of states consist of two broad structured peaks. The temperature dependences of the upper peak exhibit a thermal broadening of the phonon lines L01 and L02 in the upper part of the optical branches. The lower peak is responsible for the thermal broadening of the lowest two optical (T02, T01) and acoustic (LA, TA) branches.

Acoustic Propagation Modeling in Shallow Water

DTIC Science & Technology

1996-10-01

Oceanography La Jolla, California 92093-0701 (Received April 15, 1996) This paper provides references for the Navy’s existing databases . Various...a compilation of many aspects of high-frequency (OAML) contains a description of Navy models and acoustics. databases . The Navy’s use of shallow...become significant because the propagation path may involve many tens of bounces. A description of a reflectivity database is (b) Geometry for the

Engineering dissipation with phononic spectral hole burning

NASA Astrophysics Data System (ADS)

Behunin, R. O.; Kharel, P.; Renninger, W. H.; Rakich, P. T.

2017-03-01

Optomechanics, nano-electromechanics, and integrated photonics have brought about a renaissance in phononic device physics and technology. Central to this advance are devices and materials supporting ultra-long-lived photonic and phononic excitations that enable novel regimes of classical and quantum dynamics based on tailorable photon-phonon coupling. Silica-based devices have been at the forefront of such innovations for their ability to support optical excitations persisting for nearly 1 billion cycles, and for their low optical nonlinearity. While acoustic phonon modes can persist for a similar number of cycles in crystalline solids at cryogenic temperatures, it has not been possible to achieve such performance in silica, as silica becomes acoustically opaque at low temperatures. We demonstrate that these intrinsic forms of phonon dissipation are greatly reduced (by >90%) by nonlinear saturation using continuous drive fields of disparate frequencies. The result is a form of steady-state phononic spectral hole burning that produces a wideband transparency window with optically generated phonon fields of modest (nW) powers. We developed a simple model that explains both dissipative and dispersive changes produced by phononic saturation. Our studies, conducted in a microscale device, represent an important step towards engineerable phonon dynamics on demand and the use of glasses as low-loss phononic media.

Designing Phononic Crystals with Wide and Robust Band Gaps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Zian; Chen, Yanyu; Yang, Haoxiang

Here, phononic crystals (PnCs) engineered to manipulate and control the propagation of mechanical waves have enabled the design of a range of novel devices, such as waveguides, frequency modulators, and acoustic cloaks, for which wide and robust phononic band gaps are highly preferable. While numerous PnCs have been designed in recent decades, to the best of our knowledge, PnCs that possess simultaneous wide and robust band gaps (to randomness and deformations) have not yet been reported. Here, we demonstrate that by combining the band-gap formation mechanisms of Bragg scattering and local resonances (the latter one is dominating), PnCs with widemore » and robust phononic band gaps can be established. The robustness of the phononic band gaps are then discussed from two aspects: robustness to geometric randomness (manufacture defects) and robustness to deformations (mechanical stimuli). Analytical formulations further predict the optimal design parameters, and an uncertainty analysis quantifies the randomness effect of each designing parameter. Moreover, we show that the deformation robustness originates from a local resonance-dominant mechanism together with the suppression of structural instability. Importantly, the proposed PnCs require only a small number of layers of elements (three unit cells) to obtain broad, robust, and strong attenuation bands, which offer great potential in designing flexible and deformable phononic devices.« less

Designing Phononic Crystals with Wide and Robust Band Gaps

DOE PAGES

Jia, Zian; Chen, Yanyu; Yang, Haoxiang; ...

2018-04-16

Here, phononic crystals (PnCs) engineered to manipulate and control the propagation of mechanical waves have enabled the design of a range of novel devices, such as waveguides, frequency modulators, and acoustic cloaks, for which wide and robust phononic band gaps are highly preferable. While numerous PnCs have been designed in recent decades, to the best of our knowledge, PnCs that possess simultaneous wide and robust band gaps (to randomness and deformations) have not yet been reported. Here, we demonstrate that by combining the band-gap formation mechanisms of Bragg scattering and local resonances (the latter one is dominating), PnCs with widemore » and robust phononic band gaps can be established. The robustness of the phononic band gaps are then discussed from two aspects: robustness to geometric randomness (manufacture defects) and robustness to deformations (mechanical stimuli). Analytical formulations further predict the optimal design parameters, and an uncertainty analysis quantifies the randomness effect of each designing parameter. Moreover, we show that the deformation robustness originates from a local resonance-dominant mechanism together with the suppression of structural instability. Importantly, the proposed PnCs require only a small number of layers of elements (three unit cells) to obtain broad, robust, and strong attenuation bands, which offer great potential in designing flexible and deformable phononic devices.« less

Phonon cross-plane transport and thermal boundary resistance: effect of heat source size and thermal boundary resistance on phonon characteristics

NASA Astrophysics Data System (ADS)

Ali, H.; Yilbas, B. S.

2016-09-01

Phonon cross-plane transport across silicon and diamond thin films pair is considered, and thermal boundary resistance across the films pair interface is examined incorporating the cut-off mismatch and diffusive mismatch models. In the cut-off mismatch model, phonon frequency mismatch for each acoustic branch is incorporated across the interface of the silicon and diamond films pair in line with the dispersion relations of both films. The frequency-dependent and transient solution of the Boltzmann transport equation is presented, and the equilibrium phonon intensity ratios at the silicon and diamond film edges are predicted across the interface for each phonon acoustic branch. Temperature disturbance across the edges of the films pair is incorporated to assess the phonon transport characteristics due to cut-off and diffusive mismatch models across the interface. The effect of heat source size, which is allocated at high-temperature (301 K) edge of the silicon film, on the phonon transport characteristics at the films pair interface is also investigated. It is found that cut-off mismatch model predicts higher values of the thermal boundary resistance across the films pair interface as compared to that of the diffusive mismatch model. The ratio of equilibrium phonon intensity due to the cut-off mismatch over the diffusive mismatch models remains >1 at the silicon edge, while it becomes <1 at the diamond edge for all acoustic branches.

Band structures in a two-dimensional phononic crystal with rotational multiple scatterers

NASA Astrophysics Data System (ADS)

Song, Ailing; Wang, Xiaopeng; Chen, Tianning; Wan, Lele

2017-03-01

In this paper, the acoustic wave propagation in a two-dimensional phononic crystal composed of rotational multiple scatterers is investigated. The dispersion relationships, the transmission spectra and the acoustic modes are calculated by using finite element method. In contrast to the system composed of square tubes, there exist a low-frequency resonant bandgap and two wide Bragg bandgaps in the proposed structure, and the transmission spectra coincide with band structures. Specially, the first bandgap is based on locally resonant mechanism, and the simulation results agree well with the results of electrical circuit analogy. Additionally, increasing the rotation angle can remarkably influence the band structures due to the transfer of sound pressure between the internal and external cavities in low-order modes, and the redistribution of sound pressure in high-order modes. Wider bandgaps are obtained in arrays composed of finite unit cells with different rotation angles. The analysis results provide a good reference for tuning and obtaining wide bandgaps, and hence exploring the potential applications of the proposed phononic crystal in low-frequency noise insulation.

Deep seafloor arrivals in long range ocean acoustic propagation.

PubMed

Stephen, Ralph A; Bolmer, S Thompson; Udovydchenkov, Ilya A; Worcester, Peter F; Dzieciuch, Matthew A; Andrew, Rex K; Mercer, James A; Colosi, John A; Howe, Bruce M

2013-10-01

Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These "deep seafloor" arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor.

An analysis of phonon emission as controlled by the combined interaction with the acoustic and piezoelectric phonons in a degenerate III-V compound semiconductor using an approximated Fermi-Dirac distribution at low lattice temperatures

NASA Astrophysics Data System (ADS)

Basu, A.; Das, B.; Middya, T. R.; Bhattacharya, D. P.

2018-03-01

Compound semiconductors being piezoelectric in nature, the intrinsic thermal vibration of the lattice atoms at any temperature gives rise to an additional potential field that perturbs the periodic potential field of the atoms. This is over and above the intrinsic deformation acoustic potential field which is always produced in every material. The scattering of the electrons through the piezoelectric perturbing potential is important in all compound semiconductors, particularly at the low lattice temperatures. Thus, the electrical transport in such materials is principally controlled by the combined interaction of the electrons with the deformation potential acoustic and piezoelectric phonons at low lattice temperatures. The study here, deals with the problem of phonon growth characteristics, considering the combined scattering of the non-equilibrium electrons in compound semiconductors, at low lattice temperatures. Beside degeneracy, other low temperature features, like the inelasticity of the electron-phonon collisions, and the full form of the phonon distribution have been duly considered. The distribution function of the degenerate ensemble of carriers, as given by the heated Fermi-Dirac function, has been approximated by a simplified, well-tested model. The model which has been proposed earlier, makes it much easier to carry out analytically the integrations without usual oversimplified approximations.

Tunable Acoustic Valley-Hall Edge States in Reconfigurable Phononic Elastic Waveguides

NASA Astrophysics Data System (ADS)

Liu, Ting-Wei; Semperlotti, Fabio

2018-01-01

We investigate the occurrence of acoustic topological edge states in a 2D phononic elastic waveguide due to a phenomenon that is the acoustic analog of the quantum valley Hall effect. We show that a topological transition takes place between two lattices having broken space-inversion symmetry due to the application of a tunable strain field. This condition leads to the formation of gapless edge states at the domain walls, as further illustrated by the analysis of the bulk-edge correspondence and of the associated topological invariants. Interestingly, topological edge states can also be triggered at the boundary of a single domain, when boundary conditions are properly selected. We also show that the static modulation of the strain field allows us to tune the response of the material between the different supported edge states. Although time-reversal symmetry is still intact in this material system, the edge states are topologically protected when intervalley mixing is either weak or negligible. This characteristic enables selective valley injection, which is achieved via synchronized source strategy.

Development of an acoustic filter for parametric loudspeaker using phononic crystals.

PubMed

Ji, Peifeng; Hu, Wenlin; Yang, Jun

2016-04-01

The spurious signal generated as a result of nonlinearity at the receiving system affects the measurement of the difference-frequency sound in the parametric loudspeaker, especially in the nearfield or near the beam axis. In this paper, an acoustic filter is designed using phononic crystals and its theoretical simulations are carried out by quasi-one- and two-dimensional models with Comsol Multiphysics. According to the simulated transmission loss (TL), an acoustic filter is prototyped consisting of 5×7 aluminum alloy cylinders and its performance is verified experimentally. There is good agreement with the simulation result for TL. After applying our proposed filter in the axial measurement of the parametric loudspeaker, a clear frequency dependence from parametric array effect is detected, which exhibits a good match with the well-known theory described by the Gaussian-beam expansion technique. During the directivity measurement for the parametric loudspeaker, the proposed filter has also proved to be effective and is only needed for small angles. Copyright © 2016 Elsevier B.V. All rights reserved.

Phonons in a magnetized Coulomb crystal of ions with polarizable electron background

NASA Astrophysics Data System (ADS)

Baiko, D. A.; Kozhberov, A. A.

2017-11-01

We have studied phonon modes of a body-centered cubic (bcc) Coulomb crystal of ions in the presence of a uniform magnetic field B taking into account the polarizability of the electron background (electron screening) described by the Thomas-Fermi formalism. For k ≫κTF (k and κTF are the phonon wavevector and Thomas-Fermi wavenumber, respectively), electron polarizability is not important. At k ≪κTF , the electron response results in a pronounced effect. One of the three available modes is acoustic. For orthogonal propagation ( k ⊥B ), its frequency Ω is independent of B and κTF . For k ∥B , Ω∝1 /κTF and is independent of B. Another mode is quadratic. Its frequency is ∝1 /(B κTF) for orthogonal propagation and ∝1 /B and independent of κTF for the parallel case. The third mode is optic with Ω≈ωB ( ωB is the ion cyclotron frequency). A general expression is derived for the dynamic matrix of a Coulomb crystal with a polarizable background and more than one ion in the primitive cell. It is employed for a study of a magnetized hexagonal close-packed Coulomb crystal. We have also presented an analysis of phonon polarization vectors in a magnetized bcc crystal with or without screening. The results obtained can be used for realistic calculations of electron-phonon scattering rates and electron thermal and electrical conductivities in neutron star crusts.

Numerical and experimental study of Lamb wave propagation in a two-dimensional acoustic black hole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Shiling; Shen, Zhonghua, E-mail: shenzh@njust.edu.cn; Lomonosov, Alexey M.

2016-06-07

The propagation of laser-generated Lamb waves in a two-dimensional acoustic black-hole structure was studied numerically and experimentally. The geometrical acoustic theory has been applied to calculate the beam trajectories in the region of the acoustic black hole. The finite element method was also used to study the time evolution of propagating waves. An optical system based on the laser-Doppler vibration method was assembled. The effect of the focusing wave and the reduction in wave speed of the acoustic black hole has been validated.

Propagation of acoustic shock waves between parallel rigid boundaries and into shadow zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desjouy, C., E-mail: cyril.desjouy@gmail.com; Ollivier, S.; Dragna, D.

2015-10-28

The study of acoustic shock propagation in complex environments is of great interest for urban acoustics, but also for source localization, an underlying problematic in military applications. To give a better understanding of the phenomenon taking place during the propagation of acoustic shocks, laboratory-scale experiments and numerical simulations were performed to study the propagation of weak shock waves between parallel rigid boundaries, and into shadow zones created by corners. In particular, this work focuses on the study of the local interactions taking place between incident, reflected, and diffracted waves according to the geometry in both regular or irregular – alsomore » called Von Neumann – regimes of reflection. In this latter case, an irregular reflection can lead to the formation of a Mach stem that can modify the spatial distribution of the acoustic pressure. Short duration acoustic shock waves were produced by a 20 kilovolts electric spark source and a schlieren optical method was used to visualize the incident shockfront and the reflection/diffraction patterns. Experimental results are compared to numerical simulations based on the high-order finite difference solution of the two dimensional Navier-Stokes equations.« less

Estimating propagation velocity through a surface acoustic wave sensor

DOEpatents

Xu, Wenyuan; Huizinga, John S.

2010-03-16

Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.

Phonon dynamics of graphene on metals

NASA Astrophysics Data System (ADS)

Taleb, Amjad Al; Farías, Daniel

2016-03-01

The study of surface phonon dispersion curves is motivated by the quest for a detailed understanding of the forces between the atoms at the surface and in the bulk. In the case of graphene, additional motivation comes from the fact that thermal conductivity is dominated by contributions from acoustic phonons, while optical phonon properties are essential to understand Raman spectra. In this article, we review recent progress made in the experimental determination of phonon dispersion curves of graphene grown on several single-crystal metal surfaces. The two main experimental techniques usually employed are high-resolution electron energy loss spectroscopy (HREELS) and inelastic helium atom scattering (HAS). The different dispersion branches provide a detailed insight into the graphene-substrate interaction. Softening of optical modes and signatures of the substrate‧s Rayleigh wave are observed for strong graphene-substrate interactions, while acoustic phonon modes resemble those of free-standing graphene for weakly interacting systems. The latter allows determining the bending rigidity and the graphene-substrate coupling strength. A comparison between theory and experiment is discussed for several illustrative examples. Perspectives for future experiments are discussed.

Phonons and elasticity of cementite through the Curie temperature

NASA Astrophysics Data System (ADS)

Mauger, L.; Herriman, J. E.; Hellman, O.; Tracy, S. J.; Lucas, M. S.; Muñoz, J. A.; Xiao, Yuming; Li, J.; Fultz, B.

2017-01-01

Phonon partial densities of states (pDOS) of Fe573C were measured from cryogenic temperatures through the Curie transition at 460 K using nuclear resonant inelastic x-ray scattering. The cementite pDOS reveal that low-energy acoustic phonons shift to higher energies (stiffen) with temperature before the magnetic transition. This unexpected stiffening suggests strongly nonharmonic vibrational behavior that impacts the thermodynamics and elastic properties of cementite. Density functional theory calculations reproduced the anomalous stiffening observed experimentally in cementite by accounting for phonon-phonon interactions at finite temperatures. The calculations show that the low-energy acoustic phonon branches with polarizations along the [010] direction are largely responsible for the anomalous thermal stiffening. The effect was further localized to the motions of the FeII site within the orthorhombic structure, which participates disproportionately in the anomalous phonon stiffening.

An Analysis of the Beaufort Sea Thermohaline Structure and Variability, and Its Effects on Acoustic Propagation

DTIC Science & Technology

2016-06-01

BEAUFORT SEA THERMOHALINE STRUCTURE AND VARIABILITY, AND ITS EFFECTS ON ACOUSTIC PROPAGATION by Annalise N. Pearson June 2016 Thesis...STRUCTURE AND VARIABILITY, AND ITS EFFECTS ON ACOUSTIC PROPAGATION 5. FUNDING NUMBERS 6. AUTHOR(S) Annalise N. Pearson 7. PERFORMING ORGANIZATION...public release; distribution is unlimited AN ANALYSIS OF THE BEAUFORT SEA THERMOHALINE STRUCTURE AND VARIABILITY, AND ITS EFFECTS ON ACOUSTIC

Analysis of passive acoustic ranging of helicopters from the joint acoustic propagation experiment

NASA Technical Reports Server (NTRS)

Carnes, Benny L.; Morgan, John C.

1993-01-01

For more than twenty years, personnel of the U.S.A.E. Waterways Experiment Station (WES) have been performing research dealing with the application of sensors for detection of military targets. The WES research has included the use of seismic, acoustic, magnetic, and other sensors to detect, track, and classify military ground targets. Most of the WES research has been oriented toward the employment of such sensors in a passive mode. Techniques for passive detection are of particular interest in the Army because of the advantages over active detection. Passive detection methods are not susceptible to interception, detection, jamming, or location of the source by the threat. A decided advantage for using acoustic and seismic sensors for detection in tactical situations is the non-line-of-sight capability; i.e., detection of low flying helicopters at long distances without visual contact. This study was conducted to analyze the passive acoustic ranging (PAR) concept using a more extensive data set from the Joint Acoustic Propagation Experiment (JAPE).

Nonbolometric bottleneck in electron-phonon relaxation in ultrathin WSi films

NASA Astrophysics Data System (ADS)

Sidorova, Mariia V.; Kozorezov, A. G.; Semenov, A. V.; Korneeva, Yu. P.; Mikhailov, M. Yu.; Devizenko, A. Yu.; Korneev, A. A.; Chulkova, G. M.; Goltsman, G. N.

2018-05-01

We developed the model of the internal phonon bottleneck to describe the energy exchange between the acoustically soft ultrathin metal film and acoustically rigid substrate. Discriminating phonons in the film into two groups, escaping and nonescaping, we show that electrons and nonescaping phonons may form a unified subsystem, which is cooled down only due to interactions with escaping phonons, either due to direct phonon conversion or indirect sequential interaction with an electronic system. Using an amplitude-modulated absorption of the sub-THz radiation technique, we studied electron-phonon relaxation in ultrathin disordered films of tungsten silicide. We found an experimental proof of the internal phonon bottleneck. The experiment and simulation based on the proposed model agree well, resulting in τe -ph˜14 0 -19 0 ps at TC=3.4 K , supporting the results of earlier measurements by independent techniques.

Acoustical phonon anomaly in the Raman spectra of intermediate valent TmSe 1-xTe x and Tm xSe

NASA Astrophysics Data System (ADS)

Treindl, A.; Wachter, P.

1980-12-01

In the Raman spectra of intermediate valent TmSe 1- xTe x the same anomaly within the acoustical phonon band at 60 cm -1 is found as in Tm xSe. The connection of this anomaly with the valence mixing is confirmed. In a one-dimensional model calculation it is shown that a renormalized LA dispersion curve can produce the observed anomalous peak in the phonon DOS. As an alternative interpretation the possibility of a low energy electronic excitation at 60 cm -1 is discussed.

Effects of counterion valency on the damping of phonons propagating along the axial direction of liquid-crystalline DNA

NASA Astrophysics Data System (ADS)

Liu, Yun; Chen, Sow-Hsin; Berti, Debora; Baglioni, Piero; Alatas, Ahmet; Sinn, Harald; Alp, Ercan; Said, Ayman

2005-12-01

The phonon propagation and damping along the axial direction of films of aligned 40wt% calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S (Q,E) as a function of transferred energy E =ℏω, and the magnitude of the transferred wave vector Q. S (Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30nm-1. A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q =4nm-1. The high-frequency sound speed obtained in this Q range is 3100m /s, which is about twice faster than the ultrasound speed of 1800m/s, measured by Brillouin light scattering at Q ˜0.01nm-1 at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between ˜12.5 and ˜22.5nm-1 are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4ps.

Sound and heat revolutions in phononics

NASA Astrophysics Data System (ADS)

Maldovan, Martin

2013-11-01

The phonon is the physical particle representing mechanical vibration and is responsible for the transmission of everyday sound and heat. Understanding and controlling the phononic properties of materials provides opportunities to thermally insulate buildings, reduce environmental noise, transform waste heat into electricity and develop earthquake protection. Here I review recent progress and the development of new ideas and devices that make use of phononic properties to control both sound and heat. Advances in sonic and thermal diodes, optomechanical crystals, acoustic and thermal cloaking, hypersonic phononic crystals, thermoelectrics, and thermocrystals herald the next technological revolution in phononics.

Evaluation of Acoustic Propagation Paths into the Human Head

DTIC Science & Technology

2005-07-25

paths. A 3D finite-element solid mesh was constructed using a digital image database of an adult male head. Finite-element analysis was used to model the...air-borne sound pressure amplitude) via the alternate propagation paths. A 3D finite-element solid mesh was constructed using a digital image database ... database of an adult male head Coupled acoustic-mechanical finite-element analysis (FEA) was used to model the wave propagation through the fluid-solid

Preface: Phonons 2007

NASA Astrophysics Data System (ADS)

Perrin, Bernard

2007-06-01

The conference PHONONS 2007 was held 15-20 July 2007 in the Conservatoire National des Arts et Métiers (CNAM) Paris, France. CNAM is a college of higher technology for training students in the application of science to industry, founded by Henri Grégoire in 1794. This was the 12th International Conference on Phonon Scattering in Condensed Matter. This international conference series, held every 3 years, started in France at Sainte-Maxime in 1972. It was then followed by meetings at Nottingham (1975), Providence (1979), Stuttgart (1983), Urbana-Champaign (1986), Heidelberg (1989), Ithaca (1992), Sapporo (1995), Lancaster (1998), Dartmouth (2001) and St Petersburg (2004). PHONONS 2007 was attended by 346 delegates from 37 different countries as follows: France 120, Japan 45, Germany 25, USA 25, Russia 21, Italy 13, Poland 9, UK 9, Canada 7, The Netherlands 7, Finland 6, Spain 6, Taiwan 6, Greece 4, India 4, Israel 4, Ukraine 4, Serbia 3, South Africa 3, Argentina 2, Belgium 2, China 2, Iran 2, Korea 2, Romania 2, Switzerland 2, and one each from Belarus, Bosnia-Herzegovina, Brazil, Bulgaria, Egypt, Estonia, Mexico, Moldova, Morocco, Saudi Arabia, Turkey. There were 5 plenary lectures, 14 invited talks and 84 oral contributions; 225 posters were presented during three poster sessions. The first plenary lecture was given by H J Maris who presented fascinating movies featuring the motion of a single electron in liquid helium. Robert Blick gave us a review on the new possibilities afforded by nanotechnology to design nano-electomechanical systems (NEMS) and the way to use them to study elementary and fundamental processes. The growing interest for phonon transport studies in nanostructured materials was demonstrated by Arun Majumdar. Andrey Akimov described how ultrafast acoustic solitons can monitor the optical properties of quantum wells. Finally, Maurice Chapellier told us how

On the interplay between phonon-boundary scattering and phonon-point-defect scattering in SiGe thin films

NASA Astrophysics Data System (ADS)

Iskandar, A.; Abou-Khalil, A.; Kazan, M.; Kassem, W.; Volz, S.

2015-03-01

This paper provides theoretical understanding of the interplay between the scattering of phonons by the boundaries and point-defects in SiGe thin films. It also provides a tool for the design of SiGe-based high-efficiency thermoelectric devices. The contributions of the alloy composition, grain size, and film thickness to the phonon scattering rate are described by a model for the thermal conductivity based on the single-mode relaxation time approximation. The exact Boltzmann equation including spatial dependence of phonon distribution function is solved to yield an expression for the rate at which phonons scatter by the thin film boundaries in the presence of the other phonon scattering mechanisms. The rates at which phonons scatter via normal and resistive three-phonon processes are calculated by using perturbation theories with taking into account dispersion of confined acoustic phonons in a two dimensional structure. The vibrational parameters of the model are deduced from the dispersion of confined acoustic phonons as functions of temperature and crystallographic direction. The accuracy of the model is demonstrated with reference to recent experimental investigations regarding the thermal conductivity of single-crystal and polycrystalline SiGe films. The paper describes the strength of each of the phonon scattering mechanisms in the full temperature range. Furthermore, it predicts the alloy composition and film thickness that lead to minimum thermal conductivity in a single-crystal SiGe film, and the alloy composition and grain size that lead to minimum thermal conductivity in a polycrystalline SiGe film.

Acoustic/seismic signal propagation and sensor performance modeling

NASA Astrophysics Data System (ADS)

Wilson, D. Keith; Marlin, David H.; Mackay, Sean

2007-04-01

Performance, optimal employment, and interpretation of data from acoustic and seismic sensors depend strongly and in complex ways on the environment in which they operate. Software tools for guiding non-expert users of acoustic and seismic sensors are therefore much needed. However, such tools require that many individual components be constructed and correctly connected together. These components include the source signature and directionality, representation of the atmospheric and terrain environment, calculation of the signal propagation, characterization of the sensor response, and mimicking of the data processing at the sensor. Selection of an appropriate signal propagation model is particularly important, as there are significant trade-offs between output fidelity and computation speed. Attenuation of signal energy, random fading, and (for array systems) variations in wavefront angle-of-arrival should all be considered. Characterization of the complex operational environment is often the weak link in sensor modeling: important issues for acoustic and seismic modeling activities include the temporal/spatial resolution of the atmospheric data, knowledge of the surface and subsurface terrain properties, and representation of ambient background noise and vibrations. Design of software tools that address these challenges is illustrated with two examples: a detailed target-to-sensor calculation application called the Sensor Performance Evaluator for Battlefield Environments (SPEBE) and a GIS-embedded approach called Battlefield Terrain Reasoning and Awareness (BTRA).

Phonons and their dispersion in model ferroelastics Hg2Hal2

NASA Astrophysics Data System (ADS)

Roginskii, E. M.; Kvasov, A. A.; Markov, Yu. F.; Smirnov, M. B.

2012-05-01

Dispersion relations of the acoustic and optical phonon frequencies have been calculated and plotted, and the density of states of the phonon spectrum of Hg2Cl2 and Hg2Br2 crystals has been derived. The effect of hydrostatic pressure on the frequencies of acoustic and optical phonons and their dispersion has been theoretically analyzed. It has been found that an increase in the pressure leads to a strong softening of the slowest acoustic TA branch (the soft mode) at the X point of the Brillouin zone boundary, which is consistent with the phenomenological Landau theory and correlates with experiment.

Corrigendum and addendum. Modeling weakly nonlinear acoustic wave propagation

DOE PAGES

Christov, Ivan; Christov, C. I.; Jordan, P. M.

2014-12-18

This article presents errors, corrections, and additions to the research outlined in the following citation: Christov, I., Christov, C. I., & Jordan, P. M. (2007). Modeling weakly nonlinear acoustic wave propagation. The Quarterly Journal of Mechanics and Applied Mathematics, 60(4), 473-495.

Tunable broadband unidirectional acoustic transmission based on a waveguide with phononic crystal

NASA Astrophysics Data System (ADS)

Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Wan, Lele

2016-08-01

In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

Propagation of acoustic-gravity waves in arctic zones with elastic ice-sheets

NASA Astrophysics Data System (ADS)

Kadri, Usama; Abdolali, Ali; Kirby, James T.

2017-04-01

We present an analytical solution of the boundary value problem of propagating acoustic-gravity waves generated in the ocean by earthquakes or ice-quakes in arctic zones. At the surface, we assume elastic ice-sheets of a variable thickness, and show that the propagating acoustic-gravity modes have different mode shape than originally derived by Ref. [1] for a rigid ice-sheet settings. Computationally, we couple the ice-sheet problem with the free surface model by Ref. [2] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice-sheets cause inter modal transition at the edges and multidirectional reflections. We then derive a depth-integrated equation valid for spatially slowly varying thickness of ice-sheet and water depth. Surprisingly, and unlike the free-surface setting, here it is found that the higher acoustic-gravity modes exhibit a larger contribution. These modes travel at the speed of sound in water carrying information on their source, e.g. ice-sheet motion or submarine earthquake, providing various implications for ocean monitoring and detection of quakes. In addition, we found that the propagating acoustic-gravity modes can result in orbital displacements of fluid parcels sufficiently high that may contribute to deep ocean currents and circulation, as postulated by Refs. [1, 3]. References [1] U. Kadri, 2016. Generation of Hydroacoustic Waves by an Oscillating Ice Block in Arctic Zones. Advances in Acoustics and Vibration, 2016, Article ID 8076108, 7 pages http://dx.doi.org/10.1155/2016/8076108 [2] A. Abdolali, J. T. Kirby and G. Bellotti, 2015, Depth-integrated equation for hydro-acoustic waves with bottom damping, J. Fluid Mech., 766, R1 doi:10.1017/jfm.2015.37 [3] U. Kadri, 2014. Deep ocean water transportation by acoustic?gravity waves. J. Geophys. Res. Oceans, 119, doi:10.1002/ 2014JC010234

Superconducting Qubit (transmon) coupled to Surface Acoustic Waves (SAWs)

NASA Astrophysics Data System (ADS)

Guo, Lingzhen; Johansson, Göran

We work on a hybrid system, which couples the transmon in circuit QED to the propagating mechanical modes of Surface Acoustic Waves (SAWs). This is an analogue of circuit QED system but replacing the microwave photons by SAW phonons. We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. We show that the giant atom can generate entangled phonon pairs, which may have applications in quantum communication. L.G. acknowledges financial support from Carl-Zeiss Stiftung (0563-2.8/508/2).

Bottom Interaction in Long Range Acoustic Propagation

DTIC Science & Technology

2006-09-30

Pacific Ocean utilizing controlled sources and vertical and horizontal receiver arrays . Broadband sources are considered with typical center...The LOAPEX (Long-range Ocean Acoustic Propagation Experiment) vertical line arrays (VLA) are described on page 1 of the LOAPEX cruise report: " The...hydrophone arrays on the two combined VLAs covered most of the 5-km water column. We refer to one of the VLAs as the deep VLA (DVLA), located at

Electron-phonon coupling and phonon subbands in small, electrically heated metal wires

NASA Astrophysics Data System (ADS)

Perrin, N.; Wybourne, M. N.

1996-02-01

The initial work of Perrin and Budd is extended to small metal wires in which the usual bulk phonon spectrum is modified into a series of acoustic subbands at low temperature. We analyze the contribution of the subbands to the lack of equilibrium between the electrons and the phonons in the wire heated by an applied electric field. The resulting electrical behavior of the wire is also considered and compared to experimental results.

Enhancement of phonon backscattering due to confinement of ballistic phonon pathways in silicon as studied with a microfabricated phonon spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otelaja, O. O.; Robinson, R. D., E-mail: rdr82@cornell.edu

2015-10-26

In this work, the mechanism for enhanced phonon backscattering in silicon is investigated. An understanding of phonon propagation through substrates has implications for engineering heat flow at the nanoscale, for understanding sources of decoherence in quantum systems, and for realizing efficient phonon-mediated particle detectors. In these systems, phonons that backscatter from the bottom of substrates, within the crystal or from interfaces, often contribute to the overall detector signal. We utilize a microscale phonon spectrometer, comprising superconducting tunnel junction emitters and detectors, to specifically probe phonon backscattering in silicon substrates (∼500 μm thick). By etching phonon “enhancers” or deep trenches (∼90 μm) aroundmore » the detectors, we show that the backscattered signal level increases by a factor of ∼2 for two enhancers versus one enhancer. Using a geometric analysis of the phonon pathways, we show that the mechanism of the backscattered phonon enhancement is due to confinement of the ballistic phonon pathways and increased scattering off the enhancer walls. Our result is applicable to the geometric design and patterning of substrates that are employed in phonon-mediated detection devices.« less

Phonon anomalies in FeS

DOE PAGES

Baum, A.; Milosavljevic, A.; Lazarevic, N.; ...

2018-02-12

Here, we present results from light scattering experiments on tetragonal FeS with the focus placed on lattice dynamics. We identify the Raman active A 1g and B 1g phonon modes, a second order scattering process involving two acoustic phonons, and contributions from potentially defect-induced scattering. The temperature dependence between 300 and 20 K of all observed phonon energies is governed by the lattice contraction. Below 20 K the phonon energies increase by 0.5–1 cm -1 , thus indicating putative short range magnetic order. Additionally, along with the experiments we performed lattice-dynamical simulations and a symmetry analysis for the phonons andmore » potential overtones and find good agreement with the experiments. In particular, we argue that the two-phonon excitation observed in a gap between the optical branches becomes observable due to significant electron-phonon interaction.« less

Phonon anomalies in FeS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baum, A.; Milosavljevic, A.; Lazarevic, N.

Here, we present results from light scattering experiments on tetragonal FeS with the focus placed on lattice dynamics. We identify the Raman active A 1g and B 1g phonon modes, a second order scattering process involving two acoustic phonons, and contributions from potentially defect-induced scattering. The temperature dependence between 300 and 20 K of all observed phonon energies is governed by the lattice contraction. Below 20 K the phonon energies increase by 0.5–1 cm -1 , thus indicating putative short range magnetic order. Additionally, along with the experiments we performed lattice-dynamical simulations and a symmetry analysis for the phonons andmore » potential overtones and find good agreement with the experiments. In particular, we argue that the two-phonon excitation observed in a gap between the optical branches becomes observable due to significant electron-phonon interaction.« less

Coherent Manipulation of Phonons at the Nanoscale

NASA Astrophysics Data System (ADS)

Yu, Shangjie; Ouyang, Min

Phonons play a key role in almost every physical process, including for example dephasing phenomena of electronic quantum states, electric and heat transports. Therefore, understanding and even manipulating phonons represent a pre-requisite for tailoring phonons-mediated physical processes. In this talk, we will first present how to employ ultrafast optical spectroscopy to probe acoustic phonon modes in colloidal metallic nanoparticles. Furthermore, we have developed various phonon manipulation schemes that can be achieved by a train of optical pulses in time domain to allow selective control of phonon modes. Our theoretical modeling and simulation demonstrates an excellent agreement with experimental results, thus providing a future guideline on more complex phononic control at the nanoscale.

Optical and acoustic sensing using Fano-like resonances in dual phononic and photonic crystal plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amoudache, Samira; Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri, B.P. 17 RP, 15000 Tizi-Ouzou; Moiseyenko, Rayisa

2016-03-21

We perform a theoretical study based on the transmissions of optical and acoustic waves normally impinging to a periodic perforated silicon plate when the embedded medium is a liquid and show the existence of Fano-like resonances in both cases. The signature of the resonances appears as well-defined asymmetric peaks in the phononic and photonic transmission spectra. We show that the origin of the Fano-like resonances is different with respect to the nature of the wave. In photonic, the origin comes from guided modes in the photonic plate while in phononic we show that it comes from the excitation of standingmore » waves confined inside the cavity coming from the deformation of the water/silicon edges of the cylindrical inclusion. We finally use these features for sensing and show ultra-sensitivity to the light and sound velocities for different concentrations of analytes.« less

Acoustic phonon dephasing in shallow GaAs/Ga 1- xAl xAs single quantum wells

NASA Astrophysics Data System (ADS)

Cassabois, G.; Meccherini, S.; Roussignol, Ph.; Bogani, F.; Gurioli, M.; Colocci, M.; Planel, R.; Thierry-Mieg, V.

1998-07-01

The intermediate dimensionality regime is studied on a set of shallow GaAs/Ga 1- xAl xAs single quantum wells. Such heterostructures exhibit 2D strong excitonic electroabsorption together with near 3D fast transport properties. We report dephasing time measurements ( T2) of the heavy-hole exciton and we show that the acoustic phonon contribution decreases with x to a value in good agreement with theoretical predictions for GaAs bulk.

Controlled exciton transfer between quantum dots with acoustic phonons taken into account

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golovinski, P. A., E-mail: golovinski@bk.ru

2015-09-15

A system of excitons in two quantum dots coupled by the dipole–dipole interaction is investigated. The excitation transfer process controlled by the optical Stark effect at nonresonant frequencies is considered and the effect of the interaction between excitons and acoustic phonons in a medium on this process is taken into account. The system evolution is described using quantum Heisenberg equations. A truncated set of equations is obtained and the transfer dynamics is numerically simulated. High-efficiency picosecond switching of the excitation transfer by a laser pulse with a rectangular envelope is demonstrated. The dependence of picosecond switching on the quantum-dot parametersmore » and optical-pulse length is presented.« less

First-principles prediction of phononic thermal conductivity of silicene: A comparison with graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Xiaokun; Yang, Ronggui, E-mail: Ronggui.Yang@Colorado.Edu

2015-01-14

There has been great interest in two-dimensional materials, beyond graphene, for both fundamental sciences and technological applications. Silicene, a silicon counterpart of graphene, has been shown to possess some better electronic properties than graphene. However, its thermal transport properties have not been fully studied. In this paper, we apply the first-principles-based phonon Boltzmann transport equation to investigate the thermal conductivity of silicene as well as the phonon scattering mechanisms. Although both graphene and silicene are two-dimensional crystals with similar crystal structure, we find that phonon transport in silicene is quite different from that in graphene. The thermal conductivity of silicenemore » shows a logarithmic increase with respect to the sample size due to the small scattering rates of acoustic in-plane phonon modes, while that of graphene is finite. Detailed analysis of phonon scattering channels shows that the linear dispersion of the acoustic out-of-plane (ZA) phonon modes, which is induced by the buckled structure, makes the long-wavelength longitudinal acoustic phonon modes in silicene not as efficiently scattered as that in graphene. Compared with graphene, where most of the heat is carried by the acoustic out-of-plane (ZA) phonon modes, the ZA phonon modes in silicene only have ∼10% contribution to the total thermal conductivity, which can also be attributed to the buckled structure. This systematic comparison of phonon transport and thermal conductivity of silicene and graphene using the first-principle-based calculations shed some light on other two-dimensional materials, such as two-dimensional transition metal dichalcogenides.« less

Experimental Study of Electron and Phonon Dynamics in Nanoscale Materials by Ultrafast Laser Time-Domain Spectroscopy

NASA Astrophysics Data System (ADS)

Shen, Xiaohan

With the rapid advances in the development of nanotechnology, nowadays, the sizes of elementary unit, i.e. transistor, of micro- and nanoelectronic devices are well deep into nanoscale. For the pursuit of cheaper and faster nanoscale electronic devices, the size of transistors keeps scaling down. As the miniaturization of the nanoelectronic devices, the electrical resistivity increases dramatically, resulting rapid growth in the heat generation. The heat generation and limited thermal dissipation in nanoscale materials have become a critical problem in the development of the next generation nanoelectronic devices. Copper (Cu) is widely used conducting material in nanoelectronic devices, and the electron-phonon scattering is the dominant contributor to the resistivity in Cu nanowires at room temperature. Meanwhile, phonons are the main carriers of heat in insulators, intrinsic and lightly doped semiconductors. The thermal transport is an ensemble of phonon transport, which strongly depends on the phonon frequency. In addition, the phonon transport in nanoscale materials can behave fundamentally different than in bulk materials, because of the spatial confinement. However, the size effect on electron-phonon scattering and frequency dependent phonon transport in nanoscale materials remain largely unexplored, due to the lack of suitable experimental techniques. This thesis is mainly focusing on the study of carrier dynamics and acoustic phonon transport in nanoscale materials. The weak photothermal interaction in Cu makes thermoreflectance measurement difficult, we rather measured the reflectivity change of Cu induced by absorption variation. We have developed a method to separately measure the processes of electron-electron scattering and electron-phonon scattering in epitaxial Cu films by monitoring the transient reflectivity signal using the resonant probe with particular wavelengths. The enhancement on electron-phonon scattering in epitaxial Cu films with thickness

Phonon-assisted oscillatory exciton dynamics in monolayer MoSe 2

DOE PAGES

Chow, Colin M.; Yu, Hongyi; Jones, Aaron M.; ...

2017-10-13

In monolayer semiconductor transition metal dichalcogenides, the exciton–phonon interaction strongly affects the photocarrier dynamics. Here, we report on an unusual oscillatory enhancement of the neutral exciton photoluminescence with the excitation laser frequency in monolayer MoSe 2. The frequency of oscillation matches that of the M-point longitudinal acoustic phonon, LA(M), suggesting the significance of zone-edge acoustic phonons and hence the deformation potential in exciton-phonon coupling in MoSe 2. Moreover, oscillatory behavior is observed in the steady-state emission linewidth and in time-resolved PLE data, which reveals variation with excitation energy in the exciton lifetime. These results clearly expose the key role playedmore » by phonons in the exciton formation and relaxation dynamics of two-dimensional van der Waals semiconductors.« less

Phononic properties of superlattices and multi quantum well heterostructures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wagner, Markus R.; Reparaz, Juan Sebastian; Callsen, Gordon; Nippert, Felix; Kure, Thomas; Hoffmann, Axel; Hugues, Maxime; Teysseire, Monique; Damilano, Benjamin; Chauveau, Jean-Michel

2017-03-01

We address the electronic, phononic, and thermal properties of oxide based superlattices and multi quantum well heterostructures. In the first part, we review the present understanding of phonon coupling and phonon propagation in superlattices and elucidate current research aspects of phonon coherence in these structure. Subsequently, we focus on the experimental study of MBE grown ZnO/ZnMgO multi quantum well heterostructures with varying Mg content, barrier thickness, quantum well thickness, and number of periods. In particular, we discuss how the controlled variation of these parameters affect the phonon dispersion relation and phonon propagation and their impact on the thermal properties.

Phononic crystals of spherical particles: A tight binding approach

NASA Astrophysics Data System (ADS)

Mattarelli, M.; Secchi, M.; Montagna, M.

2013-11-01

The vibrational dynamics of a fcc phononic crystal of spheres is studied and compared with that of a single free sphere, modelled either by a continuous homogeneous medium or by a finite cluster of atoms. For weak interaction among the spheres, the vibrational dynamics of the phononic crystal is described by shallow bands, with low degree of dispersion, corresponding to the acoustic spheroidal and torsional modes of the single sphere. The phonon displacements are therefore related to the vibrations of a sphere, as the electron wave functions in a crystal are related to the atomic wave functions in a tight binding model. Important dispersion is found for the two lowest phonon bands, which correspond to zero frequency free translation and rotation of a free sphere. Brillouin scattering spectra are calculated at some values of the exchanged wavevectors of the light, and compared with those of a single sphere. With weak interaction between particles, given the high acoustic impedance mismatch in dry systems, the density of phonon states consist of sharp bands separated by large gaps, which can be well accounted for by a single particle model. Based on the width of the frequency gaps, tunable with the particle size, and on the small number of dispersive acoustic phonons, such systems may provide excellent materials for application as sound or heat filters.

Impacts of short-time scale water column variability on broadband high-frequency acoustic wave propagation

NASA Astrophysics Data System (ADS)

Eickmeier, Justin

Acoustical oceanography is one way to study the ocean, its internal layers, boundaries and all processes occurring within using underwater acoustics. Acoustical sensing techniques allows for the measurement of ocean processes from within that logistically or financially preclude traditional in-situ measurements. Acoustic signals propagate as pressure wavefronts from a source to a receiver through an ocean medium with variable physical parameters. The water column physical parameters that change acoustic wave propagation in the ocean include temperature, salinity, current, surface roughness, seafloor bathymetry, and vertical stratification over variable time scales. The impacts of short-time scale water column variability on acoustic wave propagation include coherent and incoherent surface reflections, wavefront arrival time delay, focusing or defocusing of the intensity of acoustic beams and refraction of acoustic rays. This study focuses on high-frequency broadband acoustic waves, and examines the influence of short-time scale water column variability on broadband high-frequency acoustics, wavefronts, from 7 to 28 kHz, in shallow water. Short-time scale variability is on the order of seconds to hours and the short-spatial scale variability is on the order of few centimeters. Experimental results were collected during an acoustic experiment along 100 m isobaths and data analysis was conducted using available acoustic wave propagation models. Three main topics are studied to show that acoustic waves are viable as a remote sensing tool to measure oceanographic parameters in shallow water. First, coherent surface reflections forming striation patterns, from multipath receptions, through rough surface interaction of broadband acoustic signals with the dynamic sea surface are analyzed. Matched filtered results of received acoustic waves are compared with a ray tracing numerical model using a sea surface boundary generated from measured water wave spectra at the time of

Long-range propagation of plasmon and phonon polaritons in hyperbolic-metamaterial waveguides

NASA Astrophysics Data System (ADS)

Babicheva, Viktoriia E.

2017-12-01

We study photonic multilayer waveguides that include layers of materials and metamaterials with a hyperbolic dispersion (HMM). We consider the long-range propagation of plasmon and phonon polaritons at the dielectric-HMM interface in different waveguide geometries (single boundary or different layers of symmetric cladding). In contrast to the traditional analysis of geometrical parameters, we make an emphasis on the optical properties of constituent materials: solving dispersion equations, we analyze how dielectric and HMM permittivities affect propagation length and mode size of waveguide eigenmodes. We derive figures of merit that should be used for each waveguide in a broad range of permittivity values as well as compare them with plasmonic waveguides. We show that the conventional plasmonic quality factor, which is the ratio of real to imaginary parts of permittivity, is not applicable to the case of waveguides with complex structure. Both telecommunication wavelengths and mid-infrared spectral ranges are of interest considering recent advances in van der Waals materials, such as hexagonal boron nitride. We evaluate the performance of the waveguides with hexagonal boron nitride in the range where it possesses hyperbolic dispersion (wavelength 6.3-7.3 μm), and we show that these waveguides with natural hyperbolic properties have higher propagation lengths than metal-based HMM waveguides.

Splash, pop, sizzle: Information processing with phononic computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sklan, Sophia R.

2015-05-15

Phonons, the quanta of mechanical vibration, are important to the transport of heat and sound in solid materials. Recent advances in the fundamental control of phonons (phononics) have brought into prominence the potential role of phonons in information processing. In this review, the many directions of realizing phononic computing and information processing are examined. Given the relative similarity of vibrational transport at different length scales, the related fields of acoustic, phononic, and thermal information processing are all included, as are quantum and classical computer implementations. Connections are made between the fundamental questions in phonon transport and phononic control and themore » device level approach to diodes, transistors, memory, and logic. .« less

Visualization of stress wave propagation via air-coupled acoustic emission sensors

NASA Astrophysics Data System (ADS)

Rivey, Joshua C.; Lee, Gil-Yong; Yang, Jinkyu; Kim, Youngkey; Kim, Sungchan

2017-02-01

We experimentally demonstrate the feasibility of visualizing stress waves propagating in plates using air-coupled acoustic emission sensors. Specifically, we employ a device that embeds arrays of microphones around an optical lens in a helical pattern. By implementing a beamforming technique, this remote sensing system allows us to record wave propagation events in situ via a single-shot and full-field measurement. This is a significant improvement over the conventional wave propagation tracking approaches based on laser doppler vibrometry or digital image correlation techniques. In this paper, we focus on demonstrating the feasibility and efficacy of this air-coupled acoustic emission technique by using large metallic plates exposed to external impacts. The visualization results of stress wave propagation will be shown under various impact scenarios. The proposed technique can be used to characterize and localize damage by detecting the attenuation, reflection, and scattering of stress waves that occurs at damage locations. This can ultimately lead to the development of new structural health monitoring and nondestructive evaluation methods for identifying hidden cracks or delaminations in metallic or composite plate structures, simultaneously negating the need for mounted contact sensors.

Acoustic wave propagation in bubbly flow with gas, vapor or their mixtures.

PubMed

Zhang, Yuning; Guo, Zhongyu; Gao, Yuhang; Du, Xiaoze

2018-01-01

Presence of bubbles in liquids could significantly alter the acoustic waves in terms of wave speed and attenuation. In the present paper, acoustic wave propagation in bubbly flows with gas, vapor and gas/vapor mixtures is theoretically investigated in a wide range of parameters (including frequency, bubble radius, void fraction, and vapor mass fraction). Our finding reveals two types of wave propagation behavior depending on the vapor mass fraction. Furthermore, the minimum wave speed (required for the closure of cavitation modelling in the sonochemical reactor design) is analyzed and the influences of paramount parameters on it are quantitatively discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Low order models for uncertainty quantification in acoustic propagation problems

NASA Astrophysics Data System (ADS)

Millet, Christophe

2016-11-01

Long-range sound propagation problems are characterized by both a large number of length scales and a large number of normal modes. In the atmosphere, these modes are confined within waveguides causing the sound to propagate through multiple paths to the receiver. For uncertain atmospheres, the modes are described as random variables. Concise mathematical models and analysis reveal fundamental limitations in classical projection techniques due to different manifestations of the fact that modes that carry small variance can have important effects on the large variance modes. In the present study, we propose a systematic strategy for obtaining statistically accurate low order models. The normal modes are sorted in decreasing Sobol indices using asymptotic expansions, and the relevant modes are extracted using a modified iterative Krylov-based method. The statistics of acoustic signals are computed by decomposing the original pulse into a truncated sum of modal pulses that can be described by a stationary phase method. As the low-order acoustic model preserves the overall structure of waveforms under perturbations of the atmosphere, it can be applied to uncertainty quantification. The result of this study is a new algorithm which applies on the entire phase space of acoustic fields.

Quantum many-body correlations in collective phonon-excitations

NASA Astrophysics Data System (ADS)

Droenner, Leon; Kabuss, Julia; Carmele, Alexander

2018-02-01

We present a theoretical study of a many-emitter phonon laser based on optically driven semiconductor quantum dots placed within an acoustic nanocavity. A transformation of the phonon laser Hamiltonian leads to a Tavis-Cummings type interaction with an unexpected additional many-emitter energy shift. This many-emitter interaction with the cavity mode results in a variety of phonon resonances which dependent strongly on the number of participating emitters. These collective resonances show the highest phonon output. Furthermore, we show that the output can be increased even more via lasing at the two phonon resonance.

Genetic Algorithm Optimization of Phononic Bandgap Structures

DTIC Science & Technology

2006-09-01

a GA with a computational finite element method for solving the acoustic wave equation, and find optimal designs for both metal-matrix composite...systems consisting of Ti/SiC, and H2O-filled porous ceramic media, by maximizing the relative acoustic bandgap for these media. The term acoustic here...stress minimization, global optimization, phonon bandgap, genetic algorithm, periodic elastic media, inhomogeneity, inclusion, porous media, acoustic

Study of phonons in irradiated epitaxial thin films of UO2

NASA Astrophysics Data System (ADS)

Rennie, S.; Lawrence Bright, E.; Darnbrough, J. E.; Paolasini, L.; Bosak, A.; Smith, A. D.; Mason, N.; Lander, G. H.; Springell, R.

2018-06-01

We report experiments to determine the effect of radiation damage on the phonon spectra of the most common nuclear fuel, UO2. We irradiated thin (˜300 nm) epitaxial films of UO2 with 2.1 MeV He2 + ions to 0.15 displacements per atom and a lattice swelling of Δ a /a ˜0.6 % and then used grazing-incidence inelastic x-ray scattering to measure the phonon spectrum. We succeeded in observing the acoustic modes, both transverse and longitudinal, across the Brillouin zone. The phonon energies, in both the pristine and irradiated samples, are unchanged from those observed in bulk material. On the other hand, the phonon linewidths (inversely proportional to the phonon lifetimes) show a significant broadening when comparing the pristine and irradiated samples. This effect is shown to increase with phonon energy across the Brillouin zone. The decreases in the phonon lifetimes of the acoustic modes are roughly consistent with a 50% reduction in the thermal conductivity.

Investigation of phononic crystals for dispersive surface acoustic wave ozone sensors

NASA Astrophysics Data System (ADS)

Westafer, Ryan S.

The object of this research was to investigate dispersion in surface phononic crystals (PnCs) for application to a newly developed passive surface acoustic wave (SAW) ozone sensor. Frequency band gaps and slow sound already have been reported for PnC lattice structures. Such engineered structures are often advertised to reduce loss, increase sensitivity, and reduce device size. However, these advances have not yet been realized in the context of surface acoustic wave sensors. In early work, we computed SAW dispersion in patterned surface structures and we confirmed that our finite element computations of SAW dispersion in thin films and in one dimensional surface PnC structures agree with experimental results obtained by laser probe techniques. We analyzed the computations to guide device design in terms of sensitivity and joint spectral operating point. Next we conducted simulations and experiments to determine sensitivity and limit of detection for more conventional dispersive SAW devices and PnC sensors. Finally, we conducted extensive ozone detection trials on passive reflection mode SAW devices, using distinct components of the time dispersed response to compensate for the effect of temperature. The experimental work revealed that the devices may be used for dosimetry applications over periods of several days.

Excitation of surface waves on one-dimensional solid–fluid phononic crystals and the beam displacement effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moiseyenko, Rayisa P.; Georgia Institute of Technology, UMI Georgia Tech – CNRS, George W. Woodruff School of Mechanical Engineering, Georgia Tech Lorraine, 2 rue Marconi, 57070 Metz-Technopole; Liu, Jingfei

The possibility of surface wave generation by diffraction of pressure waves on deeply corrugated one-dimensional phononic crystal gratings is studied both theoretically and experimentally. Generation of leaky surface waves, indeed, is generally invoked in the explanation of the beam displacement effect that can be observed upon reflection on a shallow grating of an acoustic beam of finite width. True surface waves of the grating, however, have a dispersion that lies below the sound cone in water. They thus cannot satisfy the phase-matching condition for diffraction from plane waves of infinite extent incident from water. Diffraction measurements indicate that deeply corrugatedmore » one-dimensional phononic crystal gratings defined in a silicon wafer are very efficient diffraction gratings. They also confirm that all propagating waves detected in water follow the grating law. Numerical simulations however reveal that in the sub-diffraction regime, acoustic energy of a beam of finite extent can be transferred to elastic waves guided at the surface of the grating. Their leakage to the specular direction along the grating surface explains the apparent beam displacement effect.« less

Viscoelastic effect on acoustic band gaps in polymer-fluid composites

NASA Astrophysics Data System (ADS)

Merheb, B.; Deymier, P. A.; Muralidharan, K.; Bucay, J.; Jain, M.; Aloshyna-Lesuffleur, M.; Greger, R. W.; Mohanty, S.; Berker, A.

2009-10-01

In this paper, we present a theoretical analysis of the propagation of acoustic waves through elastic and viscoelastic two-dimensional phononic crystal structures. Numerical calculations of transmission spectra are conducted by extending the finite-difference-time-domain method to account for linear viscoelastic materials with time-dependent moduli. We study a phononic crystal constituted of a square array of cylindrical air inclusions in a solid viscoelastic matrix. The elastic properties of the solid are those of a silicone rubber. This system exhibits very wide band gaps in its transmission spectrum that extend to frequencies in the audible range of the spectrum. These gaps are characteristic of fluid matrix/air inclusion systems and result from the very large contrast between the longitudinal and transverse speeds of sound in rubber. By treating the matrix as a viscoelastic medium within the standard linear solid (SLS) model, we demonstrate that viscoelasticity impacts the transmission properties of the rubber/air phononic crystal not only by attenuating the transmitted acoustic waves but also by shifting the passing bands frequencies toward lower values. The ranges of frequencies exhibiting attenuation or frequency shift are determined by the value of the relaxation time in the SLS model. We show that viscoelasticity can be used to decrease the frequency of pass bands (and consequently stop bands) in viscoelastic/air phononic crystals.

Quantum transport properties of carbon nanotube field-effect transistors with electron-phonon coupling

NASA Astrophysics Data System (ADS)

Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

2007-11-01

We investigated the electron-phonon coupling effects on the electronic transport properties of metallic (5,5)- and semiconducting (10,0)-carbon nanotube devices. We calculated the conductance and mobility of the carbon nanotubes with micron-order lengths at room temperature, using the time-dependent wave-packet approach based on the Kubo-Greenwood formula within a tight-binding approximation. We investigated the scattering effects of both longitudinal acoustic and optical phonon modes on the transport properties. The electron-optical phonon coupling decreases the conductance around the Fermi energy for the metallic carbon nanotubes, while the conductance of semiconductor nanotubes is decreased around the band edges by the acoustic phonons. Furthermore, we studied the Schottky-barrier effects on the mobility of the semiconducting carbon nanotube field-effect transistors for various gate voltages. We clarified how the electron mobilities of the devices are changed by the acoustic phonon.

Wide-Stopband Aperiodic Phononic Filters

NASA Technical Reports Server (NTRS)

Rostem, Karwan; Chuss, David; Denis, K. L.; Wollack, E. J.

2016-01-01

We demonstrate that a phonon stopband can be synthesized from an aperiodic structure comprising a discrete set of phononic filter stages. Each element of the set has a dispersion relation that defines a complete bandgap when calculated under a Bloch boundary condition. Hence, the effective stopband width in an aperiodic phononic filter (PnF) may readily exceed that of a phononic crystal with a single lattice constant or a coherence scale. With simulations of multi-moded phononic waveguides, we discuss the effects of finite geometry and mode-converting junctions on the phonon transmission in PnFs. The principles described may be utilized to form a wide stopband in acoustic and surface wave media. Relative to the quantum of thermal conductance for a uniform mesoscopic beam, a PnF with a stopband covering 1.6-10.4 GHz is estimated to reduce the thermal conductance by an order of magnitude at 75 mK.

A low order flow/acoustics interaction method for the prediction of sound propagation using 3D adaptive hybrid grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kallinderis, Yannis, E-mail: kallind@otenet.gr; Vitsas, Panagiotis A.; Menounou, Penelope

2012-07-15

A low-order flow/acoustics interaction method for the prediction of sound propagation and diffraction in unsteady subsonic compressible flow using adaptive 3-D hybrid grids is investigated. The total field is decomposed into the flow field described by the Euler equations, and the acoustics part described by the Nonlinear Perturbation Equations. The method is shown capable of predicting monopole sound propagation, while employment of acoustics-guided adapted grid refinement improves the accuracy of capturing the acoustic field. Interaction of sound with solid boundaries is also examined in terms of reflection, and diffraction. Sound propagation through an unsteady flow field is examined using staticmore » and dynamic flow/acoustics coupling demonstrating the importance of the latter.« less

Underwater Wireless Sensor Networks: how do acoustic propagation models impact the performance of higher-level protocols?

PubMed

Llor, Jesús; Malumbres, Manuel P

2012-01-01

Several Medium Access Control (MAC) and routing protocols have been developed in the last years for Underwater Wireless Sensor Networks (UWSNs). One of the main difficulties to compare and validate the performance of different proposals is the lack of a common standard to model the acoustic propagation in the underwater environment. In this paper we analyze the evolution of underwater acoustic prediction models from a simple approach to more detailed and accurate models. Then, different high layer network protocols are tested with different acoustic propagation models in order to determine the influence of environmental parameters on the obtained results. After several experiments, we can conclude that higher-level protocols are sensitive to both: (a) physical layer parameters related to the network scenario and (b) the acoustic propagation model. Conditions like ocean surface activity, scenario location, bathymetry or floor sediment composition, may change the signal propagation behavior. So, when designing network architectures for UWSNs, the role of the physical layer should be seriously taken into account in order to assert that the obtained simulation results will be close to the ones obtained in real network scenarios.

Underwater Wireless Sensor Networks: How Do Acoustic Propagation Models Impact the Performance of Higher-Level Protocols?

PubMed Central

Llor, Jesús; Malumbres, Manuel P.

2012-01-01

Several Medium Access Control (MAC) and routing protocols have been developed in the last years for Underwater Wireless Sensor Networks (UWSNs). One of the main difficulties to compare and validate the performance of different proposals is the lack of a common standard to model the acoustic propagation in the underwater environment. In this paper we analyze the evolution of underwater acoustic prediction models from a simple approach to more detailed and accurate models. Then, different high layer network protocols are tested with different acoustic propagation models in order to determine the influence of environmental parameters on the obtained results. After several experiments, we can conclude that higher-level protocols are sensitive to both: (a) physical layer parameters related to the network scenario and (b) the acoustic propagation model. Conditions like ocean surface activity, scenario location, bathymetry or floor sediment composition, may change the signal propagation behavior. So, when designing network architectures for UWSNs, the role of the physical layer should be seriously taken into account in order to assert that the obtained simulation results will be close to the ones obtained in real network scenarios. PMID:22438712

Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rury, Aaron S., E-mail: arury@usc.edu; Sorenson, Shayne; Dawlaty, Jahan M.

2016-03-14

Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone,more » we find sub-cm{sup −1} oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology.« less

Intermolecular electron transfer from intramolecular excitation and coherent acoustic phonon generation in a hydrogen-bonded charge-transfer solid

NASA Astrophysics Data System (ADS)

Rury, Aaron S.; Sorenson, Shayne; Dawlaty, Jahan M.

2016-03-01

Organic materials that produce coherent lattice phonon excitations in response to external stimuli may provide next generation solutions in a wide range of applications. However, for these materials to lead to functional devices in technology, a full understanding of the possible driving forces of coherent lattice phonon generation must be attained. To facilitate the achievement of this goal, we have undertaken an optical spectroscopic study of an organic charge-transfer material formed from the ubiquitous reduction-oxidation pair hydroquinone and p-benzoquinone. Upon pumping this material, known as quinhydrone, on its intermolecular charge transfer resonance as well as an intramolecular resonance of p-benzoquinone, we find sub-cm-1 oscillations whose dispersion with probe energy resembles that of a coherent acoustic phonon that we argue is coherently excited following changes in the electron density of quinhydrone. Using the dynamical information from these ultrafast pump-probe measurements, we find that the fastest process we can resolve does not change whether we pump quinhydrone at either energy. Electron-phonon coupling from both ultrafast coherent vibrational and steady-state resonance Raman spectroscopies allows us to determine that intramolecular electronic excitation of p-benzoquinone also drives the electron transfer process in quinhydrone. These results demonstrate the wide range of electronic excitations of the parent of molecules found in many functional organic materials that can drive coherent lattice phonon excitations useful for applications in electronics, photonics, and information technology.

Sound propagation in and radiation from acoustically lined flow ducts: A comparison of experiment and theory

NASA Technical Reports Server (NTRS)

Plumblee, H. E., Jr.; Dean, P. D.; Wynne, G. A.; Burrin, R. H.

1973-01-01

The results of an experimental and theoretical study of many of the fundamental details of sound propagation in hard wall and soft wall annular flow ducts are reported. The theory of sound propagation along such ducts and the theory for determining the complex radiation impedance of higher order modes of an annulus are outlined, and methods for generating acoustic duct modes are developed. The results of a detailed measurement program on propagation in rigid wall annular ducts with and without airflow through the duct are presented. Techniques are described for measuring cut-on frequencies, modal phase speed, and radial and annular mode shapes. The effects of flow velocity on cut-on frequencies and phase speed are measured. Comparisons are made with theoretical predictions for all of the effects studies. The two microphone method of impedance is used to measure the effects of flow on acoustic liners. A numerical study of sound propagation in annular ducts with one or both walls acoustically lined is presented.

Inelastic x-ray scattering measurements of phonon dynamics in URu 2Si 2

DOE PAGES

Gardner, D. R.; Bonnoit, C. J.; Chisnell, R.; ...

2016-02-11

In this paper, we study high-resolution inelastic x-ray scattering measurements of the acoustic phonons of URu 2Si 2. At all temperatures, the longitudinal acoustic phonon linewidths are anomalously broad at small wave vectors revealing a previously unknown anharmonicity. The phonon modes do not change significantly upon cooling into the hidden order phase. In addition, our data suggest that the increase in thermal conductivity in the hidden order phase cannot be driven by a change in phonon dispersions or lifetimes. Hence, the phonon contribution to the thermal conductivity is likely much less significant compared to that of the magnetic excitations inmore » the low temperature phase.« less

The multipath propagation effect in gunshot acoustics and its impact on the design of sniper positioning systems

NASA Astrophysics Data System (ADS)

Ramos, António L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

2013-06-01

Counter sniper systems rely on the detection and parameter estimation of the shockwave and the muzzle blast in order to determine the sniper location. In real-world situations, these acoustical signals can be disturbed by natural phenomena like weather and climate conditions, multipath propagation effect, and background noise. While some of these issues have received some attention in recent publications with application to gunshot acoustics, the multipath propagation phenomenon whose effect can not be neglected, specially in urban environments, has not yet been discussed in details in the technical literature in the same context. Propagating sound waves can be reflected at the boundaries in the vicinity of sound sources or receivers, whenever there is a difference in acoustical impedance between the reflective material and the air. Therefore, the received signal can be composed of a direct-path signal plus N scaled delayed copies of that signal. This paper presents a discussion on the multipath propagation effect and its impact on the performance and reliability of sniper positioning systems. In our formulation, propagation models for both the shockwave and the muzzle blast are considered and analyzed. Conclusions following the theoretical analysis of the problem are fully supported by actual gunshots acoustical signatures.

Four-phonon scattering reduces intrinsic thermal conductivity of graphene and the contributions from flexural phonons

NASA Astrophysics Data System (ADS)

Feng, Tianli; Ruan, Xiulin

2018-01-01

We have developed a formalism of the exact solution to linearized phonon Boltzmann transport equation (BTE) for thermal conductivity calculation including three- and four-phonon scattering. We find strikingly high four-phonon scattering rates in single-layer graphene (SLG) based on the optimized Tersoff potential. The reflection symmetry in graphene, which forbids the three-ZA (out-of-plane acoustic) scattering, allows the four-ZA processes ZA +ZA ⇌ZA +ZA and ZA ⇌ZA +ZA + ZA. As a result, the large phonon population of the low-energy ZA branch originated from the quadratic phonon dispersion leads to high four-phonon scattering rates, even much higher than the three-phonon scattering rates at room temperature. These four-phonon processes are dominated by the normal processes, which lead to a failure of the single mode relaxation time approximation. Therefore, we have solved the exact phonon BTE using an iterative scheme and then calculated the length- and temperature-dependent thermal conductivities. We find that the predicted thermal conductivity of SLG is lower than the previously predicted value from the three-phonon scattering only. The relative contribution of the ZA branch is reduced from 70% to 30% when four-phonon scattering is included. Furthermore, we have demonstrated that the four-phonon scattering in multilayer graphene and graphite is not strong due to the ZA splitting by interlayer van der Waals interaction. We also demonstrate that the five-phonon process in SLG is not strong due to the restriction of reflection symmetry.

Acoustic propagation in a thermally stratified atmosphere

NASA Technical Reports Server (NTRS)

Vanmoorhem, W. K.

1988-01-01

Acoustic propagation in an atmosphere with a specific form of a temperature profile has been investigated by analytical means. The temperature profile used is representative of an actual atmospheric profile and contains three free parameters. Both lapse and inversion cases have been considered. Although ray solutions have been considered, the primary emphasis has been on solutions of the acoustic wave equation with point source where the sound speed varies with height above the ground corresponding to the assumed temperature profile. The method used to obtain the solution of the wave equation is based on Hankel transformation of the wave equation, approximate solution of the transformed equation for wavelength small compared to the scale of the temperature (or sound speed) profile, and approximate or numerical inversion of the Hankel transformed solution. The solution displays the characteristics found in experimental data but extensive comparison between the models and experimental data has not been carried out.

Acoustic propagation in a thermally stratified atmosphere

NASA Technical Reports Server (NTRS)

Vanmoorhem, W. K.

1987-01-01

Acoustic propagation in an atmosphere with a specific form of temperature profile has been investigated by analytical means. The temperature profile used is representative of an actual atmospheric profile and contains three free parameters. Both lapse and inversion cases have been considered. Although ray solution have been considered the primary emphasis has been on solutions of the acoustic wave equation with point force where the sound speed varies with height above the ground corresponding to the assumed temperature profile. The method used to obtain the solution of the wave equation is based on Hankel transformation of the wave equation, approximate solution of the transformed equation for wavelength small compared to the scale of the temperature (or sound speed) profile, and approximate or numerical inversion of the Hankel transformed solution. The solution displays the characteristics found in experimental data but extensive comparison between the models and experimental data has not been carried out.

Funneled focusing of planar acoustic waves utilizing the metamaterial properties of an acoustic lens

NASA Astrophysics Data System (ADS)

Walker, E.; Reyes, D.; Rojas, M. M.; Krokhin, A.; Neogi, A.

2014-02-01

Metamaterial acoustic lenses are acoustic devices based on phononic crystal structures that take advantage of negative or near-zero indices of refraction. These unique properties arise due to either the antiparallel direction of the phase and group velocity or strongly anisotropic dispersion characteristics, usually above the first transmission band. In this study, we utilize an FDTD program to examine two phononic lenses that utilize anisotropic effects available in their second band to collimate and focus acoustic waves from a plane-wave source with a k00 wavevector. The phononic crystals consist of stainless steel rods arranged in a square lattice with water as the ambient material. Results show collimation and focusing in the second band for select frequencies, fc ± 0.005𝑓𝑐.

Heat transport by phonons in crystalline materials and nanostructures

NASA Astrophysics Data System (ADS)

Koh, Yee Kan

This dissertation presents experimental studies of heat transport by phonons in crystalline materials and nanostructures, and across solid-solid interfaces. Particularly, this dissertation emphasizes advancing understanding of the mean-free-paths (i.e., the distance phonons propagate without being scattered) of acoustic phonons, which are the dominant heat carriers in most crystalline semiconductor nanostructures. Two primary tools for the studies presented in this dissertation are time-domain thermoreflectance (TDTR) for measurements of thermal conductivity of nanostructures and thermal conductance of interfaces; and frequency-domain thermoreflectance (FDTR), which I developed as a direct probe of the mean-free-paths of dominant heat-carrying phonons in crystalline solids. The foundation of FDTR is the dependence of the apparent thermal conductivity on the frequency of periodic heat sources. I find that the thermal conductivity of semiconductor alloys (InGaP, InGaAs, and SiGe) measured by TDTR depends on the modulation frequency, 0.1 ≤ f ≤ 10 MHz, used in TDTR measurements. Reduction in the thermal conductivity of the semiconductor alloys at high f compares well to the reduction in the thermal conductivity of epitaxial thin films, indicating that frequency dependence and thickness dependence of thermal conductivity are fundamentally equivalent. I developed the frequency dependence of thermal conductivity into a convenient probe of phonon mean-free-paths, a technique which I call frequency-domain thermoreflectance (FDTR). In FDTR, I monitor the changes in the intensity of the reflected probe beam as a function of the modulation frequency. To facilitate the analysis of FDTR measurements, I developed a nonlocal theory for heat conduction by phonons at high heating frequencies. Calculations of the nonlocal theory confirm my experimental findings that phonons with mean-free-paths longer than two times the penetration depth do not contribute to the apparent thermal

Quantitative Evaluations of the Effects of the Seabed Sediments on Scattering and Propagation of Acoustics Energy in Shallow Oceans

DTIC Science & Technology

1999-09-30

Dec. (1998) Yamamoto, T., “ A poroelastic model of highly permeable rocks,” Geophysics, revised August 1999a. Yamamoto, T., “ Acoustical imaging of...scattering mechanisms (volume fluctuation, bottom and sub-bottom roughness) on the acoustic propagation and scattering, and the effects of poroelastic ...properties of the sediments on the propagation of acoustic waves. OBJECTIVES To develop a universal (forward/inverse) model for the seafloor roughness

Temperature Dependence of Phonons in Pyrolitic Graphite

DOE R&D Accomplishments Database

Brockhouse, B. N.; Shirane, G.

1977-01-01

Dispersion curves for longitudinal and transverse phonons propagating along and near the c-axis in pyrolitic graphite at temperatures between 4?K and 1500?C have been measured by neutron spectroscopy. The observed frequencies decrease markedly with increasing temperature (except for the transverse optical ''rippling'' modes in the hexagonal planes). The neutron groups show interesting asymmetrical broadening ascribed to interference between one phonon and many phonon processes.

Phonons in self-assembled Ge/Si structures

NASA Astrophysics Data System (ADS)

Milekhin, A. G.; Nikiforov, A. I.; Pchelyakov, O. P.; Schulze, S.; Zahn, D. R. T.

2002-03-01

We present the results of an investigation dealing with fundamental vibrations in periodical Ge/Si structures with small-size Ge quantum dots (QDs) performed using macro- and micro-Raman spectroscopy under resonant and off-resonant conditions. Samples with different number of repetition of Ge and Si layers contain Ge QDs with an average dot base size of 15 nm and a QD height of 2 nm. Periodic oscillations observed in the low-frequency region of the Raman spectra are assigned to folded LA phonons in the Ge QD superlattices. The measured phonon frequencies are in a good agreement with those calculated using the Rytov model. These oscillations are superimposed with a broad continuous emission originating from the whole acoustic dispersion branch due to a breaking up of translational invariance. The Raman spectra of the structure with single Ge QD layer reveal a series of peaks corresponding to LA phonons localized in the Si layer. Using the measured phonon frequencies and corresponding wave vectors the dispersion of the LA phonons in the Si is obtained. The longitudinal-acoustic wave velocity determined from the dispersion is 8365 ms-1 and in excellent agreement with that derived from the Brillouin study. In the optical phonon range, the LO and TO phonons localized in Ge QDs are observed. The position of the LO Ge phonons shifts downwards with increasing excitation energy (from 2.5 to 2.7 eV) indicating the presence of a QD size distribution in Ge dot superlattices. Raman scattering from Ge QDs is size-selectively enhanced by the resonance of the exciting laser energy and the confined excitonic states.

Phonon Spectrum Engineering in Rolled-up Micro- and Nano-Architectures

DOE PAGES

Fomin, Vladimir M.; Balandin, Alexander A.

2015-10-10

We report on a possibility of efficient engineering of the acoustic phonon energy spectrum in multishell tubular structures produced by a novel high-tech method of self-organization of micro- and nano-architectures. The strain-driven roll-up procedure paved the way for novel classes of metamaterials such as single semiconductor radial micro- and nano-crystals and multi-layer spiral micro- and nano-superlattices. The acoustic phonon dispersion is determined by solving the equations of elastodynamics for InAs and GaAs material systems. It is shown that the number of shells is an important control parameter of the phonon dispersion together with the structure dimensions and acoustic impedance mismatchmore » between the superlattice layers. The obtained results suggest that rolled up nano-architectures are promising for thermoelectric applications owing to a possibility of significant reduction of the thermal conductivity without degradation of the electronic transport.« less

Phonon Spectrum Engineering in Rolled-up Micro- and Nano-Architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fomin, Vladimir M.; Balandin, Alexander A.

We report on a possibility of efficient engineering of the acoustic phonon energy spectrum in multishell tubular structures produced by a novel high-tech method of self-organization of micro- and nano-architectures. The strain-driven roll-up procedure paved the way for novel classes of metamaterials such as single semiconductor radial micro- and nano-crystals and multi-layer spiral micro- and nano-superlattices. The acoustic phonon dispersion is determined by solving the equations of elastodynamics for InAs and GaAs material systems. It is shown that the number of shells is an important control parameter of the phonon dispersion together with the structure dimensions and acoustic impedance mismatchmore » between the superlattice layers. The obtained results suggest that rolled up nano-architectures are promising for thermoelectric applications owing to a possibility of significant reduction of the thermal conductivity without degradation of the electronic transport.« less

The acoustic adaptation hypothesis in a widely distributed South American frog: Southernmost signals propagate better.

PubMed

Velásquez, Nelson A; Moreno-Gómez, Felipe N; Brunetti, Enzo; Penna, Mario

2018-05-03

Animal communication occurs in environments that affect the properties of signals as they propagate from senders to receivers. We studied the geographic variation of the advertisement calls of male Pleurodema thaul individuals from eight localities in Chile. Furthermore, by means of signal propagation experiments, we tested the hypothesis that local calls are better transmitted and less degraded than foreign calls (i.e. acoustic adaptation hypothesis). Overall, the advertisement calls varied greatly along the distribution of P. thaul in Chile, and it was possible to discriminate localities grouped into northern, central and southern stocks. Propagation distance affected signal amplitude and spectral degradation in all localities, but temporal degradation was only affected by propagation distance in one out of seven localities. Call origin affected signal amplitude in five out of seven localities and affected spectral and temporal degradation in six out of seven localities. In addition, in northern localities, local calls degraded more than foreign calls, and in southern localities the opposite was observed. The lack of a strict optimal relationship between signal characteristics and environment indicates partial concordance with the acoustic adaptation hypothesis. Inter-population differences in selectivity for call patterns may compensate for such environmental constraints on acoustic communication.

Nonlinear Effects in Long Range Underwater Acoustic Propagation

DTIC Science & Technology

1985-11-01

Introduction to the Theory of Sound ransmission with Application to the Ocean (McGraw-Hill Book Co., Inc., New York). Oppenheim, Alan V., and Ronald W. Schafer...34Propagation of Finite-Amplitude Sound Waves in an Inhomogeneous Medium with Caustics," Sov. Phys.-Acoust. 22, 516-520. Panton, Ronald L. (1984...21 W. A. Kuperman 22 B. E. McDonald Naval Ocean Research and Development Activity NSTL Station, MS 39529 23 Attn: R. A. Wagstaff New London Laboratory

Dispersion, mode-mixing and the electron-phonon interaction in nanostructures

NASA Astrophysics Data System (ADS)

Dyson, A.; Ridley, B. K.

2018-03-01

The electron-phonon interaction with polar optical modes in nanostructures is re-examined in the light of phonon dispersion relations and the role of the Fuchs-Kliewer (FK) mode. At an interface between adjacent polar materials the frequencies of the FK mode are drawn from the dielectric constants of the adjacent materials and are significantly smaller than the corresponding frequencies of the longitudinal optic (LO) modes at the zone centre. The requirement that all polar modes satisfy mechanical and electrical boundary conditions forces the modes to become hybrids. For a hybrid to have both FK and LO components the LO mode must have the FK frequency, which can only come about through the reduction associated with phonon dispersion relations. We illustrate the effect of phonon dispersion relations on the Fröhlich interaction by considering a simple linear-chain model of the zincblende lattice. Optical and acoustic modes become mixed towards short wavelengths in both optical and acoustic branches. A study of GaAs, InP and cubic GaN and AlN shows that the polarity of the optical branch and the acousticity of the acoustic branch are reduced by dispersion in equal measures, but the effect is relatively weak. Coupling coefficients quantifying the strengths of the interaction with electrons for optical and acoustic components of mixed modes in the optical branch show that, in most cases, the polar interaction dominates the acoustic interaction, and it is reduced from the long-wavelength result towards the zone boundary by only a few percent. The effect on the lower-frequency FK mode can be large.

Heterodyne x-ray diffuse scattering from coherent phonons

DOE PAGES

Kozina, M.; Trigo, M.; Chollet, M.; ...

2017-08-10

Here in this paper, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons frommore » the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.« less

Propagation modeling for sperm whale acoustic clicks in the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Udovydchenkov, Ilya A.; Rypina, Irina I.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.; Newcomb, Joal; Fisher, Robert

2004-05-01

Simulations of acoustic broadband (500-6000 Hz) pulse propagation in the northern Gulf of Mexico, based on environmental data collected as a part of the Littoral Acoustic Demonstration Center (LADC) experiments in the summers of 2001 and 2002, are presented. The results of the modeling support the hypothesis that consistent spectrogram interference patterns observed in the LADC marine mammal phonation data cannot be explained by the propagation effects for temporal analysis windows corresponding to the duration of an animal click, and may be due to a uniqueness of an individual animal phonation apparatus. The utilization of simulation data for the development of an animal tracking algorithm based on the acoustic recordings of a single bottom-moored hydrophone is discussed. The identification of the bottom and surface reflected clicks from the same animal is attempted. The critical ranges for listening to a deep-water forging animal by a surface receiving system are estimated. [Research supported by ONR.

Three-Dimensional Acoustic Propagation Through Shallow Water Internal, Surface Gravity and Bottom Sediment Waves

DTIC Science & Technology

2011-09-01

energy never ends. I am also very pleased to have Dr. William M. Carey, Dr. Henrik Schmidt, Dr. Glen G. Gawarkiewicz and Dr. Pierre Lermusiaux on my...Internal Waves for Multi- Megameter Acoustic Propagation in the Ocean, J. Acoust. Soc. Amer., Vol. 100, P. 3607-3620, 1996. [6] J.R. Apel , M. Badiey

Effect of inter- and intra-annual thermohaline variability on acoustic propagation

NASA Astrophysics Data System (ADS)

Chu, Peter C.; McDonald, Colleen M.; Kucukosmanoglu, Murat; Judono, Albert; Margolina, Tetyana; Fan, Chenwu

2017-05-01

This paper is to answer the question "How can inter- and intra-annual variability in the ocean be leveraged by the submarine Force?" through quantifying inter- and intra-annual variability in (T, S) fields and in turn underwater acoustic characteristics such as transmission loss, signal excess, and range of detection. The Navy's Generalized Digital Environmental Model (GDEM) is the climatological monthly mean data and represents mean annual variability. An optimal spectral decomposition method is used to produce a synoptic monthly gridded (SMG) (T, S) dataset for the world oceans with 1° ×1° horizontal resolution, 28 vertical levels (surface to 3,000 m depth), monthly time increment from January 1945 to December 2014 now available at the NOAA/NCEI website: http://data.nodc.noaa.gov/cgibin/iso?id=gov.noaa.nodc:0140938. The sound velocity decreases from 1945 to 1975 and increases afterwards due to global climate change. Effect of the inter- and intra-annual (T, S) variability on acoustic propagation in the Yellow Sea is investigated using a well-developed acoustic model (Bellhop) in frequencies from 3.5 kHz to 5 kHz with sound velocity profile (SVP) calculated from GDEM and SMG datasets, various bottom types (silty clay, fine sand, gravelly mud, sandy mud, and cobble or gravel) from the NAVOCEANO`s High Frequency Environmental Algorithms (HFEVA), source and receiver depths. Acoustic propagation ranges are extended drastically due to the inter-annual variability in comparison with the climatological SVP (from GDEM). Submarines' vulnerability of detection as its depth varies and avoidance of short acoustic range due to inter-annual variability are also discussed.

Phonon transport properties of two-dimensional group-IV materials from ab initio calculations

NASA Astrophysics Data System (ADS)

Peng, Bo; Zhang, Hao; Shao, Hezhu; Xu, Yuanfeng; Ni, Gang; Zhang, Rongjun; Zhu, Heyuan

2016-12-01

It has been argued that stanene has lowest lattice thermal conductivity among two-dimensional (2D) group-IV materials because of its largest atomic mass, weakest interatomic bonding, and enhanced ZA phonon scattering due to the breaking of an out-of-plane symmetry selection rule. However, we show that, although the lattice thermal conductivity κ for graphene, silicene, and germanene decreases monotonically with decreasing Debye temperature, unexpected higher κ is observed in stanene. By enforcing all the invariance conditions in 2D materials and including Ge 3 d and Sn 4 d electrons as valence electrons for germanene and stanene, respectively, the lattice dynamics in these materials are accurately described. A large acoustic-optical gap and the bunching of the acoustic-phonon branches significantly reduce phonon scattering in stanene, leading to higher thermal conductivity than germanene. The vibrational origin of the acoustic-optical gap can be attributed to the buckled structure. Interestingly, a buckled system has two competing influences on phonon transport: the breaking of the symmetry selection rule leads to reduced thermal conductivity, and the enlarging of the acoustic-optical gap results in enhanced thermal conductivity. The size dependence of thermal conductivity is investigated as well. In nanoribbons, the κ of silicene, germanene, and stanene is much less sensitive to size effect due to their short intrinsic phonon mean-free paths. This work sheds light on the nature of phonon transport in buckled 2D materials.

Modeling of acoustic emission signal propagation in waveguides.

PubMed

Zelenyak, Andreea-Manuela; Hamstad, Marvin A; Sause, Markus G R

2015-05-21

Acoustic emission (AE) testing is a widely used nondestructive testing (NDT) method to investigate material failure. When environmental conditions are harmful for the operation of the sensors, waveguides are typically mounted in between the inspected structure and the sensor. Such waveguides can be built from different materials or have different designs in accordance with the experimental needs. All these variations can cause changes in the acoustic emission signals in terms of modal conversion, additional attenuation or shift in frequency content. A finite element method (FEM) was used to model acoustic emission signal propagation in an aluminum plate with an attached waveguide and was validated against experimental data. The geometry of the waveguide is systematically changed by varying the radius and height to investigate the influence on the detected signals. Different waveguide materials were implemented and change of material properties as function of temperature were taken into account. Development of the option of modeling different waveguide options replaces the time consuming and expensive trial and error alternative of experiments. Thus, the aim of this research has important implications for those who use waveguides for AE testing.

A new class of tunable hypersonic phononic crystals based on polymer-tethered colloids

PubMed Central

Alonso-Redondo, E.; Schmitt, M.; Urbach, Z.; Hui, C. M.; Sainidou, R.; Rembert, P.; Matyjaszewski, K.; Bockstaller, M. R.; Fytas, G.

2015-01-01

The design and engineering of hybrid materials exhibiting tailored phononic band gaps are fundamentally relevant to innovative material technologies in areas ranging from acoustics to thermo-optic devices. Phononic hybridization gaps, originating from the anti-crossing between local resonant and propagating modes, have attracted particular interest because of their relative robustness to structural disorder and the associated benefit to ‘manufacturability'. Although hybridization gap materials are well known, their economic fabrication and efficient control of the gap frequency have remained elusive because of the limited property variability and expensive fabrication methodologies. Here we report a new strategy to realize hybridization gap materials by harnessing the ‘anisotropic elasticity' across the particle–polymer interface in densely polymer-tethered colloidal particles. Theoretical and Brillouin scattering analysis confirm both the robustness to disorder and the tunability of the resulting hybridization gap and provide guidelines for the economic synthesis of new materials with deliberately controlled gap position and width frequencies. PMID:26390851

A new class of tunable hypersonic phononic crystals based on polymer-tethered colloids.

PubMed

Alonso-Redondo, E; Schmitt, M; Urbach, Z; Hui, C M; Sainidou, R; Rembert, P; Matyjaszewski, K; Bockstaller, M R; Fytas, G

2015-09-22

The design and engineering of hybrid materials exhibiting tailored phononic band gaps are fundamentally relevant to innovative material technologies in areas ranging from acoustics to thermo-optic devices. Phononic hybridization gaps, originating from the anti-crossing between local resonant and propagating modes, have attracted particular interest because of their relative robustness to structural disorder and the associated benefit to 'manufacturability'. Although hybridization gap materials are well known, their economic fabrication and efficient control of the gap frequency have remained elusive because of the limited property variability and expensive fabrication methodologies. Here we report a new strategy to realize hybridization gap materials by harnessing the 'anisotropic elasticity' across the particle-polymer interface in densely polymer-tethered colloidal particles. Theoretical and Brillouin scattering analysis confirm both the robustness to disorder and the tunability of the resulting hybridization gap and provide guidelines for the economic synthesis of new materials with deliberately controlled gap position and width frequencies.

Fiber optical vibrometer based on a phononic crystal filter

NASA Astrophysics Data System (ADS)

Lin, Sijing; Chai, Quan; Zhang, Jianzhong

2012-02-01

We propose that phononic crystals could be used as a packaging method in a fiber optical vibrometer system to filter the vibration at unwanted frequency range. A simple FBG based vibrometer and a aluminum-silicone rubber based 1D phononic crystal with the designed phononic band gap are built up, and the corresponding experimental results are demonstrated to show the feasibility of our proposal. Our proposal also points out that optical fiber sensors could be an excellent candidate to research the inner acoustic response of more complex phononic crystals.

Broadband acoustic wave propagation across sloping topography covered by sea ice

NASA Astrophysics Data System (ADS)

Badiey, M.; Wan, L.; Eickmeier, J.; Muenchow, A.; Ryan, P. A.

2017-12-01

The Canada Basin Acoustic Propagation Experiment (CANAPE) quantifies how sound generated in the deep Basin is received on the continental shelf. The two regimes, deep basin and shallow shelves, are separated by a 30-km wide region where the bottom changes from 1000-m to 100-m. This narrow region focuses and traps kinetic energy that surface wind forcing inputs into the ocean over a wide region with periodicities of days to months. As a result, ocean temperature and speed of sound are more variable near sloping topography than they are over either deep basins or shallow shelves. In contrast to companion CANAPE presentations in this session, here we use sound speed as input to predict likely propagation paths and transmission losses across the continental slope with a two-dimensional parabolic model (2D PE). Intensity fluctuations due to the changing bathymetry, water column oceanography, and the scattering from ice cover for broadband signals are checked against measured broadband acoustic signals that were collected simultaneously with the oceanographic measurements for a long period. Differences between measured and calculated transmission loss can be the result of out of plane acoustic paths requiring 3D PE modeling for future studies. [Work supported by ONR code 322 OA].

Staggered-grid finite-difference acoustic modeling with the Time-Domain Atmospheric Acoustic Propagation Suite (TDAAPS).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aldridge, David Franklin; Collier, Sandra L.; Marlin, David H.

2005-05-01

This document is intended to serve as a users guide for the time-domain atmospheric acoustic propagation suite (TDAAPS) program developed as part of the Department of Defense High-Performance Modernization Office (HPCMP) Common High-Performance Computing Scalable Software Initiative (CHSSI). TDAAPS performs staggered-grid finite-difference modeling of the acoustic velocity-pressure system with the incorporation of spatially inhomogeneous winds. Wherever practical the control structure of the codes are written in C++ using an object oriented design. Sections of code where a large number of calculations are required are written in C or F77 in order to enable better compiler optimization of these sections. Themore » TDAAPS program conforms to a UNIX style calling interface. Most of the actions of the codes are controlled by adding flags to the invoking command line. This document presents a large number of examples and provides new users with the necessary background to perform acoustic modeling with TDAAPS.« less

Ultra-high-Q phononic resonators on-chip at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Kharel, Prashanta; Chu, Yiwen; Power, Michael; Renninger, William H.; Schoelkopf, Robert J.; Rakich, Peter T.

2018-06-01

Long-lived, high-frequency phonons are valuable for applications ranging from optomechanics to emerging quantum systems. For scientific as well as technological impact, we seek high-performance oscillators that offer a path toward chip-scale integration. Confocal bulk acoustic wave resonators have demonstrated an immense potential to support long-lived phonon modes in crystalline media at cryogenic temperatures. So far, these devices have been macroscopic with cm-scale dimensions. However, as we push these oscillators to high frequencies, we have an opportunity to radically reduce the footprint as a basis for classical and emerging quantum technologies. In this paper, we present novel design principles and simple microfabrication techniques to create high performance chip-scale confocal bulk acoustic wave resonators in a wide array of crystalline materials. We tailor the acoustic modes of such resonators to efficiently couple to light, permitting us to perform a non-invasive laser-based phonon spectroscopy. Using this technique, we demonstrate an acoustic Q-factor of 2.8 × 107 (6.5 × 106) for chip-scale resonators operating at 12.7 GHz (37.8 GHz) in crystalline z-cut quartz (x-cut silicon) at cryogenic temperatures.

A Finite Difference Numerical Model for the Propagation of Finite Amplitude Acoustical Blast Waves Outdoors Over Hard and Porous Surfaces

DTIC Science & Technology

1991-09-01

Difference Numerical Model for the Propagation of Finite Amplitude Acoustical Blast Waves Outdoors Over Hard and Porous Surfaces by Victor W. Sparrow...The nonlinear acoustic propagation effects require a numerical solution in the time domain. To model a porous ground surface, which in the frequency...incident on the hard and porous surfaces were produced. The model predicted that near grazing finite amplitude acoustic blast waves decay with distance

Influence of Controlled Viscous Dissipation on Propagation of Strongly Nonlinear Waves in Steel-Based Phononic Crystals

NASA Astrophysics Data System (ADS)

Herbold, Eric

2005-07-01

Strongly nonlinear phononic crystals were assembled from chains of stainless steel spheres with diameter 4.78 mm. Propagation of solitary waves and splitting of initial pulse into train of solitary waves excited by the impact of piston was investigated in different viscous media in experiments and in numerical calculations. Oil of various grades was used to introduce controlled dissipation into the system. Preliminary results indicate that splitting of the initial pulse into the train of solitary waves was dramatically influenced by viscosity. This work was supported by NSF (Grant No. DCMS03013220).

Effect of Internal Solitary Waves on Underwater Acoustic Propagation

DTIC Science & Technology

2010-01-01

and 760 m from an expendable bathyther- mograph and one temperature profile below 760 m from the Navy’s Gen- eralized Digital Environment Model ( GDEM ...To calculate sound speed, the GDEM (average of July and August) salinity profile (nearest to CMB) was used. The sound speeds calculated from the GDEM ...from the GDEM sa- linity profile and 424 temperature pro- files generated the range-dependent SSPs (Figure 6). Comparison of the acoustic propagation

A Fusion Model of Seismic and Hydro-Acoustic Propagation for Treaty Monitoring

NASA Astrophysics Data System (ADS)

Arora, Nimar; Prior, Mark

2014-05-01

We present an extension to NET-VISA (Network Processing Vertically Integrated Seismic Analysis), which is a probabilistic generative model of the propagation of seismic waves and their detection on a global scale, to incorporate hydro-acoustic data from the IMS (International Monitoring System) network. The new model includes the coupling of seismic waves into the ocean's SOFAR channel, as well as the propagation of hydro-acoustic waves from underwater explosions. The generative model is described in terms of multiple possible hypotheses -- seismic-to-hydro-acoustic, under-water explosion, other noise sources such as whales singing or icebergs breaking up -- that could lead to signal detections. We decompose each hypothesis into conditional probability distributions that are carefully analyzed and calibrated. These distributions include ones for detection probabilities, blockage in the SOFAR channel (including diffraction, refraction, and reflection around obstacles), energy attenuation, and other features of the resulting waveforms. We present a study of the various features that are extracted from the hydro-acoustic waveforms, and their correlations with each other as well the source of the energy. Additionally, an inference algorithm is presented that concurrently infers the seismic and under-water events, and associates all arrivals (aka triggers), both from seismic and hydro-acoustic stations, to the appropriate event, and labels the path taken by the wave. Finally, our results demonstrate that this fusion of seismic and hydro-acoustic data leads to very good performance. A majority of the under-water events that IDC (International Data Center) analysts built in 2010 are correctly located, and the arrivals that correspond to seismic-to-hydroacoustic coupling, the T phases, are mostly correctly identified. There is no loss in the accuracy of seismic events, in fact, there is a slight overall improvement.

The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride.

PubMed

Kim, Kris S; Trajanoski, Daniel; Ho, Kevin; Gilburd, Leonid; Maiti, Aniket; van der Velden, Luuk; de Beer, Sissi; Walker, Gilbert C

2017-07-06

In order to apply the ability of hexagonal boron nitride (hBN) to confine energy in the form of hyperbolic phonon polariton (HPhP) modes in photonic-electronic devices, approaches to finely control and leverage the sensitivity of these propagating waves must be investigated. Here, we show that by surrounding hBN with materials of lower/higher dielectric responses, such as air and silicon, lower/higher surface momenta of HPhPs can be achieved. Furthermore, an alternative method for preparing thin hBN crystals with minimum contamination is presented, which provides opportunities to study the sensitivity of the damping mechanism of HPhPs on adsorbed materials. Infrared scanning near-field optical microscopy (IR-SNOM) results suggest that the reflections at the upper and lower hBN interfaces are primary causes of the damping of HPhPs, and that the damping coefficients of propagating waves are highly sensitive to adjacent layers, suggesting opportunities for sensor applications.

Analysis of coiled stator ultrasound motor: Fundamental study on analysis of wave propagation on acoustic waveguide for coiled stator

NASA Astrophysics Data System (ADS)

Ozeki, Seiya; Kurita, Keisuke; Uehara, Choyu; Nakane, Noriaki; Sato, Toshio; Takeuchi, Shinichi

2018-07-01

In our research group, we previously developed a coiled stator ultrasound motor (CS-USM) for medical applications such as intravascular ultrasound (IVUS) devices. However, wave propagation on acoustic waveguides has not been investigated sufficiently in previous studies. In this study, we analyze the propagation velocity of elastic waves from the simulated the vibration displacement mode profile along a straight line acoustic waveguide via three-dimensional finite element method (FEM). Concerning results, elastic waves with vibration displacement along the thickness direction show dispersion characteristics corresponding to the a0 and a1 mode plate waves (Lamb waves) in the acoustic waveguide. Our theoretical hypotheses of the propagation velocities were closely borne out by experimental results. We further find that the dispersion characteristic is affected by the width of the acoustic waveguide. We believe that our findings can contribute to improved CS-USM designs for practical application.

Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves.

PubMed

Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C

2013-11-01

An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging.

Design of materials configurations for enhanced phononic and electronic properties

NASA Astrophysics Data System (ADS)

Daraio, Chiara

The discovery of novel nonlinear dynamic and electronic phenomena is presented for the specific cases of granular materials and carbon nanotubes. This research was conducted for designing and constructing optimized macro-, micro- and nano-scale structural configurations of materials, and for studying their phononic and electronic behavior. Variation of composite arrangements of granular elements with different elastic properties in a linear chain-of-sphere, Y-junction or 3-D configurations led to a variety of novel phononic phenomena and interesting physical properties, which can be potentially useful for security, communications, mechanical and biomedical engineering applications. Mechanical and electronic properties of carbon nanotubes with different atomic arrangements and microstructures were also investigated. Electronic properties of Y-junction configured carbon nanotubes exhibit an exciting transistor switch behavior which is not seen in linear configuration nanotubes. Strongly nonlinear materials were designed and fabricated using novel and innovative concepts. Due to their unique strongly nonlinear and anisotropic nature, novel wave phenomena have been discovered. Specifically, violations of Snell's law were detected and a new mechanism of wave interaction with interfaces between NTPCs (Nonlinear Tunable Phononic Crystals) was established. Polymer-based systems were tested for the first time, and the tunability of the solitary waves speed was demonstrated. New materials with transformed signal propagation speed in the manageable range of 10-100 m/s and signal amplitude typical for audible speech have been developed. The enhancing of the mitigation of solitary and shock waves in 1-D chains were demonstrated and a new protective medium was designed for practical applications. 1-D, 2-D and 3-D strongly nonlinear system have been investigated providing a broad impact on the whole area of strongly nonlinear wave dynamics and creating experimental basis for new

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wavemore » trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.« less

Picosecond phase-velocity dispersion of hypersonic phonons imaged with ultrafast electron microscopy

DOE PAGES

Cremons, Daniel R.; Du, Daniel X.; Flannigan, David J.

2017-12-05

We describe the direct imaging—with four-dimensional ultrafast electron microscopy—of the emergence, evolution, dispersion, and decay of photoexcited, hypersonic coherent acoustic phonons in nanoscale germanium wedges. Coherent strain waves generated via ultrafast in situ photoexcitation were imaged propagating with initial phase velocities of up to 35 km/s across discrete micrometer-scale crystal regions. We then observe that, while each wave front travels at a constant velocity, the entire wave train evolves with a time-varying phase-velocity dispersion, displaying a single-exponential decay to the longitudinal speed of sound (5 km/s) and with a mean lifetime of 280 ps. We also find that the wavemore » trains propagate along a single in-plane direction oriented parallel to striations introduced during specimen preparation, independent of crystallographic direction. Elastic-plate modeling indicates the dynamics arise from excitation of a single, symmetric (dilatational) guided acoustic mode. Further, by precisely determining the experiment time-zero position with a plasma-lensing method, we find that wave-front emergence occurs approximately 100 ps after femtosecond photoexcitation, which matches well with Auger recombination times in germanium. We conclude by discussing the similarities between the imaged hypersonic strain-wave dynamics and electron/hole plasma-wave dynamics in strongly photoexcited semiconductors.« less

Acoustic propagation in curved ducts with extended reacting wall treatment

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.

1989-01-01

A finite-element Galerkin formulation was employed to study the attenuation of acoustic waves propagating in two-dimensional S-curved ducts with absorbing walls without a mean flow. The reflection and transmission at the entrance and the exit of a curved duct were determined by coupling the finite-element solutions in the curved duct to the eigenfunctions of an infinite, uniform, hard wall duct. In the frequency range where the duct height and acoustic wave length are nearly equal, the effects of duct length, curvature (duct offset) and absorber thickness were examined. For a given offset in the curved duct, the length of the S-duct was found to significantly affect both the absorptive and reflective characteristics of the duct. A means of reducing the number of elements in the absorber region was also presented. In addition, for a curved duct, power attenuation contours were examined to determine conditions for maximum acoustic power absorption. Again, wall curvature was found to significantly effect the optimization process.

Preface to special topic: Selected articles from phononics 2013: The second international conference on phononic crystals/metamaterials, phonon transport and optomechanics, 2-7 June 2013, Sharm El-Sheikh, Egypt

DOE PAGES

Hussein, Mahmoud I.; El-Kady, Ihab; Li, Baowen; ...

2014-12-31

“Phononics” is an interdisciplinary branch of physics and engineering that deals with the behavior of phonons, and more broadly elastic and acoustic waves in similar context, and their manipulation in solids and/or fluids to benefit technological applications. Compared to resembling disciplines, such as electronics and photonics, phononics is a youthful field. It is growing at a remarkable rate, especially when viewed liberally with no limiting constraints on any particular length scale, discipline or application.

Preface to special topic: Selected articles from phononics 2013: The second international conference on phononic crystals/metamaterials, phonon transport and optomechanics, 2-7 June 2013, Sharm El-Sheikh, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hussein, Mahmoud I.; El-Kady, Ihab; Li, Baowen

“Phononics” is an interdisciplinary branch of physics and engineering that deals with the behavior of phonons, and more broadly elastic and acoustic waves in similar context, and their manipulation in solids and/or fluids to benefit technological applications. Compared to resembling disciplines, such as electronics and photonics, phononics is a youthful field. It is growing at a remarkable rate, especially when viewed liberally with no limiting constraints on any particular length scale, discipline or application.

Application of the Parabolic Approximation to Predict Acoustical Propagation in the Ocean.

ERIC Educational Resources Information Center

McDaniel, Suzanne T.

1979-01-01

A simplified derivation of the parabolic approximation to the acoustical wave equation is presented. Exact solutions to this approximate equation are compared with solutions to the wave equation to demonstrate the applicability of this method to the study of underwater sound propagation. (Author/BB)

Phonon Networks with Silicon-Vacancy Centers in Diamond Waveguides

NASA Astrophysics Data System (ADS)

Lemonde, M.-A.; Meesala, S.; Sipahigil, A.; Schuetz, M. J. A.; Lukin, M. D.; Loncar, M.; Rabl, P.

2018-05-01

We propose and analyze a novel realization of a solid-state quantum network, where separated silicon-vacancy centers are coupled via the phonon modes of a quasi-one-dimensional diamond waveguide. In our approach, quantum states encoded in long-lived electronic spin states can be converted into propagating phonon wave packets and be reabsorbed efficiently by a distant defect center. Our analysis shows that under realistic conditions, this approach enables the implementation of high-fidelity, scalable quantum communication protocols within chip-scale spin-qubit networks. Apart from quantum information processing, this setup constitutes a novel waveguide QED platform, where strong-coupling effects between solid-state defects and individual propagating phonons can be explored at the quantum level.

Phonon Networks with Silicon-Vacancy Centers in Diamond Waveguides.

PubMed

Lemonde, M-A; Meesala, S; Sipahigil, A; Schuetz, M J A; Lukin, M D; Loncar, M; Rabl, P

2018-05-25

We propose and analyze a novel realization of a solid-state quantum network, where separated silicon-vacancy centers are coupled via the phonon modes of a quasi-one-dimensional diamond waveguide. In our approach, quantum states encoded in long-lived electronic spin states can be converted into propagating phonon wave packets and be reabsorbed efficiently by a distant defect center. Our analysis shows that under realistic conditions, this approach enables the implementation of high-fidelity, scalable quantum communication protocols within chip-scale spin-qubit networks. Apart from quantum information processing, this setup constitutes a novel waveguide QED platform, where strong-coupling effects between solid-state defects and individual propagating phonons can be explored at the quantum level.

Apparatus for in situ prediction of the thermal conductivity of fiberglass batts using acoustic propagation constant

NASA Astrophysics Data System (ADS)

Tinianov, Brandon D.; Nakagawa, Masami; Muñoz, David R.

2006-02-01

This article describes a novel technique for the measurement of the thermal conductivity of low-density (12-18kg/m3) fiberglass insulation and other related fibrous insulation materials using a noninvasive acoustic apparatus. The experimental method is an extension of earlier acoustic methods based upon the evaluation of the propagation constant from the acoustic pressure transfer function across the test material. To accomplish this, an analytical model is employed that describes the behavior of sound waves at the outlet of a baffled waveguide. The model accounts for the behavior of the mixed impedance interface introduced by the test material. Current results show that the technique is stable for a broad range of absorber thicknesses and densities. Experimental results obtained in the laboratory show excellent correlation between the thermal conductivity and both the real and imaginary components of the propagation constant. Correlation of calculated propagation constant magnitude versus measured thermal conductivity gave an R2 of 0.94 for the bulk density range (12-18kg/m3) typical for manufactured fiberglass batt materials. As an improvement to earlier acoustic techniques, measurement is now possible in noisy manufacturing environments with a moving test material. Given the promise of such highly correlated measurements in a robust method, the acoustic technique is well suited to continuously measure the thermal conductivity of the material during its production, replacing current expensive off-line methods. Test cycle time is reduced from hours to seconds.

Influence of crystal quality on the excitation and propagation of surface and bulk acoustic waves in polycrystalline AlN films.

PubMed

Clement, Marta; Olivares, Jimena; Capilla, Jose; Sangrador, Jesús; Iborra, Enrique

2012-01-01

We investigate the excitation and propagation of acoustic waves in polycrystalline aluminum nitride films along the directions parallel and normal to the c-axis. Longitudinal and transverse propagations are assessed through the frequency response of surface acoustic wave and bulk acoustic wave devices fabricated on films of different crystal qualities. The crystalline properties significantly affect the electromechanical coupling factors and acoustic properties of the piezoelectric layers. The presence of misoriented grains produces an overall decrease of the piezoelectric activity, degrading more severely the excitation and propagation of waves traveling transversally to the c-axis. It is suggested that the presence of such crystalline defects in c-axis-oriented films reduces the mechanical coherence between grains and hinders the transverse deformation of the film when the electric field is applied parallel to the surface. © 2012 IEEE

High frequency acoustic propagation under variable sea surfaces

NASA Astrophysics Data System (ADS)

Senne, Joseph

This dissertation examines the effects of rough sea surfaces and sub-surface bubbles on high frequency acoustic transmissions. Owing to the strong attenuation of electromagnetic waves in seawater, acoustic waves are used in the underwater realm much in the same way that electromagnetic waves are used in the atmosphere. The transmission and reception of acoustic waves in the underwater environment is important for a variety of fields including navigation, ocean observation, and real-time communications. Rough sea surfaces and sub-surface bubbles alter the acoustic signals that are received not only in the near-surface water column, but also at depth. This dissertation demonstrates that surface roughness and sub-surface bubbles notably affect acoustic transmissions with frequency ranges typical of underwater communications systems (10-50 kHz). The influence of rough surfaces on acoustic transmissions is determined by modeling forward propagation subject to sea surface dynamics that vary with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Linear surface waves are generated from surface wave spectra, and evolved in time using a Runge-Kutta integration technique. This evolving, range-dependent surface information is combined with other environmental parameters and fed into the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. The influence of sub-surface bubbles on acoustic transmissions is determined by modeling the population of bubbles near the surface and using those populations to approximate the effective changes in sound speed and attenuation. Both range-dependent and range-independent bubble models are

Correspondence between sound propagation in discrete and continuous random media with application to forest acoustics.

PubMed

Ostashev, Vladimir E; Wilson, D Keith; Muhlestein, Michael B; Attenborough, Keith

2018-02-01

Although sound propagation in a forest is important in several applications, there are currently no rigorous yet computationally tractable prediction methods. Due to the complexity of sound scattering in a forest, it is natural to formulate the problem stochastically. In this paper, it is demonstrated that the equations for the statistical moments of the sound field propagating in a forest have the same form as those for sound propagation in a turbulent atmosphere if the scattering properties of the two media are expressed in terms of the differential scattering and total cross sections. Using the existing theories for sound propagation in a turbulent atmosphere, this analogy enables the derivation of several results for predicting forest acoustics. In particular, the second-moment parabolic equation is formulated for the spatial correlation function of the sound field propagating above an impedance ground in a forest with micrometeorology. Effective numerical techniques for solving this equation have been developed in atmospheric acoustics. In another example, formulas are obtained that describe the effect of a forest on the interference between the direct and ground-reflected waves. The formulated correspondence between wave propagation in discrete and continuous random media can also be used in other fields of physics.

Observation of band gaps in the gigahertz range and deaf bands in a hypersonic aluminum nitride phononic crystal slab

NASA Astrophysics Data System (ADS)

Gorisse, M.; Benchabane, S.; Teissier, G.; Billard, C.; Reinhardt, A.; Laude, V.; Defaÿ, E.; Aïd, M.

2011-06-01

We report on the observation of elastic waves propagating in a two-dimensional phononic crystal composed of air holes drilled in an aluminum nitride membrane. The theoretical band structure indicates the existence of an acoustic band gap centered around 800 MHz with a relative bandwidth of 6.5% that is confirmed by gigahertz optical images of the surface displacement. Further electrical measurements and computation of the transmission reveal a much wider attenuation band that is explained by the deaf character of certain bands resulting from the orthogonality of their polarization with that of the source.

Finite size effect on the magnetic excitations spectra, phonons and heat conduction of the quasi- one-dimensional spin chains system SrCuO2

NASA Astrophysics Data System (ADS)

Bounoua, Dalila; Saint-Martin, Romuald; Petit, Sylvain; Bourdarot, Frédéric; Pinsard-Gaudart, Loreynne

2018-05-01

We report inelastic neutron scattering measurements of the phonons modes, in the one-dimensional half integer spin chains cuprate SrCuO2. We study the longitudinal and the transverse modes propagating in the direction of the chains, along Q (0 0 L) and Q (2 0 L), respectively. On the other hand, we investigate the effect of substitution by impurities in the corresponding doped compounds, namely, SrCu0.99M0.01O2 with M=Mg or Zn, and La0.01Sr0.99CuO2. Our results evidence a systematic strong spinon-phonon interaction leading to an important decrease of the phonon scattered intensity as well as a decrease of the group velocity of the transverse acoustic modes upon substitution, and a shift of the transverse optical B3 u mode in the La-doped SrCuO2, in terms of energy.

A frequency domain linearized Navier-Stokes equations approach to acoustic propagation in flow ducts with sharp edges.

PubMed

Kierkegaard, Axel; Boij, Susann; Efraimsson, Gunilla

2010-02-01

Acoustic wave propagation in flow ducts is commonly modeled with time-domain non-linear Navier-Stokes equation methodologies. To reduce computational effort, investigations of a linearized approach in frequency domain are carried out. Calculations of sound wave propagation in a straight duct are presented with an orifice plate and a mean flow present. Results of transmission and reflections at the orifice are presented on a two-port scattering matrix form and are compared to measurements with good agreement. The wave propagation is modeled with a frequency domain linearized Navier-Stokes equation methodology. This methodology is found to be efficient for cases where the acoustic field does not alter the mean flow field, i.e., when whistling does not occur.

THz Acoustic Spectroscopy by using Double Quantum Wells and Ultrafast Optical Spectroscopy.

PubMed

Wei, Fan Jun; Yeh, Yu-Hsiang; Sheu, Jinn-Kong; Lin, Kung-Hsuan

2016-06-27

GaN is a pivotal material for acoustic transducers and acoustic spectroscopy in the THz regime, but its THz phonon properties have not been experimentally and comprehensively studied. In this report, we demonstrate how to use double quantum wells as a THz acoustic transducer for measuring generated acoustic phonons and deriving a broadband acoustic spectrum with continuous frequencies. We experimentally investigated the sub-THz frequency dependence of acoustic attenuation (i.e., phonon mean-free paths) in GaN, in addition to its physical origins such as anharmonic scattering, defect scattering, and boundary scattering. A new upper limit of attenuation caused by anharmonic scattering, which is lower than previously reported values, was obtained. Our results should be noteworthy for THz acoustic spectroscopy and for gaining a fundamental understanding of heat conduction.

A hybrid phononic crystal for roof application.

PubMed

Wan, Qingmian; Shao, Rong

2017-11-01

Phononic crystal is a type of acoustic material, and the study of phononic crystals has attracted great attention from national research institutions. Meanwhile, noise reduction in the low-frequency range has always encountered difficulties and troubles in the engineering field. In order to obtain a unique and effective low-frequency noise reduction method, in this paper a low frequency noise attenuation system based on phononic crystal structure is proposed and demonstrated. The finite element simulation of the band gap is consistent with the final test results. The effects of structure parameters on the band gaps were studied by changing the structure parameters and the band gaps can be controlled by suitably tuning structure parameters. The structure and results provide a good support for phononic crystal structures engineering application.

Studies of elasticity, sound propagation and attenuation of acoustic modes in granular media: final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makse, Hernan A.; Johnson, David L.

2014-09-03

This is the final report describing the results of DOE Grant # DE-FG02-03ER15458 with original termination date of April 31, 2013, which has been extended to April 31, 2014. The goal of this project is to develop a theoretical and experimental understanding of sound propagation, elasticity and dissipation in granular materials. The topic is relevant for the efficient production of hydrocarbon and for identifying and characterizing the underground formation for storage of either CO 2 or nuclear waste material. Furthermore, understanding the basic properties of acoustic propagation in granular media is of importance not only to the energy industry, butmore » also to the pharmaceutical, chemical and agricultural industries. We employ a set of experimental, theoretical and computational tools to develop a study of acoustics and dissipation in granular media. These include the concept effective mass of granular media, normal modes analysis, statistical mechanics frameworks and numerical simulations based on Discrete Element Methods. Effective mass measurements allow us to study the mechanisms of the elastic response and attenuation of acoustic modes in granular media. We perform experiments and simulations under varying conditions, including humidity and vacuum, and different interparticle force-laws to develop a fundamental understanding of the mechanisms of damping and acoustic propagation in granular media. A theoretical statistical approach studies the necessary phase space of configurations in pressure, volume fraction to classify granular materials.« less

Terahertz acoustic phonon detection from a compact surface layer of spherical nanoparticles powder mixture of aluminum, alumina and multi-walled carbon nanotube

NASA Astrophysics Data System (ADS)

Abouelsayed, A.; Ebrahim, M. R.; El hotaby, W.; Hassan, S. A.; Al-Ashkar, Emad

2017-10-01

We present terahertz spectroscopy study on spherical nanoparticles powder mixture of aluminum, alumina, and MWCNTs induced by surface mechanical attrition treatment (SMAT) of aluminum substrates. Surface alloying of AL, Al2O3 0.95% and MWCNTs 0.05% powder mixture was produced during SMAT process, where a compact surface layer of about 200 μm due to ball bombardment was produced from the mixture. Al2O3 alumina powder played a significant role in MWCNTs distribution on surface, those were held in deformation surface cites of micro-cavities due to SMAT process of Al. The benefits are the effects on resulted optical properties of the surface studied at the terahertz frequency range due to electrical isolation confinement effects and electronic resonance disturbances exerted on Al electronic resonance at the same range of frequencies. THz acoustic phonon around 0.53-0.6 THz (17-20 cm-1) were observed at ambient conditions for the spherical nanoparticles powder mixture of Al, Al2O3 and MWCNTs. These results suggested that the presence of Al2O3 and MWCNTs during SMAT process leads to the optically detection of such acoustic phonon in the THz frequency range.

Surface phononic graphene

NASA Astrophysics Data System (ADS)

Yu, Si-Yuan; Sun, Xiao-Chen; Ni, Xu; Wang, Qing; Yan, Xue-Jun; He, Cheng; Liu, Xiao-Ping; Feng, Liang; Lu, Ming-Hui; Chen, Yan-Feng

2016-12-01

Strategic manipulation of wave and particle transport in various media is the key driving force for modern information processing and communication. In a strongly scattering medium, waves and particles exhibit versatile transport characteristics such as localization, tunnelling with exponential decay, ballistic, and diffusion behaviours due to dynamical multiple scattering from strong scatters or impurities. Recent investigations of graphene have offered a unique approach, from a quantum point of view, to design the dispersion of electrons on demand, enabling relativistic massless Dirac quasiparticles, and thus inducing low-loss transport either ballistically or diffusively. Here, we report an experimental demonstration of an artificial phononic graphene tailored for surface phonons on a LiNbO3 integrated platform. The system exhibits Dirac quasiparticle-like transport, that is, pseudo-diffusion at the Dirac point, which gives rise to a thickness-independent temporal beating for transmitted pulses, an analogue of Zitterbewegung effects. The demonstrated fully integrated artificial phononic graphene platform here constitutes a step towards on-chip quantum simulators of graphene and unique monolithic electro-acoustic integrated circuits.

Nonequilibrium dynamics of the phonon gas in ultrafast-excited antimony

NASA Astrophysics Data System (ADS)

Krylow, Sergej; Zijlstra, Eeuwe S.; Kabeer, Fairoja Cheenicode; Zier, Tobias; Bauerhenne, Bernd; Garcia, Martin E.

2017-12-01

The ultrafast relaxation dynamics of a nonequilibrium phonon gas towards thermal equilibrium involves many-body collisions that cannot be properly described by perturbative approaches. Here, we develop a nonperturbative method to elucidate the microscopic mechanisms underlying the decay of laser-excited coherent phonons in the presence of electron-hole pairs, which so far are not fully understood. Our theory relies on ab initio molecular dynamics simulations on laser-excited potential-energy surfaces. Those simulations are compared with runs in which the laser-excited coherent phonon is artificially deoccupied. We apply this method to antimony and show that the decay of the A1 g phonon mode at low laser fluences can be accounted mainly to three-body down-conversion processes of an A1 g phonon into acoustic phonons. For higher excitation strengths, however, we see a crossover to a four-phonon process, in which two A1 g phonons decay into two optical phonons.

Acoustic propagation in a thermally stratified atmosphere

NASA Technical Reports Server (NTRS)

Vanmoorhem, W. K.

1985-01-01

This report describes the activities during the fifth six month period of the investigation of acoustic propagation in the atmosphere with a realistic temperature profile. Progress has been achieved in two major directions: comparisons between the lapse model and experimental data taken by NASA during the second tower experiment, and development of a model propagation in an inversion. Data from the second tower experiment became available near the end of 1984 and some comparisons have been carried out, but this work is not complete. Problems with the temperature profiler during the experiment have produced temperature profiles that are difficult to fit the assumed variation of temperature with height, but in cases where reasonable fits have been obtained agreement between the model and the experiments are close. The major weaknesses in the model appear to be the presence of discontinuities in some regions, the low sound levels predicted near the source height, and difficulties with the argument of the Hankel function being outside the allowable range. Work on the inversion model has progressed slowly, and the rays for that case are discussed along with a simple energy conservation model of sound level enhancement in the inversion case.

Simulation the Effect of Internal Wave on the Acoustic Propagation

NASA Astrophysics Data System (ADS)

Ko, D. S.

2005-05-01

An acoustic radiation transport model with the Monte Carlo solution has been developed and applied to study the effect of internal wave induced random oceanic fluctuations on the deep ocean acoustic propagation. Refraction in the ocean sound channel is performed by means of bi-cubic spline interpolation of discrete deterministic ray paths in the angle(energy)-range-depth coordinates. Scattering by random internal wave fluctuations is accomplished by sampling a power law scattering kernel applying the rejection method. Results from numerical experiments show that the mean positions of acoustic rays are significantly displaced tending toward the sound channel axis due to the asymmetry of the scattering kernel. The spreading of ray depths and angles about the means depends strongly on frequency. The envelope of the ray displacement spreading is found to be proportional to the square root of range which is different from "3/2 law" found in the non-channel case. Suppression of the spreading is due to the anisotropy of fluctuations and especially due to the presence of sound channel itself.

Paracousti-UQ: A Stochastic 3-D Acoustic Wave Propagation Algorithm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Preston, Leiph

Acoustic full waveform algorithms, such as Paracousti, provide deterministic solutions in complex, 3-D variable environments. In reality, environmental and source characteristics are often only known in a statistical sense. Thus, to fully characterize the expected sound levels within an environment, this uncertainty in environmental and source factors should be incorporated into the acoustic simulations. Performing Monte Carlo (MC) simulations is one method of assessing this uncertainty, but it can quickly become computationally intractable for realistic problems. An alternative method, using the technique of stochastic partial differential equations (SPDE), allows computation of the statistical properties of output signals at a fractionmore » of the computational cost of MC. Paracousti-UQ solves the SPDE system of 3-D acoustic wave propagation equations and provides estimates of the uncertainty of the output simulated wave field (e.g., amplitudes, waveforms) based on estimated probability distributions of the input medium and source parameters. This report describes the derivation of the stochastic partial differential equations, their implementation, and comparison of Paracousti-UQ results with MC simulations using simple models.« less

Finite Element Analysis of the Propagation of Acoustic Waves Along Waveguides Immersed in Water

NASA Astrophysics Data System (ADS)

Hladky-Hennion, A.-C.; Langlet, P.; de Billy, M.

1997-03-01

The finite element approach has previously been used, with the help of the ATILA code, to model the propagation of acoustic waves in waveguides [A.-C. Hladky-Hennion, Journal of Sound and Vibration, 194,119-136 (1996)]. In this paper an extension of the technique to the analysis of the propagation of acoustic waves in immersed waveguides is presented. In the proposed approach, the problem is reduced to a bidimensional problem, in which only the cross-section of the guide and the surrounding fluid domain are meshed by using finite elements. Then, wedges the top angles of which vary, are studied and the finite element results of the wedge wave speed are compared with experimental results. Finally, the conclusion indicates a way to extend this approach to waveguides of any cross-section.

The hydrogen-bond network of water supports propagating optical phonon-like modes

DOE PAGES

Elton, Daniel C.; Fernández-Serra, Marivi

2016-01-04

The local structure of liquid water as a function of temperature is a source of intense research. This structure is intimately linked to the dynamics of water molecules, which can be measured using Raman and infrared spectroscopies. The assignment of spectral peaks depends on whether they are collective modes or single-molecule motions. Vibrational modes in liquids are usually considered to be associated to the motions of single molecules or small clusters. Using molecular dynamics simulations, here we find dispersive optical phonon-like modes in the librational and OH-stretching bands. We argue that on subpicosecond time scales these modes propagate through water’smore » hydrogen-bond network over distances of up to 2 nm. In the long wavelength limit these optical modes exhibit longitudinal–transverse splitting, indicating the presence of coherent long-range dipole–dipole interactions, as in ice. Lastly, our results indicate the dynamics of liquid water have more similarities to ice than previously thought.« less

The hydrogen-bond network of water supports propagating optical phonon-like modes.

PubMed

Elton, Daniel C; Fernández-Serra, Marivi

2016-01-04

The local structure of liquid water as a function of temperature is a source of intense research. This structure is intimately linked to the dynamics of water molecules, which can be measured using Raman and infrared spectroscopies. The assignment of spectral peaks depends on whether they are collective modes or single-molecule motions. Vibrational modes in liquids are usually considered to be associated to the motions of single molecules or small clusters. Using molecular dynamics simulations, here we find dispersive optical phonon-like modes in the librational and OH-stretching bands. We argue that on subpicosecond time scales these modes propagate through water's hydrogen-bond network over distances of up to 2 nm. In the long wavelength limit these optical modes exhibit longitudinal-transverse splitting, indicating the presence of coherent long-range dipole-dipole interactions, as in ice. Our results indicate the dynamics of liquid water have more similarities to ice than previously thought.

Acoustic Propagation Studies For Sperm Whale Phonation Analysis During LADC Experiments

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.

2004-11-01

The Littoral Acoustic Demonstration Center (LADC) conducted a series of passive acoustic experiments in the Northern Gulf of Mexico and the Ligurian Sea in 2001 and 2002. Environmental and acoustic moorings were deployed in areas of large concentrations of marine mammals (mainly, sperm whales). Recordings and analysis of whale phonations are among the objectives of the project. Each mooring had a single autonomously recording hydrophone (Environmental Acoustic Recording System (EARS)) obtained from the U.S. Naval Oceanographic Office after modification to record signals up to 5,859 Hz in the Gulf of Mexico and up to 12,500 Hz in the Ligurian Sea. Self-recording environmental sensors, attached to the moorings, and concurrent environmental ship surveys provided the environmental data for the experiments. The results of acoustic simulations of long-range propagation of the broad-band (500-6,000 Hz) phonation pulses from a hypothetical whale location to the recording hydrophone in the experimental environments are presented. The utilization of the simulation results for an interpretation of the spectral features observed in whale clicks and for the development of tracking algorithms from single hydrophone recordings based on the identification of direct and surface and bottom reflected arrivals are discussed. [Research supported by ONR.

Acoustic imaging and mirage effects with high transmittance in a periodically perforated metal slab

NASA Astrophysics Data System (ADS)

Zhao, Sheng-Dong; Wang, Yue-Sheng; Zhang, Chuanzeng

2016-11-01

In this paper, we present a high-quality superlens to focus acoustic waves using a periodically perforated metallic structure which is made of zinc and immersed in water. By changing a geometrical parameter gradually, a kind of gradient-index phononic crystal lens is designed to attain the mirage effects. The acoustic waves can propagate along an arc-shaped trajectory which is precisely controlled by the angle and frequency of the incident waves. The negative refraction imaging effect depends delicately on the transmittance of the solid structure. The acoustic impedance matching between the solid and the liquid proposed in this article, which is determined by the effective density and group velocity of the unit-cell, is significant for overcoming the inefficiency problem of acoustic devices. This study focuses on how to obtain the high transmittance imaging and mirage effects based on the adequate material selection and geometrical design.

Lattice anharmonicity, phonon dispersion, and thermal conductivity of PbTe studied by the phonon quasiparticle approach

NASA Astrophysics Data System (ADS)

Lu, Yong; Sun, Tao; Zhang, Dong-Bo

2018-05-01

We investigated the vibrational property of lead telluride (PbTe) with a focus on lattice anharmonicity at moderate temperatures (300 phonon quasiparticle approach which combines first-principles molecular dynamics and lattice dynamics. The calculated anharmonic phonon dispersions are strongly temperature dependent and some phonon modes adopt giant frequency shifts, e.g., transverse optical modes in the long-wavlength regime. As a result, we witness the avoided crossing between transverse optical modes and longitudinal acoustic modes at elevated temperature, in good agreement with experimentation and available theoretical studies. These results, together with the large root-mean-square displacements of atoms, reveal a strong anharmonic effect in PbTe. The obtained phonon lifetimes allow studies of transport properties. For considered temperatures, the phonon mean free paths can be shorter than lattice constants at relatively high temperature, especially for optical modes. This finding goes against the widely employed minimal phonon mean free path concept. As such, the calculated lattice thermal conductivity of PbTe, which is indeed relatively small, does not have the prescribed minima at high temperature, showcasing the breakdown of the minimal mean free path theory. Our study provides a basis for delineating vibrational and transport properties of PbTe and other thermoelectric materials within the framework of the phonon gas model.

Influences of non-uniform pressure field outside bubbles on the propagation of acoustic waves in dilute bubbly liquids.

PubMed

Zhang, Yuning; Du, Xiaoze

2015-09-01

Predictions of the propagation of the acoustic waves in bubbly liquids is of great importance for bubble dynamics and related applications (e.g. sonochemistry, sonochemical reactor design, biomedical engineering). In the present paper, an approach for modeling the propagation of the acoustic waves in dilute bubbly liquids is proposed through considering the non-uniform pressure field outside the bubbles. This approach is validated through comparing with available experimental data in the literature. Comparing with the previous models, our approach mainly improves the predictions of the attenuation of acoustic waves in the regions with large kR0 (k is the wave number and R0 is the equilibrium bubble radius). Stability of the oscillating bubbles under acoustic excitation are also quantitatively discussed based on the analytical solution. Copyright © 2015 Elsevier B.V. All rights reserved.

Localization of marine mammals near Hawaii using an acoustic propagation model

NASA Astrophysics Data System (ADS)

Tiemann, Christopher O.; Porter, Michael B.; Frazer, L. Neil

2004-06-01

Humpback whale songs were recorded on six widely spaced receivers of the Pacific Missile Range Facility (PMRF) hydrophone network near Hawaii during March of 2001. These recordings were used to test a new approach to localizing the whales that exploits the time-difference of arrival (time lag) of their calls as measured between receiver pairs in the PMRF network. The usual technique for estimating source position uses the intersection of hyperbolic curves of constant time lag, but a drawback of this approach is its assumption of a constant wave speed and straight-line propagation to associate acoustic travel time with range. In contrast to hyperbolic fixing, the algorithm described here uses an acoustic propagation model to account for waveguide and multipath effects when estimating travel time from hypothesized source positions. A comparison between predicted and measured time lags forms an ambiguity surface, or visual representation of the most probable whale position in a horizontal plane around the array. This is an important benefit because it allows for automated peak extraction to provide a location estimate. Examples of whale localizations using real and simulated data in algorithms of increasing complexity are provided.

A chip-integrated coherent photonic-phononic memory.

PubMed

Merklein, Moritz; Stiller, Birgit; Vu, Khu; Madden, Stephen J; Eggleton, Benjamin J

2017-09-18

Controlling and manipulating quanta of coherent acoustic vibrations-phonons-in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk.Optical storage implementations based on optomechanical resonator are limited to one wavelength. Here, exploiting stimulated Brillouin scattering, the authors demonstrate a coherent optical memory based on a planar integrated waveguide, which can operate at different wavelengths without cross-talk.

Global boundary flattening transforms for acoustic propagation under rough sea surfaces.

PubMed

Oba, Roger M

2010-07-01

This paper introduces a conformal transform of an acoustic domain under a one-dimensional, rough sea surface onto a domain with a flat top. This non-perturbative transform can include many hundreds of wavelengths of the surface variation. The resulting two-dimensional, flat-topped domain allows direct application of any existing, acoustic propagation model of the Helmholtz or wave equation using transformed sound speeds. Such a transform-model combination applies where the surface particle velocity is much slower than sound speed, such that the boundary motion can be neglected. Once the acoustic field is computed, the bijective (one-to-one and onto) mapping permits the field interpolation in terms of the original coordinates. The Bergstrom method for inverse Riemann maps determines the transform by iterated solution of an integral equation for a surface matching term. Rough sea surface forward scatter test cases provide verification of the method using a particular parabolic equation model of the Helmholtz equation.

Magnon and phonon thermometry with inelastic light scattering

NASA Astrophysics Data System (ADS)

Olsson, Kevin S.; An, Kyongmo; Li, Xiaoqin

2018-04-01

Spin caloritronics investigates the interplay between the transport of spin and heat. In the spin Seebeck effect, a thermal gradient across a magnetic material generates a spin current. A temperature difference between the energy carriers of the spin and lattice subsystems, namely the magnons and phonons, is necessary for such thermal nonequilibrium generation of spin current. Inelastic light scattering is a powerful method that can resolve the individual temperatures of magnons and phonons. In this review, we discuss the thermometry capabilities of inelastic light scattering for measuring optical and acoustic phonons, as well as magnons. A scattering spectrum offers three temperature sensitive parameters: frequency shift, linewidth, and integrated intensity. We discuss the temperatures measured via each of these parameters for both phonon and magnons. Finally, we discuss inelastic light scattering experiments that have examined the magnon and phonon temperatures in thermal nonequilibrium which are particularly relevant to spin caloritronic phenomena.

Phononic Origins of Friction in Carbon Nanotube Oscillators.

PubMed

Prasad, Matukumilli V D; Bhattacharya, Baidurya

2017-04-12

Phononic coupling can have a significant role in friction between nanoscale surfaces. We find frictional dissipation per atom in carbon nanotube (CNT) oscillators to depend significantly on interface features such as contact area, commensurability, and by end-capping of the inner core. We perform large-scale phonon wavepacket MD simulations to study phonon coupling between a 250 nm long (10,10) outer tube and inner cores of four different geometries. Five different phonon polarizations known to have dominant roles in thermal transport are selected, and transmission coefficient plots for a range of phonon energies along with phonon scattering dynamics at specific energies are obtained. We find that the length of interface affects friction only through LA phonon scattering and has a significant nonlinear effect on total frictional force. Incommensurate contact does not always give rise to superlubricity: the net effect of two competing interaction mechanisms shown by longitudinal and transverse phonons decides the role of commensurability. Capping of the core has no effect on acoustic phonons but destroys the coherence of transverse optical phonons and creates diffusive scattering. In contrast, the twisting and radial breathing phonon modes have perfect transmission at all energies and can be deemed as the enablers of ultralow friction in CNT oscillators. Our work suggests that tuning of interface geometries can give rise to desirable friction properties in nanoscale devices.

Inverse Edelstein effect induced by magnon-phonon coupling

NASA Astrophysics Data System (ADS)

Xu, Mingran; Puebla, Jorge; Auvray, Florent; Rana, Bivas; Kondou, Kouta; Otani, Yoshichika

2018-05-01

We demonstrate a spin to charge current conversion via magnon-phonon coupling and an inverse Edelstein effect on the hybrid device Ni/Cu (Ag )/Bi 2O3 . The generation of spin current (Js≈108A/m2 ) due to magnon-phonon coupling reveals the viability of acoustic spin pumping as a mechanism for the development of spintronic devices. A full in-plane magnetic field angle dependence of the power absorption and a combination of longitudinal and transverse voltage detection reveals the symmetric and asymmetric components of the inverse Edelstein effect voltage induced by Rayleigh-type surface acoustic waves. While the symmetric components are well studied, asymmetric components still need to be explored. We assign the asymmetric contributions to the interference between longitudinal and shear waves and an anisotropic charge distribution in our hybrid device.

JAPE 91: Influence of terrain masking of the acoustic propagation of helicopter noise

NASA Technical Reports Server (NTRS)

Naz, P.

1993-01-01

The acoustic propagation in the case of a noise source masked by a small element of terrain has been investigated experimentally. These data have been measured during the 'terrain masking' experiment of the NATO JAPE 91 experimental campaign. The main objective of that experiment was to study the acoustic detection of a helicopter masked by a small hill. Microphones have been placed at different locations on the shadow zone of the hill to study the effect of the terrain obstruction on sound propagation. The results presented come from data measured by Atlas Elektronik and by ISL, and have been processed together. The terrain obstruction causes an excess attenuation of the SPL (Sound Pressure Level) for all the frequencies, but this attenuation is more effective for the high frequencies than for the low frequencies. Results typical of diffraction phenomena have been observed; the SPL is minimal at the foot of the hill and is relatively constant beyond it.

Elastic parabolic equation and normal mode solutions for seismo-acoustic propagation in underwater environments with ice covers.

PubMed

Collis, Jon M; Frank, Scott D; Metzler, Adam M; Preston, Kimberly S

2016-05-01

Sound propagation predictions for ice-covered ocean acoustic environments do not match observational data: received levels in nature are less than expected, suggesting that the effects of the ice are substantial. Effects due to elasticity in overlying ice can be significant enough that low-shear approximations, such as effective complex density treatments, may not be appropriate. Building on recent elastic seafloor modeling developments, a range-dependent parabolic equation solution that treats the ice as an elastic medium is presented. The solution is benchmarked against a derived elastic normal mode solution for range-independent underwater acoustic propagation. Results from both solutions accurately predict plate flexural modes that propagate in the ice layer, as well as Scholte interface waves that propagate at the boundary between the water and the seafloor. The parabolic equation solution is used to model a scenario with range-dependent ice thickness and a water sound speed profile similar to those observed during the 2009 Ice Exercise (ICEX) in the Beaufort Sea.

Edge waves and resonances in two-dimensional phononic crystal plates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Jin-Chen, E-mail: hsujc@yuntech.edu.tw; Hsu, Chih-Hsun

2015-05-07

We present a numerical study on phononic band gaps and resonances occurring at the edge of a semi-infinite two-dimensional (2D) phononic crystal plate. The edge supports localized edge waves coupling to evanescent phononic plate modes that decay exponentially into the semi-infinite phononic crystal plate. The band-gap range and the number of edge-wave eigenmodes can be tailored by tuning the distance between the edge and the semi-infinite 2D phononic lattice. As a result, a phononic band gap for simultaneous edge waves and plate waves is created, and phononic cavities beside the edge can be built to support high-frequency edge resonances. Wemore » design an L3 edge cavity and analyze its resonance characteristics. Based on the band gap, high quality factor and strong confinement of resonant edge modes are achieved. The results enable enhanced control over acoustic energy flow in phononic crystal plates, which can be used in designing micro and nanoscale resonant devices and coupling of edge resonances to other types of phononic or photonic crystal cavities.« less

Band structures in two-dimensional phononic crystals with periodic Jerusalem cross slot

NASA Astrophysics Data System (ADS)

Li, Yinggang; Chen, Tianning; Wang, Xiaopeng; Yu, Kunpeng; Song, Ruifang

2015-01-01

In this paper, a novel two-dimensional phononic crystal composed of periodic Jerusalem cross slot in air matrix with a square lattice is presented. The dispersion relations and the transmission coefficient spectra are calculated by using the finite element method based on the Bloch theorem. The formation mechanisms of the band gaps are analyzed based on the acoustic mode analysis. Numerical results show that the proposed phononic crystal structure can yield large band gaps in the low-frequency range. The formation mechanism of opening the acoustic band gaps is mainly attributed to the resonance modes of the cavities inside the Jerusalem cross slot structure. Furthermore, the effects of the geometrical parameters on the band gaps are further explored numerically. Results show that the band gaps can be modulated in an extremely large frequency range by the geometry parameters such as the slot length and width. These properties of acoustic waves in the proposed phononic crystals can potentially be applied to optimize band gaps and generate low-frequency filters and waveguides.

Anharmonic phonon decay in cubic GaN

NASA Astrophysics Data System (ADS)

Cuscó, R.; Domènech-Amador, N.; Novikov, S.; Foxon, C. T.; Artús, L.

2015-08-01

We present a Raman-scattering study of optical phonons in zinc-blende (cubic) GaN for temperatures ranging from 80 to 750 K. The experiments were performed on high-quality, cubic GaN films grown by molecular-beam epitaxy on GaAs (001) substrates. The observed temperature dependence of the optical phonon frequencies and linewidths is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional-theory calculations. The longitudinal-optical (LO) mode relaxation is found to occur via asymmetric decay into acoustic phonons, with an appreciable contribution of higher-order processes. The transverse-optical mode linewidth shows a weak temperature dependence and its frequency downshift is primarily determined by the lattice thermal expansion. The LO phonon lifetime is derived from the observed Raman linewidth and an excellent agreement with previous theoretical predictions is found.

Berry Curvature in Magnon-Phonon Hybrid Systems.

PubMed

Takahashi, Ryuji; Nagaosa, Naoto

2016-11-18

We study theoretically the Berry curvature of the magnon induced by the hybridization with the acoustic phonons via the spin-orbit and dipolar interactions. We first discuss the magnon-phonon hybridization via the dipolar interaction, and show that the dispersions have gapless points in momentum space, some of which form a loop. Next, when both spin-orbit and dipolar interactions are considered, we show anisotropic texture of the Berry curvature and its divergence with and without gap closing. Realistic evaluation of the consequent anomalous velocity is given for yttrium iron garnet.

A general radiation model for sound fields and nearfield acoustical holography in wedge propagation spaces.

PubMed

Hoffmann, Falk-Martin; Fazi, Filippo Maria; Williams, Earl G; Fontana, Simone

2017-09-01

In this work an expression for the solution of the Helmholtz equation for wedge spaces is derived. Such propagation spaces represent scenarios for many acoustical problems where a free field assumption is not eligible. The proposed sound field model is derived from the general solution of the wave equation in cylindrical coordinates, using sets of orthonormal basis functions. The latter are modified to satisfy several boundary conditions representing the reflective behaviour of wedge-shaped propagation spaces. This formulation is then used in the context of nearfield acoustical holography (NAH) and to obtain the expression of the Neumann Green function. The model and its suitability for NAH is demonstrated through both numerical simulations and measured data, where the latter was acquired for the specific case of a loudspeaker on a hemi-cylindrical rigid baffle.

Propagation and head-on collisions of ion-acoustic solitons in a Thomas-Fermi magnetoplasma: Relativistic degeneracy effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akbari-Moghanjoughi, M.

Small amplitude propagation and quasielastic head-on collision of ion-acoustic solitary waves (IASWs) are investigated in a degenerate Thomas-Fermi electron-positron-ion magnetized plasma using extended Poincare-Lighthill-Kuo reductive perturbation method for both ultrarelativistic and nonrelativistic electron/positron degeneracy cases. It is observed that both bright- and dark-type solitary shapes can exist in such plasma, depending on two critical values. The shape of ion-acoustic solitary structures as well as sign of their collision phase shifts are both determined by the same critical values. It is further revealed that relativistic degeneracy of electrons/positrons has significant effect on the propagation as well as interaction of IASWs.

Acoustic Wave Propagation in Snow Based on a Biot-Type Porous Model

NASA Astrophysics Data System (ADS)

Sidler, R.

2014-12-01

Despite the fact that acoustic methods are inexpensive, robust and simple, the application of seismic waves to snow has been sparse. This might be due to the strong attenuation inherent to snow that prevents large scale seismic applications or due to the somewhat counterintuitive acoustic behavior of snow as a porous material. Such materials support a second kind of compressional wave that can be measured in fresh snow and which has a decreasing wave velocity with increasing density of snow. To investigate wave propagation in snow we construct a Biot-type porous model of snow as a function of porosity based on the assumptions that the solid frame is build of ice, the pore space is filled with a mix of air, or air and water, and empirical relationships for the tortuosity, the permeability, the bulk, and the shear modulus.We use this reduced model to investigate compressional and shear wave velocities of snow as a function of porosity and to asses the consequences of liquid water in the snowpack on acoustic wave propagation by solving Biot's differential equations with plain wave solutions. We find that the fast compressional wave velocity increases significantly with increasing density, but also that the fast compressional wave velocity might be even lower than the slow compressional wave velocity for very light snow. By using compressional and shear strength criteria and solving Biot's differential equations with a pseudo-spectral approach we evaluate snow failure due to acoustic waves in a heterogeneous snowpack, which we think is an important mechanism in triggering avalanches by explosives as well as by skiers. Finally, we developed a low cost seismic acquisition device to assess the theoretically obtained wave velocities in the field and to explore the possibility of an inexpensive tool to remotely gather snow water equivalent.

Nano-optomechanical system based on microwave frequency surface acoustic waves

NASA Astrophysics Data System (ADS)

Tadesse, Semere Ayalew

Cavity optomechnics studies the interaction of cavity confined photons with mechanical motion. The emergence of sophisticated nanofabrication technology has led to experimental demonstrations of a wide range of novel optomechanical systems that exhibit strong optomechanical coupling and allow exploration of interesting physical phenomena. Many of the studies reported so far are focused on interaction of photons with localized mechanical modes. For my doctoral research, I did experimental investigations to extend this study to propagating phonons. I used surface travelling acoustic waves as the mechanical element of my optomechanical system. The optical cavities constitute an optical racetrack resonator and photonic crystal nanocavity. This dissertation discusses implementation of this surface acoustic wave based optomechanical system and experimental demonstrations of important consequences of the optomechanical coupling. The discussion focuses on three important achievements of the research. First, microwave frequency surface acoustic wave transducers were co-integrated with an optical racetrack resonator on a piezoelectric aluminum nitride film deposited on an oxidized silicon substrate. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength was achieved. The phase and modal matching conditions in this paradigm were investigated for efficient optmechanical coupling. Second, the optomechanical coupling was pushed further into the sideband resolved regime by integrating the high frequency surface acoustic wave transducers with a photonic crystal nanocavity. This device was used to demonstrate optomecahnically induced transparency and absorption, one of the interesting consequences of cavity optomechanics. Phase coherent interaction of the acoustic wave with multiple nanocavities was also explored. In a related experiment, the photonic crystal nanoscavity was placed inside an acoustic

A k-space method for acoustic propagation using coupled first-order equations in three dimensions.

PubMed

Tillett, Jason C; Daoud, Mohammad I; Lacefield, James C; Waag, Robert C

2009-09-01

A previously described two-dimensional k-space method for large-scale calculation of acoustic wave propagation in tissues is extended to three dimensions. The three-dimensional method contains all of the two-dimensional method features that allow accurate and stable calculation of propagation. These features are spectral calculation of spatial derivatives, temporal correction that produces exact propagation in a homogeneous medium, staggered spatial and temporal grids, and a perfectly matched boundary layer. Spectral evaluation of spatial derivatives is accomplished using a fast Fourier transform in three dimensions. This computational bottleneck requires all-to-all communication; execution time in a parallel implementation is therefore sensitive to node interconnect latency and bandwidth. Accuracy of the three-dimensional method is evaluated through comparisons with exact solutions for media having spherical inhomogeneities. Large-scale calculations in three dimensions were performed by distributing the nearly 50 variables per voxel that are used to implement the method over a cluster of computers. Two computer clusters used to evaluate method accuracy are compared. Comparisons of k-space calculations with exact methods including absorption highlight the need to model accurately the medium dispersion relationships, especially in large-scale media. Accurately modeled media allow the k-space method to calculate acoustic propagation in tissues over hundreds of wavelengths.

Reliability of Raman measurements of thermal conductivity of single-layer graphene due to selective electron-phonon coupling: A first-principles study

NASA Astrophysics Data System (ADS)

Vallabhaneni, Ajit K.; Singh, Dhruv; Bao, Hua; Murthy, Jayathi; Ruan, Xiulin

2016-03-01

Raman spectroscopy has been widely used to measure thermal conductivity (κ ) of two-dimensional (2D) materials such as graphene. This method is based on a well-accepted assumption that different phonon polarizations are in near thermal equilibrium. However, in this paper, we show that, in laser-irradiated single-layer graphene, different phonon polarizations are in strong nonequilibrium, using predictive simulations based on first principles density functional perturbation theory and a multitemperature model. We first calculate the electron cooling rate due to phonon scattering as a function of the electron and phonon temperatures, and the results clearly illustrate that optical phonons dominate the hot electron relaxation process. We then use these results in conjunction with the phonon scattering rates computed using perturbation theory to develop a multitemperature model and resolve the spatial temperature distributions of the energy carriers in graphene under steady-state laser irradiation. Our results show that electrons, optical phonons, and acoustic phonons are in strong nonequilibrium, with the flexural acoustic (ZA) phonons showing the largest nonequilibrium to other phonon modes, mainly due to their weak coupling to other carriers in suspended graphene. Since ZA phonons are the main heat carriers in graphene, we estimate that neglecting this nonequilibrium leads to underestimation of thermal conductivity in experiments at room temperature by a factor of 1.35 to 2.6, depending on experimental conditions and assumptions used. Underestimation is also expected in Raman measurements of other 2D materials when the optical-acoustic phonon coupling is weak.

Inter-Annual Variability of the Acoustic Propagation in the Mediterranean Sea Identified from a Synoptic Monthly Gridded Database as Compared with GDEM

DTIC Science & Technology

2016-12-01

VARIABILITY OF THE ACOUSTIC PROPAGATION IN THE MEDITERRANEAN SEA IDENTIFIED FROM A SYNOPTIC MONTHLY GRIDDED DATABASE AS COMPARED WITH GDEM by...ANNUAL VARIABILITY OF THE ACOUSTIC PROPAGATION IN THE MEDITERRANEAN SEA IDENTIFIED FROM A SYNOPTIC MONTHLY GRIDDED DATABASE AS COMPARED WITH GDEM 5...profiles obtained from the synoptic monthly gridded World Ocean Database (SMD-WOD) and Generalized Digital Environmental Model (GDEM) temperature (T

Deep seafloor arrivals: an unexplained set of arrivals in long-range ocean acoustic propagation.

PubMed

Stephen, Ralph A; Bolmer, S Thompson; Dzieciuch, Matthew A; Worcester, Peter F; Andrew, Rex K; Buck, Linda J; Mercer, James A; Colosi, John A; Howe, Bruce M

2009-08-01

Receptions, from a ship-suspended source (in the band 50-100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), "deep seafloor arrivals," that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation.

PubMed

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-03-11

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation

PubMed Central

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-01-01

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL. PMID:26978361

Phonon-Driven Oscillatory Plasmonic Excitonic Nanomaterials

DOE PAGES

Kirschner, Matthew S.; Ding, Wendu; Li, Yuxiu; ...

2017-12-01

In this study, we demonstrate that coherent acoustic phonons derived from plasmonic nanoparticles can modulate electronic interactions with proximal excitonic molecular species. A series of gold bipyramids with systematically varied aspect ratios and corresponding localized surface plasmon resonance energies, functionalized with a J-aggregated thiacarbocyanine dye molecule, produce two hybridized states that exhibit clear anti-crossing behavior with a Rabi splitting energy of 120 meV. In metal nanoparticles, photoexcitation generates coherent acoustic phonons that cause oscillations in the plasmon resonance energy. In the coupled system, these photo-generated oscillations alter the metal nanoparticle’s energetic contribution to the hybridized system and, as a result,more » change the coupling between the plasmon and exciton. We demonstrate that such modulations in the hybridization is consistent across a wide range of bipyramid ensembles. We also use Finite-Difference Time Domain calculations to develop a simple model describing this behavior. Lastly, such oscillatory plasmonic-excitonic nanomaterials (OPENs) offer a route to manipulate and dynamically-tune the interactions of plasmonic/excitonic systems and unlock a range of potential applications.« less

Negative refraction imaging of acoustic metamaterial lens in the supersonic range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Jianning; Wen, Tingdun; Key Laboratory of Electronic Testing Technology, North University of China, Taiyuan 030051

2014-05-15

Acoustic metamaterials with negative refraction index is the most promising method to overcome the diffraction limit of acoustic imaging to achieve ultrahigh resolution. In this paper, we use localized resonant phononic crystal as the unit cell to construct the acoustic negative refraction lens. Based on the vibration model of the phononic crystal, negative quality parameters of the lens are obtained while excited near the system resonance frequency. Simulation results show that negative refraction of the acoustic lens can be achieved when a sound wave transmiting through the phononic crystal plate. The patterns of the imaging field agree well with thatmore » of the incident wave, while the dispersion is very weak. The unit cell size in the simulation is 0.0005 m and the wavelength of the sound source is 0.02 m, from which we show that acoustic signal can be manipulated through structures with dimensions much smaller than the wavelength of incident wave.« less

Phonon response of some heavy Fermion systems in dynamic limit

NASA Astrophysics Data System (ADS)

Sahoo, Jitendra; Shadangi, Namita; Nayak, Pratibindhya

2017-05-01

The phonon excitation spectrum of some Heavy Fermion (HF) systems in the presence of electron-phonon interaction is studied in the dynamic limit (ω≠0). The renormalized excitation phonon frequencies (ω˜ = ω/ω0) are evaluated through Periodic Anderson Model (PAM) in the presence of electron-phonon interaction using Zubarev-type double time temperature-dependent Green function. The calculated renormalized phonon energy is analyzed through the plots of (ω˜ = ω/ω0) against temperature for different system parameters like effective coupling strength ‘g’ and the position of f-level ‘d’. The observed behavior is analyzed and found to agree with the general features of HF systems found in experiments. Further, it is observed that in finite but small q-values the propagating phonons harden and change to localized peaks.

Electron–phonon coupling in hybrid lead halide perovskites

PubMed Central

Wright, Adam D.; Verdi, Carla; Milot, Rebecca L.; Eperon, Giles E.; Pérez-Osorio, Miguel A.; Snaith, Henry J.; Giustino, Feliciano; Johnston, Michael B.; Herz, Laura M.

2016-01-01

Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron–phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites. PMID:27225329

Multi-channel unidirectional transmission of phononic crystal heterojunctions

NASA Astrophysics Data System (ADS)

Xu, Zhenlong; Tong, Jie; Wu, Fugen

2018-02-01

Two square steel columns are arranged in air to form two-dimensional square lattice phononic crystals (PNCs). Two PNCs can be combined into a non-orthogonal 45∘ heterojunction when the difference in the directional band gaps of the two PNC types is utilized. The finite element method is used to calculate the acoustic band structure, the heterogeneous junction transmission characteristics, acoustic field distribution, and many others. Results show that a non-orthogonal PNC heterojunction can produce a multi-channel unidirectional transmission of acoustic waves. With the square scatterer rotated, the heterojunction can select a frequency band for unidirectional transmission performance. This capability is particularly useful for constructing acoustic diodes with wide-bands and high-efficiency unidirectional transmission characteristics.

Lightning characterization through acoustic and electromagnetic measurements recorded during the HyMeX SOP1 and simulation of the acoustic nonlinear propagation in realistic thunderstorm meteorological conditions

NASA Astrophysics Data System (ADS)

Gallin, L.; Coulouvrat, F.; Farges, T.; Marchiano, R.; Defer, E.; Rison, W.; Schulz, W.; Nuret, M.

2013-12-01

The goal is to study the transformation of the thunder (amplitude, spectrum) during its travel from the lightning channel towards a detector (microphone, microbarometer), considering propagation distances of less than 50 km and complex local meteorological properties. Inside the European HyMeX project, the SOP1 campaign (2012) took place from September 2012 to November 2012 in South of France. An acoustic station (center: 4.39° E, 44.08° N) composed of a microphone array placed inside a microbarometer array was installed by CEA near city of Uzès. It was located in the center of an LMA network coming with two slow antennas. This network was deployed in France for the first time by the New Mexico Tech and LERMA laboratory. The detections from the European lightning location system EUCLID complete this dataset. During the SOP1 period several storms passed over the station. The post-processings of the records point out days with interesting thunderstorms. Especially during the 26th of October 2012 in the evening (around 8 pm) a thunderstorm passed just over the acoustic station. Not too many lightning strokes are detected by EUCLID, the corresponding flashes are then well characterized by the LMA network. Slow antennas present good electric field measurements. The acoustic records have excellent quality. We present for some selected flashes a comparative study of the different measurements (LMA, slow antenna, EUCLID, microphones, microbarometers): focusing on amplitude and spectrum of the thunder waveforms, and on propagation effects due to the meteorological conditions. To quantify the impact of these meteorological conditions on the propagating thunder (from the lightning sources to the acoustic array), a code named Flhoward is used [Dagrau et al., J. Acoust. Soc. Am., 130, 20-32, 2011][Coulouvrat, Wave Motion, 49, 50--63, 2012]. It is designed to simulate the nonlinear propagation of acoustic shock waves through a realistic atmosphere model (including temperature

Size-Dependent Coherent-Phonon Plasmon Modulation and Deformation Characterization in Gold Bipyramids and Nanojavelins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirschner, Matthew S.; Lethiec, Clotilde M.; Lin, Xiao-Min

2016-04-04

Localized surface plasmon resonances (LSPRs) arising from metallic nanoparticles offer an array of prospective applications that range from chemical sensing to biotherapies. Bipyramidal particles exhibit particularly narrow ensemble LSPR resonances that reflect small dispersity of size and shape but until recently were only synthetically accessible over a limited range of sizes with corresponding aspect ratios. Narrow size dispersion offers the opportunity to examine ensemble dynamical phenomena such as coherent phonons that induce periodic oscillations of the LSPR energy. Here, we characterize transient optical behavior of a large range of gold bipyramid sizes, as well as higher aspect ratio nanojavelin ensemblesmore » with specific attention to the lowest-order acoustic phonon mode of these nanoparticles. We report coherent phonon-driven oscillations of the LSPR position for particles with resonances spanning 670 to 1330 nm. Nanojavelins were shown to behave similarly to bipyramids but offer the prospect of separate control over LSPR energy and coherent phonon oscillation period. We develop a new methodology for quantitatively measuring mechanical expansion caused by photogenerated coherent phonons. Using this method, we find an elongation of approximately 1% per photon absorbed per unit cell and that particle expansion along the lowest frequency acoustic phonon mode is linearly proportional to excitation fluence for the fluence range studied. These characterizations provide insight regarding means to manipulate phonon period and transient mechanical deformation.« less

Modeling the propagation of nonlinear three-dimensional acoustic beams in inhomogeneous media.

PubMed

Jing, Yuan; Cleveland, Robin O

2007-09-01

A three-dimensional model of the forward propagation of nonlinear sound beams in inhomogeneous media, a generalized Khokhlov-Zabolotskaya-Kuznetsov equation, is described. The Texas time-domain code (which accounts for paraxial diffraction, nonlinearity, thermoviscous absorption, and absorption and dispersion associated with multiple relaxation processes) was extended to solve for the propagation of nonlinear beams for the case where all medium properties vary in space. The code was validated with measurements of the nonlinear acoustic field generated by a phased array transducer operating at 2.5 MHz in water. A nonuniform layer of gel was employed to create an inhomogeneous medium. There was good agreement between the code and measurements in capturing the shift in the pressure distribution of both the fundamental and second harmonic due to the gel layer. The results indicate that the numerical tool described here is appropriate for propagation of nonlinear sound beams through weakly inhomogeneous media.

Acoustically trapped colloidal crystals that are reconfigurable in real time

PubMed Central

Caleap, Mihai; Drinkwater, Bruce W.

2014-01-01

Photonic and phononic crystals are metamaterials with repeating unit cells that result in internal resonances leading to a range of wave guiding and filtering properties and are opening up new applications such as hyperlenses and superabsorbers. Here we show the first, to our knowledge, 3D colloidal phononic crystal that is reconfigurable in real time and demonstrate its ability to rapidly alter its frequency filtering characteristics. Our reconfigurable material is assembled from microspheres in aqueous solution, trapped with acoustic radiation forces. The acoustic radiation force is governed by an energy landscape, determined by an applied high-amplitude acoustic standing wave field, in which particles move swiftly to energy minima. This creates a colloidal crystal of several milliliters in volume with spheres arranged in an orthorhombic lattice in which the acoustic wavelength is used to control the lattice spacing. Transmission acoustic spectroscopy shows that the new colloidal crystal behaves as a phononic metamaterial and exhibits clear band-pass and band-stop frequencies which are adjusted in real time. PMID:24706925

Time Resolved X-Ray Diffraction Study of Acoustoelectrically Amplified Phonons.

NASA Astrophysics Data System (ADS)

Chapman, Leroy Dean

X-rays diffracted by nearly perfect crystals of n-type InSb have been investigated in the presence of intense acoustoelectrically (A.E.) amplified phonons. The fact that these phonons are nearly monochromatic and have a well defined propagation and polarization direction presents an excellent opportunity to investigate the nature of x -ray photon-phonon scattering in a diffracting crystal. The Debye-Waller factor which accounts for the attenuation of diffracted x-ray intensities due to thermal phonons is reflection dependent owing to its sin (theta)/(lamda) dependence. We have performed experiments comparing the (004) and (008) anomalously transmitted intensities as a function of A.E. amplified flux. The attenuation of both reflections due to the amplified phonons was the same in direct contradiction to an expected sin (theta)/(lamda) dependence. Some possible reasons for this failure are discussed. In a Bragg reflection scattering geometry, the intense monochromatic amplified phonons give rise to satellite peaks symmetrically located about the central elastic Brag peak in a rocking profile. We report in this thesis on the first observation of satellites in a thin crystal Laue transmission geometry. We have theoretically simulated the rocking profiles with some success. The A.E. amplification process in InSb is strongly favored for {110} propagation fast transverse (FT) phonons. In earlier experiments it was found that non-{110} FT phonons were also produced during the amplification process. We have developed a time resolved x-ray counting system which, in conjunction with a spatially resolved x-ray beam and a localized, traveling A.E. phonon distribution, allow the time evolution of the amplified distribution to be followed. We report on time resolved measurements for both the symmetric Bragg and Laue geometries from which we can determine when and where non-{110 } FT flux is generated and restrict the possible mechanisms for its generation.

Sonar Performance Estimation Model with Seismo-Acoustic Effects on Underwater Sound Propagation

DTIC Science & Technology

1989-06-27

properties of 12 the bottom sediments. The ray theory is highly satisfactory to predict and explain some electromagnetic phenomena, and it is very useful in...erroneous transmission loss computations where acoustic interference occurs. However, his transmission loss calculations are made using ray theory which is...developed which treat some of these properties. Each model has its virtues and limitations. For high- frequency sound propagation the ray theory can

Ultrafast dynamics of quasiparticles and coherent acoustic phonons in slightly underdoped (BaK)Fe2As2

PubMed Central

Lin, Kung-Hsuan; Wang, Kuan-Jen; Chang, Chung-Chieh; Wen, Yu-Chieh; Lv, Bing; Chu, Ching-Wu; Wu, Maw-Kuen

2016-01-01

We have utilized ultrafast optical spectroscopy to study carrier dynamics in slightly underdoped (BaK)Fe2As2 crystals without magnetic transition. The photoelastic signals due to coherent acoustic phonons have been quantitatively investigated. According to our temperature-dependent results, we found that the relaxation component of superconducting quasiparticles persisted from the superconducting state up to at least 70 K in the normal state. Our findings suggest that the pseudogaplike feature in the normal state is possibly the precursor of superconductivity. We also highlight that the pseudogap feature of K-doped BaFe2As2 is different from that of other iron-based superconductors, including Co-doped or P-doped BaFe2As2. PMID:27180873

Multi-band asymmetric acoustic transmission in a bended waveguide with multiple mechanisms

NASA Astrophysics Data System (ADS)

Huang, Yu-lei; Sun, Hong-xiang; Xia, Jian-ping; Yuan, Shou-qi; Ding, Xin-lei

2016-07-01

We report the realization of a multi-band device of the asymmetric acoustic transmission by placing a phononic crystal inside a bended waveguide immersed in water, as determined both experimentally and numerically. The asymmetric acoustic transmission exists in three frequency bands below 500 kHz induced by multiple mechanisms. Besides the band gap of the phononic crystal, we also introduce the deaf mode and interaction between the phononic crystal and waveguide. More importantly, this asymmetric transmission can be systematically controlled by mechanically rotating the square rods of the phononic crystal. The device has the advantages of multiple band, broader bandwidth, and adjustable property, showing promising applications in ultrasonic devices.

Orbitally-driven giant phonon anharmonicity in SnSe

DOE PAGES

Li, Chen W.; Hong, Jiawang; May, Andrew F.; ...

2015-10-19

We understand that elementary excitations and their couplings in condensed matter systems is critical to develop better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The material with the current record for thermoelectric conversion efficiency, SnSe, achieves an ultra-low thermal conductivity, but the mechanism enabling this strong phonon scattering remains largely unknown. Using inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and revealed the origin of ionic-potential anharmonicity responsible for the unique properties of SnSe. Wemore » show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelectric-like lattice instability. Our results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers precious insights on how electron-phonon and phononphonon interactions may lead to the realization of ultra-low thermal conductivity.« less

Orbitally driven giant phonon anharmonicity in SnSe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, C. W.; Hong, J.; May, A. F.

Understanding elementary excitations and their couplings in condensed matter systems is critical for developing better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The current record material for thermoelectric conversion efficiency, SnSe, has an ultralow thermal conductivity, but the mechanism behind the strong phonon scattering remains largely unknown. From inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and found the origin of the ionic-potential anharmonicity responsible for the unique properties of SnSe. We show that themore » giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelectric-like lattice instability. The present results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers new insights on how electron–phonon and phonon–phonon interactions may lead to the realization of ultralow thermal conductivity.« less

Anharmonic phonon-polariton dynamics in ferroelectric LiNbO3 studied with single-shot pump-probe imaging spectroscopy

NASA Astrophysics Data System (ADS)

Kuribayashi, T.; Motoyama, T.; Arashida, Y.; Katayama, I.; Takeda, J.

2018-05-01

We demonstrate that single-shot pump-probe imaging spectroscopy with an echelon mirror enables us to disclose the ferroelectric phonon-polariton dynamics across a wide temperature range from 10 K to 375 K while avoiding the photorefractive effects that appear prominently at low temperatures. The E-mode phonon-polaritons corresponding to the two transverse optical modes, TO1 and TO3, up to ˜7 THz were induced in LiNbO3 through an impulsive stimulated Raman scattering process. Subsequently, using single-shot pump-probe imaging spectroscopy over a minimal cumulative time, we successfully visualized the phonon-polariton dynamics in time-wavelength space even at low temperatures. We found that the phase-matching condition significantly affected the observed temperature-dependent phonon-polariton frequency shift. The anharmonicity of the TO1 and TO3 modes was then evaluated based on an anharmonic model involving higher-order interactions with acoustic phonons while eliminating the influence of the frequency shift due to the phase-matching condition. The observed wavenumber-dependent damping rate was analyzed by considering the bilinear coupling of the TO1 or TO3 modes with the thermally activated relaxation mode. We found that the phonon-polariton with a higher frequency and wavenumber had a higher damping rate at high temperatures because of its frequent interaction with the thermally activated relaxation mode and acoustic phonons. The TO3 mode displayed greater bilinear coupling than the TO1 mode, which may also have contributed to the observed high damping rate. Thus, using our unique single-shot spectroscopy technique, we could reveal the overall anharmonic characteristics of the E-mode phonon-polaritons arising from both the acoustic phonons and the relaxation mode.

Heavy-impurity resonance, hybridization, and phonon spectral functions in Fe 1-xM xSi, M=Ir,Os

DOE PAGES

Delaire, O.; Al-Qasir, Iyad I.; May, Andrew F.; ...

2015-03-31

The vibrational behavior of heavy substitutional impurities (M=Ir,Os) in Fe 1-xM xSi (x = 0, 0.02, 0.04, 0.1) was investigated with a combination of inelastic neutron scattering (INS), transport measurements, and first-principles simulations. In this paper, our INS measurements on single-crystals mapped the four-dimensional dynamical structure factor, S(Q;E), for several compositions and temperatures. Our results show that both Ir and Os impurities lead to the formation of a weakly dispersive resonance vibrational mode, in the energy range of the acoustic phonon dispersions of the FeSi host. We also show that Ir doping, which introduces free carriers and increases electron-phonon coupling,more » leads to softened interatomic force-constants compared to doping with Os, which is isoelectronic to Fe. We analyze the phonon S(Q,E) from INS through a Green's function model incorporating the phonon self-energy based on first-principles density functional theory (DFT) simulations. Calculations of the quasiparticle spectral functions in the doped system reveal the hybridization between the resonance and the acoustic phonon modes. Finally, our results demonstrate a strong interaction of the host acoustic dispersions with the resonance mode, likely leading to the large observed suppression in lattice thermal conductivity.« less

Acoustic structure and propagation in highly porous, layered, fibrous materials

NASA Technical Reports Server (NTRS)

Lambert, R. F.; Tesar, J. S.

1984-01-01

The acoustic structure and propagation of sound in highly porous, layered, fine fiber materials is examined. Of particular interest is the utilization of the Kozeny number for determining the static flow resistance and the static structure factor based on flow permeability measurements. In this formulation the Kozeny number is a numerical constant independent of volume porosity at high porosities. The other essential parameters are then evaluated employing techniques developed earlier for open cell foams. The attenuation and progressive phase characteristics in bulk samples are measured and compared with predicted values. The agreements on the whole are very satisfactory.

The effect of buildings on acoustic pulse propagation in an urban environment.

PubMed

Albert, Donald G; Liu, Lanbo

2010-03-01

Experimental measurements were conducted using acoustic pulse sources in a full-scale artificial village to investigate the reverberation, scattering, and diffraction produced as acoustic waves interact with buildings. These measurements show that a simple acoustic source pulse is transformed into a complex signature when propagating through this environment, and that diffraction acts as a low-pass filter on the acoustic pulse. Sensors located in non-line-of-sight (NLOS) positions usually recorded lower positive pressure maxima than sensors in line-of-sight positions. Often, the first arrival on a NLOS sensor located around a corner was not the largest arrival, as later reflection arrivals that traveled longer distances without diffraction had higher amplitudes. The waveforms are of such complexity that human listeners have difficulty identifying replays of the signatures generated by a single pulse, and the usual methods of source location based on the direction of arrivals may fail in many cases. Theoretical calculations were performed using a two-dimensional finite difference time domain (FDTD) method and compared to the measurements. The predicted peak positive pressure agreed well with the measured amplitudes for all but two sensor locations directly behind buildings, where the omission of rooftop ray paths caused the discrepancy. The FDTD method also produced good agreement with many of the measured waveform characteristics.

High-speed asynchronous optical sampling for high-sensitivity detection of coherent phonons

NASA Astrophysics Data System (ADS)

Dekorsy, T.; Taubert, R.; Hudert, F.; Schrenk, G.; Bartels, A.; Cerna, R.; Kotaidis, V.; Plech, A.; Köhler, K.; Schmitz, J.; Wagner, J.

2007-12-01

A new optical pump-probe technique is implemented for the investigation of coherent acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond lasers. Asynchronous optical sampling (ASOPS) provides the performance of on all-optical oscilloscope and allows us to record optically induced lattice dynamics over nanosecond times with femtosecond resolution at scan rates of 10 kHz without any moving part in the set-up. Within 1 minute of data acquisition time signal-to-noise ratios better than 107 are achieved. We present examples of the high-sensitivity detection of coherent phonons in superlattices and of the coherent acoustic vibration of metallic nanoparticles.

Analog model for quantum gravity effects: phonons in random fluids.

PubMed

Krein, G; Menezes, G; Svaiter, N F

2010-09-24

We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model.

Root finding in the complex plane for seismo-acoustic propagation scenarios with Green's function solutions.

PubMed

McCollom, Brittany A; Collis, Jon M

2014-09-01

A normal mode solution to the ocean acoustic problem of the Pekeris waveguide with an elastic bottom using a Green's function formulation for a compressional wave point source is considered. Analytic solutions to these types of waveguide propagation problems are strongly dependent on the eigenvalues of the problem; these eigenvalues represent horizontal wavenumbers, corresponding to propagating modes of energy. The eigenvalues arise as singularities in the inverse Hankel transform integral and are specified by roots to a characteristic equation. These roots manifest themselves as poles in the inverse transform integral and can be both subtle and difficult to determine. Following methods previously developed [S. Ivansson et al., J. Sound Vib. 161 (1993)], a root finding routine has been implemented using the argument principle. Using the roots to the characteristic equation in the Green's function formulation, full-field solutions are calculated for scenarios where an acoustic source lies in either the water column or elastic half space. Solutions are benchmarked against laboratory data and existing numerical solutions.

Spin Seebeck effect and ballistic transport of quasi-acoustic magnons in room-temperature yttrium iron garnet films

NASA Astrophysics Data System (ADS)

Noack, Timo B.; Musiienko-Shmarova, Halyna Yu; Langner, Thomas; Heussner, Frank; Lauer, Viktor; Heinz, Björn; Bozhko, Dmytro A.; Vasyuchka, Vitaliy I.; Pomyalov, Anna; L’vov, Victor S.; Hillebrands, Burkard; Serga, Alexander A.

2018-06-01

We studied the transient behavior of the spin current generated by the longitudinal spin Seebeck effect (LSSE) in a set of platinum-coated yttrium iron garnet (YIG) films of different thicknesses. The LSSE was induced by means of pulsed microwave heating of the Pt layer and the spin currents were measured electrically using the inverse spin Hall effect in the same layer. We demonstrate that the time evolution of the LSSE is determined by the evolution of the thermal gradient triggering the flux of thermal magnons in the vicinity of the YIG/Pt interface. These magnons move ballistically within the YIG film with a constant group velocity, while their number decays exponentially within an effective propagation length. The ballistic flight of the magnons with energies above 20 K is a result of their almost linear dispersion law, similar to that of acoustic phonons. By fitting the time-dependent LSSE signal for different film thicknesses varying by almost an order of magnitude, we found that the effective propagation length is practically independent of the YIG film thickness. We consider this fact as strong support of a ballistic transport scenario—the ballistic propagation of quasi-acoustic magnons in room temperature YIG.

Temperature induced phonon behaviour in germanium selenide thin films probed by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Taube, A.; Łapińska, A.; Judek, J.; Wochtman, N.; Zdrojek, M.

2016-08-01

Here we report a detailed study of temperature-dependent phonon properties of exfoliated germanium selenide thin films (several tens of nanometers thick) probed by Raman spectroscopy in the 70-350 K temperature range. The temperature-dependent behavior of the positions and widths of the Raman modes was nonlinear. We concluded that the observed effects arise from anharmonic phonon-phonon interactions and are explained by the phenomenon of optical phonon decay into acoustic phonons. At temperatures above 200 K, the position of the Raman modes tended to be linearly dependent, and the first order temperature coefficients χ were  -0.0277, -0.0197 and  -0.031 cm-1 K-1 for B 3g , A g(1) and A g(2) modes, respectively.

Propagation characteristics of dust-acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

NASA Astrophysics Data System (ADS)

Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

2016-08-01

The experimental observation of the self-excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion-dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iglesias, J. M.; Martín, M. J.; Pascual, E.

2016-01-25

We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared with considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between 1 and 3 × 10{sup 12 }cm{sup −2}. Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carriermore » cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to the additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density.« less

Numerical emulation of Thru-Reflection-Line calibration for the de-embedding of Surface Acoustic Wave devices.

PubMed

Mencarelli, D; Djafari-Rouhani, B; Pennec, Y; Pitanti, A; Zanotto, S; Stocchi, M; Pierantoni, L

2018-06-18

In this contribution, a rigorous numerical calibration is proposed to characterize the excitation of propagating mechanical waves by interdigitated transducers (IDTs). The transition from IDT terminals to phonon waveguides is modeled by means of a general circuit representation that makes use of Scattering Matrix (SM) formalism. In particular, the three-step calibration approach called the Thru-Reflection-Line (TRL), that is a well-established technique in microwave engineering, has been successfully applied to emulate typical experimental conditions. The proposed procedure is suitable for the synthesis/optimization of surface-acoustic-wave (SAW) based devices: the TRL calibration allows to extract/de-embed the acoustic component, namely resonator or filter, from the outer IDT structure, regardless of complexity and size of the letter. We report, as a result, the hybrid scattering parameters of the IDT transition to a mechanical waveguide formed by a phononic crystal patterned on a piezoelectric AlN membrane, where the effect of a discontinuity from periodic to uniform mechanical waveguide is also characterized. In addition, to ensure the correctness of our numerical calculations, the proposed method has been validated by independent calculations.

Propagation of flexural waves in inhomogeneous plates exhibiting hysteretic nonlinearity: Nonlinear acoustic black holes.

PubMed

Gusev, Vitalyi E; Ni, Chenyin; Lomonosov, Alexey; Shen, Zhonghua

2015-08-01

Theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous material on flexural wave in the plates of continuously varying thickness is developed. For the wedges with thickness increasing as a power law of distance from its edge strong modifications of the wave dynamics with propagation distance are predicted. It is found that nonlinear absorption progressively disappearing with diminishing wave amplitude leads to complete attenuation of acoustic waves in most of the wedges exhibiting black hole phenomenon. It is also demonstrated that black holes exist beyond the geometrical acoustic approximation. Applications include nondestructive evaluation of micro-inhomogeneous materials and vibrations damping. Copyright © 2015 Elsevier B.V. All rights reserved.

Band structures in fractal grading porous phononic crystals

NASA Astrophysics Data System (ADS)

Wang, Kai; Liu, Ying; Liang, Tianshu; Wang, Bin

2018-05-01

In this paper, a new grading porous structure is introduced based on a Sierpinski triangle routine, and wave propagation in this fractal grading porous phononic crystal is investigated. The influences of fractal hierarchy and porosity on the band structures in fractal graidng porous phononic crystals are clarified. Vibration modes of unit cell at absolute band gap edges are given to manifest formation mechanism of absolute band gaps. The results show that absolute band gaps are easy to form in fractal structures comparatively to the normal ones with the same porosity. Structures with higher fractal hierarchies benefit multiple wider absolute band gaps. This work provides useful guidance in design of fractal porous phononic crystals.

SLOW PATCHY EXTREME-ULTRAVIOLET PROPAGATING FRONTS ASSOCIATED WITH FAST CORONAL MAGNETO-ACOUSTIC WAVES IN SOLAR ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Y.; Ding, M. D.; Chen, P. F., E-mail: guoyang@nju.edu.cn

2015-08-15

Using the high spatiotemporal resolution extreme ultraviolet (EUV) observations of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we conduct a statistical study of the observational properties of the coronal EUV propagating fronts. We find that it might be a universal phenomenon for two types of fronts to coexist in a large solar eruptive event. It is consistent with the hybrid model of EUV propagating fronts, which predicts that coronal EUV propagating fronts consist of both a fast magneto-acoustic wave and a nonwave component. We find that the morphologies, propagation behaviors, and kinematic features of the two EUVmore » propagating fronts are completely different from each other. The fast magneto-acoustic wave fronts are almost isotropic. They travel continuously from the flaring region across multiple magnetic polarities to global distances. On the other hand, the slow nonwave fronts appear as anisotropic and sequential patches of EUV brightening. Each patch propagates locally in the magnetic domains where the magnetic field lines connect to the bottom boundary and stops at the magnetic domain boundaries. Within each magnetic domain, the velocities of the slow patchy nonwave component are an order of magnitude lower than that of the fast-wave component. However, the patches of the slow EUV propagating front can jump from one magnetic domain to a remote one. The velocities of such a transit between different magnetic domains are about one-third to one-half of those of the fast-wave component. The results show that the velocities of the nonwave component, both within one magnetic domain and between different magnetic domains, are highly nonuniform due to the inhomogeneity of the magnetic field in the lower atmosphere.« less

Ultra-wide acoustic band gaps in pillar-based phononic crystal strips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coffy, Etienne, E-mail: etienne.coffy@femto-st.fr; Lavergne, Thomas; Addouche, Mahmoud

2015-12-07

An original approach for designing a one dimensional phononic crystal strip with an ultra-wide band gap is presented. The strip consists of periodic pillars erected on a tailored beam, enabling the generation of a band gap that is due to both Bragg scattering and local resonances. The optimized combination of both effects results in the lowering and the widening of the main band gap, ultimately leading to a gap-to-midgap ratio of 138%. The design method used to improve the band gap width is based on the flattening of phononic bands and relies on the study of the modal energy distributionmore » within the unit cell. The computed transmission through a finite number of periods corroborates the dispersion diagram. The strong attenuation, in excess of 150 dB for only five periods, highlights the interest of such ultra-wide band gap phononic crystal strips.« less

Exciton-phonon system on a star graph: A perturbative approach.

PubMed

Yalouz, Saad; Pouthier, Vincent

2016-05-01

Based on the operatorial formulation of the perturbation theory, the properties of an exciton coupled with optical phonons on a star graph are investigated. Within this method, the dynamics is governed by an effective Hamiltonian, which accounts for exciton-phonon entanglement. The exciton is dressed by a virtual phonon cloud whereas the phonons are clothed by virtual excitonic transitions. In spite of the coupling with the phonons, it is shown that the energy spectrum of the dressed exciton resembles that of a bare exciton. The only differences originate in a polaronic mechanism that favors an energy shift and a decay of the exciton hopping constant. By contrast, the motion of the exciton allows the phonons to propagate over the graph so that the dressed normal modes drastically differ from the localized modes associated to bare phonons. They define extended vibrations whose properties depend on the state occupied by the exciton that accompanies the phonons. It is shown that the phonon frequencies, either red shifted or blue shifted, are very sensitive to the model parameter in general, and to the size of the graph in particular.

Bending and splitting of spoof surface acoustic waves through structured rigid surface

NASA Astrophysics Data System (ADS)

Xie, Sujun; Ouyang, Shiliang; He, Zhaojian; Wang, Xiaoyun; Deng, Ke; Zhao, Heping

2018-03-01

In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC), which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect), the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

Landau-Zener-Stückelberg Interferometry in Quantum Dots with Fast Rise Times: Evidence for Coherent Phonon Driving.

PubMed

Korkusinski, M; Studenikin, S A; Aers, G; Granger, G; Kam, A; Sachrajda, A S

2017-02-10

Manipulating qubits via electrical pulses in a piezoelectric material such as GaAs can be expected to generate incidental acoustic phonons. In this Letter we determine theoretically and experimentally the consequences of these phonons for semiconductor spin qubits using Landau-Zener-Stückelberg interferometry. Theoretical calculations predict that phonons in the presence of the spin-orbit interaction produce both phonon-Rabi fringes and accelerated evolution at the singlet-triplet anticrossing. Observed features confirm the influence of these mechanisms. Additionally, evidence is found that the pulsed gates themselves act as phonon cavities increasing the influence of phonons under specific resonant conditions.

Turbofan Duct Propagation Model

NASA Technical Reports Server (NTRS)

Lan, Justin H.; Posey, Joe W. (Technical Monitor)

2001-01-01

The CDUCT code utilizes a parabolic approximation to the convected Helmholtz equation in order to efficiently model acoustic propagation in acoustically treated, complex shaped ducts. The parabolic approximation solves one-way wave propagation with a marching method which neglects backwards reflected waves. The derivation of the parabolic approximation is presented. Several code validation cases are given. An acoustic lining design process for an example aft fan duct is discussed. It is noted that the method can efficiently model realistic three-dimension effects, acoustic lining, and flow within the computational capabilities of a typical computer workstation.

The significance of temperature dependence on the piezoelectric energy harvesting by using a phononic crystal

NASA Astrophysics Data System (ADS)

Aly, Arafa H.; Nagaty, Ahmed; Khalifa, Zaki; Mehaney, Ahmed

2018-05-01

In this study, an acoustic energy harvester based on a two-dimensional phononic crystal has been constructed. The present structure consists of silicon cylinders in the air background with a polyvinylidene fluoride cylinder as a defect to confine the acoustic energy. The presented energy harvester depends on the piezoelectric effect (using the piezoelectric material polyvinylidene fluoride) that converts the confined acoustic energy to electric energy. The maximum output voltage obtained equals 170 mV. Moreover, the results revealed that the output voltage can be increased with increasing temperature. In addition, the effects of the load resistance and the geometry of the piezoelectric material on the output voltage have been studied theoretically. Based on these results, all previous studies about energy harvesting in phononic structures must take temperature effects into account.

Strong magnon-phonon coupling in NaFeAs studied by neutron scattering

NASA Astrophysics Data System (ADS)

Li, Yu; Yamani, Zahra; Song, Yu; Zhang, Chenglin; Dai, Pengcheng

We carried on inelastic neutron scattering experiment on the triple axis spectrometer in CNBC in Chalk River. We measured both the phonon and magnon in NaFeAs single crystals and their temperature dependence. Since structural transition temperature (TS) and the magnetic transition temperature (T N) are well separated in NaFeAs, it provides us an unique chance to exclude the consequence or magnetic order and focus on the so called nematic phase. As the previous paper on BaFe2As2, we observed the strong phonon softening nearby the structural transition temperature at very small q (q<0.1). This makes the phonon in NaFeAs deviate from the classical linear dispersion relationship for acoustic phonons. Besides the phonon softening, we also observe phonon hardening at a larger q range when the temperature goes down. This is accompanied by the stiffening of the magnons which can be represented by the linewidth of the low energy magnetic peaks. Our results suggest that there is strong coupling between the phonons and magnons in NaFeAs.

Phononic thermal conductivity in silicene: the role of vacancy defects and boundary scattering

NASA Astrophysics Data System (ADS)

Barati, M.; Vazifehshenas, T.; Salavati-fard, T.; Farmanbar, M.

2018-04-01

We calculate the thermal conductivity of free-standing silicene using the phonon Boltzmann transport equation within the relaxation time approximation. In this calculation, we investigate the effects of sample size and different scattering mechanisms such as phonon–phonon, phonon-boundary, phonon-isotope and phonon-vacancy defect. We obtain some similar results to earlier works using a different model and provide a more detailed analysis of the phonon conduction behavior and various mode contributions. We show that the dominant contribution to the thermal conductivity of silicene, which originates from the in-plane acoustic branches, is about 70% at room temperature and this contribution becomes larger by considering vacancy defects. Our results indicate that while the thermal conductivity of silicene is significantly suppressed by the vacancy defects, the effect of isotopes on the phononic transport is small. Our calculations demonstrate that by removing only one of every 400 silicon atoms, a substantial reduction of about 58% in thermal conductivity is achieved. Furthermore, we find that the phonon-boundary scattering is important in defectless and small-size silicene samples, especially at low temperatures.

Forward Sound Propagation Around Seamounts: Application of Acoustic Models to the Kermit-Roosevelt and Elvis Seamounts

DTIC Science & Technology

2009-06-01

large number of range steps. Brooke et al. [73] developed a Canadian Parabolic Equation model ( PECan ). In the model, the split-step Padé algorithm... PECan : A Canadian parabolic equation model for underwater sound propagation. J. Computational Acoustics, 9(1):69-100, 2001 [74] Michael D

Designing broad phononic band gaps for in-plane modes

NASA Astrophysics Data System (ADS)

Li, Yang Fan; Meng, Fei; Li, Shuo; Jia, Baohua; Zhou, Shiwei; Huang, Xiaodong

2018-03-01

Phononic crystals are known as artificial materials that can manipulate the propagation of elastic waves, and one essential feature of phononic crystals is the existence of forbidden frequency range of traveling waves called band gaps. In this paper, we have proposed an easy way to design phononic crystals with large in-plane band gaps. We demonstrated that the gap between two arbitrarily appointed bands of in-plane mode can be formed by employing a certain number of solid or hollow circular rods embedded in a matrix material. Topology optimization has been applied to find the best material distributions within the primitive unit cell with maximal band gap width. Our results reveal that the centroids of optimized rods coincide with the point positions generated by Lloyd's algorithm, which deepens our understandings on the formation mechanism of phononic in-plane band gaps.

Dominant phonon polarization conversion across dimensionally mismatched interfaces: Carbon-nanotube-graphene junction

NASA Astrophysics Data System (ADS)

Shi, Jingjing; Lee, Jonghoon; Dong, Yalin; Roy, Ajit; Fisher, Timothy S.; Ruan, Xiulin

2018-04-01

Dimensionally mismatched interfaces are emerging for thermal management applications, but thermal transport physics remains poorly understood. Here we consider the carbon-nanotube-graphene junction, which is a dimensionally mismatched interface between one- and two-dimensional materials and is the building block for carbon-nanotube (CNT)-graphene three-dimensional networks. We predict the transmission function of individual phonon modes using the wave packet method; surprisingly, most incident phonon modes show predominantly polarization conversion behavior. For instance, longitudinal acoustic (LA) polarizations incident from CNTs transmit mainly into flexural transverse (ZA) polarizations in graphene. The frequency stays the same as the incident mode, indicating elastic transmission. Polarization conversion is more significant as the phonon wavelength increases. We attribute such unique phonon polarization conversion behavior to the dimensional mismatch across the interface, and it opens significantly new phonon transport channels as compared to existing theories where polarization conversion is neglected.

Simulation of wave propagation inside a human eye: acoustic eye model (AEM)

NASA Astrophysics Data System (ADS)

Požar, T.; Halilovič, M.; Horvat, D.; Petkovšek, R.

2018-02-01

The design and development of the acoustic eye model (AEM) is reported. The model consists of a computer-based simulation that describes the propagation of mechanical disturbance inside a simplified model of a human eye. The capabilities of the model are illustrated with examples, using different laser-induced initial loading conditions in different geometrical configurations typically occurring in ophthalmic medical procedures. The potential of the AEM is to predict the mechanical response of the treated eye tissue in advance, thus complementing other preliminary procedures preceding medical treatments.

Thermal conductivity in large - J two-dimensional antiferromagnets: Role of phonon scattering

DOE PAGES

Chernyshev, A. L.; Brenig, Wolfram

2015-08-05

Different types of relaxation processes for magnon heat current are discussed, with a particular focus on coupling to three-dimensional phonons. There is thermal conductivity by these in-plane magnetic excitations using two distinct techniques: Boltzmann formalism within the relaxation-time approximation and memory-function approach. Also considered are the scattering of magnons by both acoustic and optical branches of phonons. We demonstrate an accord between the two methods, regarding the asymptotic behavior of the effective relaxation rates. It is strongly suggested that scattering from optical or zone-boundary phonons is important for magnon heat current relaxation in a high-temperature window of ΘD≲T<< J.

Self-interference between forward and backward propagating parts of a single acoustic plate mode

NASA Astrophysics Data System (ADS)

Germano, M.; Alippi, A.; Angelici, M.; Bettucci, A.

2002-04-01

Near and far fields of a particular (S1) Lamb mode, generated on a steel plate by means of a wedge transducer, are investigated. These show an oscillating behavior of the radial profile of the acoustic field amplitude that can be interpreted and modelled as interference phenomenon between forward and backward propagating parts of the Lamb mode, simultaneously generated at the interface between transducer and plate.

Self-interference between forward and backward propagating parts of a single acoustic plate mode.

PubMed

Germano, M; Alippi, A; Angelici, M; Bettucci, A

2002-04-01

Near and far fields of a particular (S(1)) Lamb mode, generated on a steel plate by means of a wedge transducer, are investigated. These show an oscillating behavior of the radial profile of the acoustic field amplitude that can be interpreted and modelled as interference phenomenon between forward and backward propagating parts of the Lamb mode, simultaneously generated at the interface between transducer and plate.

A conservative numerical scheme for modeling nonlinear acoustic propagation in thermoviscous homogeneous media

NASA Astrophysics Data System (ADS)

Diaz, Manuel A.; Solovchuk, Maxim A.; Sheu, Tony W. H.

2018-06-01

A nonlinear system of partial differential equations capable of describing the nonlinear propagation and attenuation of finite amplitude perturbations in thermoviscous media is presented. This system constitutes a full nonlinear wave model that has been formulated in the conservation form. Initially, this model is investigated analytically in the inviscid limit where it has been found that the resulting flux function fulfills the Lax-Wendroff theorem, and the scheme can match the solutions of the Westervelt and Burgers equations numerically. Here, high-order numerical descriptions of strongly nonlinear wave propagations become of great interest. For that matter we consider finite difference formulations of the weighted essentially non-oscillatory (WENO) schemes associated with explicit strong stability preserving Runge-Kutta (SSP-RK) time integration methods. Although this strategy is known to be computationally demanding, it is found to be effective when implemented to be solved in graphical processing units (GPUs). As we consider wave propagations in unbounded domains, perfectly matching layers (PML) have been also considered in this work. The proposed system model is validated and illustrated by using one- and two-dimensional benchmark test cases proposed in the literature for nonlinear acoustic propagation in homogeneous thermoviscous media.

Enhanced photoelastic modulation in silica phononic crystal cavities

NASA Astrophysics Data System (ADS)

Kim, Ingi; Iwamoto, Satoshi; Arakawa, Yasuhiko

2018-04-01

The enhanced photoelastic modulation in quasi-one-dimensional (1D) phononic crystal (PnC) cavities made of fused silica is experimentally demonstrated. A confined acoustic wave in the cavity can induce a large birefringence through the photoelastic effect and enable larger optical modulation amplitude at the same acoustic power. We observe a phase retardation of ∼26 mrad of light passing through the cavity when the exciting acoustic frequency is tuned to the cavity mode resonance of ∼500 kHz at 2.5 V. In the present experiment, a 16-fold enhancement of retardation in the PnC cavity is demonstrated compared with that in a bar-shaped silica structure. Spatially resolved optical retardation measurement reveals that the large retardation is realized only around the cavity reflecting the localized nature of the acoustic cavity mode. The enhanced interactions between acoustic waves and light can be utilized to improve the performance of acousto-optic devices such as photoelastic modulators.

Comment on "Anomalous wave propagation in a one-dimensional acoustic metamaterial having simultaneously negative mass density and Young's modulus" [J. Acoust. Soc. Am. 132, 2887-2895 (2012)].

PubMed

Marston, Philip L

2014-03-01

The phase and group velocities of elastic guided waves are important in the physical interpretation of high frequency scattering by fluid-loaded elastic shells. Outside the context of scattering, those properties are also important for understanding the energy flow in acoustic metamaterials. In a recent investigation of acoustic metamaterials exhibiting anomalous wave propagation [J. Acoust. Soc. Am. 132, 2887-2895 (2012)] criticism of negative group velocity terminology was generalized to elastic waves guided on ordinary materials. Some context and justification for retaining the identification of negative group velocities associated with a type of backscattering enhancement for shells are explained here. The phase evolution direction is determined by the boundary conditions.

Soft phonon modes driven huge difference on lattice thermal conductivity between topological semimetal WC and WN

NASA Astrophysics Data System (ADS)

Guo, San-Dong; Chen, Peng

2018-04-01

Topological semimetals are currently attracting increasing interest due to their potential applications in topological qubits and low-power electronics, which are closely related to their thermal transport properties. Recently, the triply degenerate nodal points near the Fermi level of WC are observed by using angle-resolved photoemission spectroscopy. In this work, by solving the Boltzmann transport equation based on first-principles calculations, we systematically investigate the phonon transport properties of topological semimetals WC and WN. The predicted room-temperature lattice thermal conductivities of WC (WN) along the a and c directions are 1140.64 (7.47) W m-1 K-1 and 1214.69 (5.39) W m-1 K-1. Considering the similar crystal structure of WC and WN, it is quite interesting to find that the thermal conductivity of WC is more than two orders of magnitude higher than that of WN. It is found that, different from WN, the large acoustic-optical (a-o) gap prohibits the acoustic+acoustic → optical (aao) scattering, which gives rise to very long phonon lifetimes, leading to ultrahigh lattice thermal conductivity in WC. For WN, the lack of an a-o gap is due to soft phonon modes in optical branches, which can provide more scattering channels for aao scattering, producing very short phonon lifetimes. Further deep insight can be attained from their different electronic structures. Distinctly different from that in WC, the density of states of WN at the Fermi level becomes very sharp, which leads to destabilization of WN, producing soft phonon modes. It is found that the small shear modulus G and C44 limit the stability of WN, compared with WC. Our studies provide valuable information for phonon transports in WC and WN, and motivate further experimental studies to study their lattice thermal conductivities.

Phonon thermodynamics of iron and cementite

NASA Astrophysics Data System (ADS)

Mauger, Lisa Mary

reversed after the magnetic transition and these same phonon modes lower their energies with temperature, consistent with observed thermal expansion. This atypical phonon behavior lowers the vibrational entropy of cementite up to the Curie temperature. The experimentally observed increase in low energy acoustic phonons affects the elastic behavior of Fe3C, increasing the isotropy of elastic response. First principles calculations link the observed phonon energy increases to specific vibrational modes that are polarized along the b-axis, which aligns with the closest Fe-Fe bonding direction. The nonharmonic behavior of the vibrational modes are discussed in the context of other observations of anomalous anisotropic magneto-volume behavior in Fe3C.

2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate

NASA Astrophysics Data System (ADS)

Tai, Po-Tse; Yu, Pyng; Tang, Jau

2010-08-01

In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes.

Effect of polarization field on mean free path of phonons in indium nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahoo, Sushant Kumar

2016-05-06

The effect of built-in-polarization field on mean free path of acoustic phonons in bulk wurtzite indium nitride (InN) has been theoretically investigated. The elastic constant of the material gets modified due to the existence of polarization field. As a result velocity and Debye frequency of phonons get enhanced. The various scattering rates of phonons are suppressed by the effect of polarization field, which implies an enhanced combined relaxation time. Thus phonons travel freely for a longer distance between two successive scatterings. This would enhance the thermal transport properties of the material when built-in-polarization field taken into account. Hence by themore » application of electric field the transport properties of such materials can be controlled as and when desired.« less

Enhancing phonon flow through one-dimensional interfaces by impedance matching

NASA Astrophysics Data System (ADS)

Polanco, Carlos A.; Ghosh, Avik W.

2014-08-01

We extend concepts from microwave engineering to thermal interfaces and explore the principles of impedance matching in 1D. The extension is based on the generalization of acoustic impedance to nonlinear dispersions using the contact broadening matrix Γ(ω), extracted from the phonon self energy. For a single junction, we find that for coherent and incoherent phonons, the optimal thermal conductance occurs when the matching Γ(ω) equals the Geometric Mean of the contact broadenings. This criterion favors the transmission of both low and high frequency phonons by requiring that (1) the low frequency acoustic impedance of the junction matches that of the two contacts by minimizing the sum of interfacial resistances and (2) the cut-off frequency is near the minimum of the two contacts, thereby reducing the spillage of the states into the tunneling regime. For an ultimately scaled single atom/spring junction, the matching criterion transforms to the arithmetic mean for mass and the harmonic mean for spring constant. The matching can be further improved using a composite graded junction with an exponential varying broadening that functions like a broadband antireflection coating. There is, however, a trade off as the increased length of the interface brings in additional intrinsic sources of scattering.

Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO 3

DOE PAGES

Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; ...

2015-02-10

In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO 3. The dispersions of the three acoustic phonon modes (LA along [100], TA 1 along [010], and TA 2 along [110]) and two low-energy optic phonon modes (LO and TO 1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature T N=640 K. In conclusion, this suggests that the magnetic order andmore » low-energy lattice dynamics in this multiferroic material are coupled.« less

Design of phononic band gaps in functionally graded piezocomposite materials by using topology optimization

NASA Astrophysics Data System (ADS)

Vatanabe, Sandro L.; Silva, Emílio C. N.

2011-04-01

One of the properties of composite materials is the possibility of having phononic band gaps, within which sound and vibrations at certain frequencies do not propagate. These materials are called Phononic Crystals (PCs). PCs with large band gaps are of great interest for many applications, such as transducers, elastic/ acoustic filters, noise control, and vibration shields. Most of previous works concentrates on PCs made of elastic isotropic materials; however, band gaps can be enlarged by using non-isotropic materials, such as piezoelectric materials. Since the main property of PCs is the presence of band gaps, one possible way to design structures which have a desired band gap is through Topology Optimization Method (TOM). TOM is a computational technique that determines the layout of a material such that a prescribed objective is maximized. Functionally Graded Materials (FGM) are composite materials whose properties vary gradually and continuously along a specific direction within the domain of the material. One of the advantages of applying the FGM concept to TOM is that it is not necessary a discrete 0-1 result, once the material gradation is part of the solution. Therefore, the interpretation step becomes easier and the dispersion diagram obtained from the optimization is not significantly modified. In this work, the main objective is to optimize the position and width of piezocomposite materials band gaps. Finite element analysis is implemented with Bloch-Floquet theory to solve the dynamic behavior of two-dimensional functionally graded unit cells. The results demonstrate that phononic band gaps can be designed by using this methodology.

Intrinsic phonon-limited charge carrier mobilities in thermoelectric SnSe

NASA Astrophysics Data System (ADS)

Ma, Jinlong; Chen, Yani; Li, Wu

2018-05-01

Within the past few years, tin selenide (SnSe) has attracted intense interest due to its remarkable thermoelectric potential for both n - and p -type crystals. In this work, the intrinsic phonon-limited electron/hole mobilities of SnSe are investigated using a Boltzmann transport equation based on first-principles calculated electron-phonon interactions. We find that the electrons have much larger mobilities than the holes. At room temperature, the mobilities of electrons along the a , b , and c axes are 325, 801, and 623 cm2/V s, respectively, whereas those of holes are 100, 299, and 291 cm2/V s, respectively. The anisotropy of mobilities is consistent with the reciprocal effective mass at band edges. The mode-specific analysis shows that the highest longitudinal optical phonons, rather than previously assumed acoustic phonons, dominate the scattering processes and consequently the mobilities in SnSe. The room-temperature largest mean free paths of electrons and holes in SnSe are about 21 and 13 nm, respectively.

Topological Acoustics

NASA Astrophysics Data System (ADS)

Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

2015-03-01

The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

Electrical detection and analysis of surface acoustic wave in line-defect two-dimensional piezoelectric phononic crystals

NASA Astrophysics Data System (ADS)

Cai, Feida; Li, Honglang; Tian, Yahui; Ke, Yabing; Cheng, Lina; Lou, Wei; He, Shitang

2018-03-01

Line-defect piezoelectric phononic crystals (PCs) show good potential applications in surface acoustic wave (SAW) MEMS devices for RF communication systems. To analyze the SAW characteristics in line-defect two-dimensional (2D) piezoelectric PCs, optical methods are commonly used. However, the optical instruments are complex and expensive, whereas conventional electrical methods can only measure SAW transmission of the whole device and lack spatial resolution. In this paper, we propose a new electrical experimental method with multiple receiving interdigital transducers (IDTs) to detect the SAW field distribution, in which an array of receiving IDTs of equal aperture was used to receive the SAW. For this new method, SAW delay lines with perfect and line-defect 2D Al/128°YXLiNbO3 piezoelectric PCs on the transmitting path were designed and fabricated. The experimental results showed that the SAW distributed mainly in the line-defect region, which agrees with the theoretical results.

High quality factor surface Fabry-Perot cavity of acoustic waves

NASA Astrophysics Data System (ADS)

Xu, Yuntao; Fu, Wei; Zou, Chang-ling; Shen, Zhen; Tang, Hong X.

2018-02-01

Surface acoustic wave (SAW) resonators are critical components in wireless communications and many sensing applications. They have also recently emerged as a subject of study in quantum acoustics at the single phonon level. Acoustic loss reduction and mode confinement are key performance factors in SAW resonators. Here, we report the design and experimental realization of high quality factor Fabry-Perot SAW resonators formed in between the tapered phononic crystal mirrors patterned on a GaN-on-sapphire material platform. The fabricated SAW resonators are characterized by both an electrical network analyzer and an optical heterodyne vibrometer. We observed standing Rayleigh waves inside the cavity, with an intrinsic quality factor exceeding 1.3 × 104 at ambient conditions.

Acoustic-optical phonon branch crossings and lattice thermal transport in La3Cu3X4 (X = P, As, Sb, and Bi) systems

NASA Astrophysics Data System (ADS)

Pandey, Tribhuwan; Polanco, Carlos A.; Lindsay, Lucas; Parker, David S.

Thermoelectric properties of La3Cu3X4 (X = P, As, Sb, and Bi) compounds are examined using first-principles density functional theory and Boltzmann transport calculations. It is well known that the lattice thermal conductivity (κl) of bulk materials typically decreases with increasing atomic masses of the constituent elements. In this study, however, we observe contrary behavior: lighter mass, larger sound velocity La3Cu3P4 and La3Cu3As4 systems have lower κl than heavier mass, smaller sound velocity La3Cu3Sb4 and La3Cu3Bi4 systems. Analysis of three phonon scattering rates and other phonon properties demonstrate that the trend in κl behavior is governed by Grüneisen parameters, a measure of phonon anharmonicity. The Grüneisen parameters and lower κl of the P and As compounds are closely related to an avoided crossing between the lowest optical branches and the longitudinal acoustic branch, which results in abrupt changes in Grüneisen parameters. Additionally, electronic structure calculations show heavy and light bands near the band edges, which lead to large power factors important for good thermoelectric performance. T. P, C. A. P, L. L. and D. S. P. acknowledge support from the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

Thermally triggered phononic gaps in liquids at THz scale

DOE PAGES

Bolmatov, Dima; Zhernenkov, Mikhail; Zavyalov, Dmitry; ...

2016-01-14

In this study we present inelastic X-ray scattering experiments in a diamond anvil cell and molecular dynamic simulations to investigate the behavior of phononic excitations in liquid Ar. The spectra calculated using molecular dynamics were found to be in a good agreement with the experimental data. Furthermore, we observe that, upon temperature increases, a low-frequency transverse phononic gap emerges while high-frequency propagating modes become evanescent at the THz scale. The effect of strong localization of a longitudinal phononic mode in the supercritical phase is observed for the first time. The evidence for the high-frequency transverse phononic gap due to themore » transition from an oscillatory to a ballistic dynamic regimes of motion is presented and supported by molecular dynamics simulations. This transition takes place across the Frenkel line thermodynamic limit which demarcates compressed liquid and non-compressed fluid domains on the phase diagram and is supported by calculations within the Green-Kubo phenomenological formalism. These results are crucial to advance the development of novel terahertz thermal devices, phononic lenses, mirrors, and other THz metamaterials.« less

Electronic and phononic modulation of MoS2 under biaxial strain

NASA Astrophysics Data System (ADS)

Moghadasi, A.; Roknabadi, M. R.; Ghorbani, S. R.; Modarresi, M.

2017-12-01

Dichalcogenides of transition metals are attractive material due to its unique properties. In this work, it has been investigated the electronic band structure, phonon spectrum and heat capacity of MoS2 under the applied tensile and compressive biaxial strain using the density functional theory. The Molybdenum disulfide under compressive (tensile) strain up to 6% (10%) has stable atomic structure without any negative frequency in the phonon dispersion curves. The tensile biaxial strain reduces the energy gap in the electronic band structure and the optical-acoustic gap in phonon dispersion curves. The tensile biaxial strain also increases the specific heat capacity. On the other hand, the compressive biaxial strain in this material increases phonon gap and reduces the heat capacity and the electronic band gap. The phonon softening/hardening is reported for tensile/compressive biaxial strain in MoS2. We report phonon hardening for out of plane ZA mode in the presence of both tensile and compressive strains. Results show that the linear variation of specific heat with strain (CV ∝ε) and square dependency of specific heat with the temperature (CV ∝T2) for low temperature regime. The results demonstrate that the applied biaxial strain tunes the electronic energy gap and modifies the phonon spectrum of MoS2.

Phonon group velocity and thermal conduction in superlattices

NASA Astrophysics Data System (ADS)

Tamura, Shin-Ichiro; Tanaka, Yukihiro; Maris, Humphrey J.

1999-07-01

With the use of a face-centered cubic model of lattice dynamics we calculate the group velocity of acoustic phonons in the growth direction of periodic superlattices. Comparing with the case of bulk solids, this component of the phonon group velocity is reduced due to the flattening of the dispersion curves associated with Brillouin-zone folding. The results are used to estimate semiquantitatively the effects on the lattice thermal conductivity in Si/Ge and GaAs/AlAs superlattices. For a Si/Ge superlattice an order of magnitude reduction is predicted in the ratio of superlattice thermal conductivity to phonon relaxation time [consistent with the results of P. Hyldgaard and G. D. Mahan, Phys. Rev. B 56, 10 754 (1997)]. For a GaAs/AlAs superlattice the corresponding reduction is rather small, i.e., a factor of 2-3. These effects are larger for the superlattices with larger unit period, contrary to the recent measurements of thermal conductivity in superlattices.

Rayleigh wave acoustic emission during crack propagation in steel

NASA Astrophysics Data System (ADS)

Horne, Michael R.

2003-07-01

An investigation was conducted of the existence of seismic surface pulses (SSP) on crack faces in near-failure fatigue. An SSP has components of various modes of wave propagation. The component with the largest amplitude is a Rayleigh surface wave pulse. The possibility that these surface modes have much higher amplitudes than bulk modes of acoustic emission (AE) was illustrated by an idealized thought experiment relating an SSP on a half-space to the response of crack faces to crack extension. A number of aspects of AE monitoring in finite objects were investigated. Attributes of surface wave propagation on the edge of a specimen were found to be easier to monitor than other modes of wave propagation. Wavelet analysis was used to compare the characteristics of brittle AE with other sources. A new testing paradigm was developed to reduce interference from secondary sources of AE and enhance the investigation of AE from critical crack behavior. Unique specimen design features were developed, data acquisition features sought and validated, a dead weight load frame was modified, and data analysis procedures were developed. Criteria based on velocity, frequency content, amplitude and shape were devised to determine if an AE event is an SSP. The tests were designed to mimic load conditions on structures such as bridges and hence investigate the difference between AE generated in field conditions and that of typical laboratory conditions. Varieties of steel, from very ductile to very brittle, were tested. It was concluded that plastic zone formation, considered a secondary source of AE, was found not to interfere with the SSP activity. The SSP was found experimentally to have 2-3 times the amplitude of the bulk wave AE. The lack of sufficient AE did not allow for determination of conclusive changes in the AE as the specimens approached failure. However, it was found that brittle crack extension in fatigue and ductile failure can produce wave propagation resembling the

Rayleigh wave acoustic emission during crack propagation in steel

NASA Astrophysics Data System (ADS)

Horne, Michael R.

An investigation was conducted of the existence of seismic surface pulses (SSP) on crack faces in near-failure fatigue. An SSP has components of various modes of wave propagation. The component with the largest amplitude is a Rayleigh surface wave pulse. The possibility that these surface modes have much higher amplitudes than bulk modes of acoustic emission (AE) was illustrated by an idealized thought experiment relating an SSP on a half-space to the response of crack faces to crack extension. A number of aspects of AE monitoring in finite objects were investigated. Attributes of surface wave propagation on the edge of a specimen were found to be easier to monitor than other modes of wave propagation. Wavelet analysis was used to compare the characteristics of brittle AE with other sources. A new testing paradigm was developed to reduce interference from secondary sources of AE and enhance the investigation of AE from critical crack behavior. Unique specimen design features were developed, data acquisition features sought and validated, a dead weight load frame was modified, and data analysis procedures were developed. Criteria based on velocity, frequency content, amplitude and shape were devised to determine if an AE event is an SSP. The tests were designed to mimic load conditions on structures such as bridges and hence investigate the difference between AE generated in field conditions and that of typical laboratory conditions. Varieties of steel, from very ductile to very brittle, were tested. It was concluded that plastic zone formation, considered a secondary source of AE, was found not to interfere with the SSP activity. The SSP was found experimentally to have 2-3 times the amplitude of the bulk wave AE. The lack of sufficient AE did not allow for determination of conclusive changes in the AE as the specimens approached failure. However, it was found that brittle crack extension in fatigue and ductile failure can produce wave propagation resembling the

Acoustic Phonons and Mechanical Properties of Ultra-Thin Porous Low-k Films: A Surface Brillouin Scattering Study

NASA Astrophysics Data System (ADS)

Zizka, J.; King, S.; Every, A.; Sooryakumar, R.

2018-04-01

To reduce the RC (resistance-capacitance) time delay of interconnects, a key development of the past 20 years has been the introduction of porous low-k dielectrics to replace the traditional use of SiO2. Moreover, in keeping pace with concomitant reduction in technology nodes, these low-k materials have reached thicknesses below 100 nm wherein the porosity becomes a significant fraction of the film volume. The large degree of porosity not only reduces mechanical strength of the dielectric layer but also renders a need for non-destructive approaches to measure the mechanical properties of such ultra-thin films within device configurations. In this study, surface Brillouin scattering (SBS) is utilized to determine the elastic constants, Poisson's ratio, and Young's modulus of these porous low-k SiOC:H films (˜ 25-250 nm thick) grown on Si substrates by probing surface acoustic phonons and their dispersions.

Acoustic Phonons and Mechanical Properties of Ultra-Thin Porous Low- k Films: A Surface Brillouin Scattering Study

NASA Astrophysics Data System (ADS)

Zizka, J.; King, S.; Every, A.; Sooryakumar, R.

2018-07-01

To reduce the RC (resistance-capacitance) time delay of interconnects, a key development of the past 20 years has been the introduction of porous low- k dielectrics to replace the traditional use of SiO2. Moreover, in keeping pace with concomitant reduction in technology nodes, these low- k materials have reached thicknesses below 100 nm wherein the porosity becomes a significant fraction of the film volume. The large degree of porosity not only reduces mechanical strength of the dielectric layer but also renders a need for non-destructive approaches to measure the mechanical properties of such ultra-thin films within device configurations. In this study, surface Brillouin scattering (SBS) is utilized to determine the elastic constants, Poisson's ratio, and Young's modulus of these porous low- k SiOC:H films (˜ 25-250 nm thick) grown on Si substrates by probing surface acoustic phonons and their dispersions.

Computational aero-acoustics for fan duct propagation and radiation. Current status and application to turbofan liner optimisation

NASA Astrophysics Data System (ADS)

Astley, R. J.; Sugimoto, R.; Mustafi, P.

2011-08-01

Novel techniques are presented to reduce noise from turbofan aircraft engines by optimising the acoustic treatment in engine ducts. The application of Computational Aero-Acoustics (CAA) to predict acoustic propagation and absorption in turbofan ducts is reviewed and a critical assessment of performance indicates that validated and accurate techniques are now available for realistic engine predictions. A procedure for integrating CAA methods with state of the art optimisation techniques is proposed in the remainder of the article. This is achieved by embedding advanced computational methods for noise prediction within automated and semi-automated optimisation schemes. Two different strategies are described and applied to realistic nacelle geometries and fan sources to demonstrate the feasibility of this approach for industry scale problems.

North Pacific Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea

DTIC Science & Technology

2016-06-21

the "Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical Society of America (Vol. 134, No . 4, Pt. 2 of 2 , October20 13...also listed. Fourteen (14) of these publications appeared in the " Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical

Phonon and magnon dispersions of incommensurate spin ladder compound Sr14Cu24O41

NASA Astrophysics Data System (ADS)

Chen, Xi; Bansal, Dipanshu; Sullivan, Sean; Zhou, Jianshi; Delaire, Olivier; Shi, Li

There are a variety of compounds consisting of two or more interpenetrating sublattices with lattice periods incommensurate at least along one crystal axis. One example is spin ladder compound Sr14Cu24O41 consisting of incommensurate spin ladder and spin chain sublattices. It has been predicted that unique phonon modes occur in these compounds due to the relative motion of the sublattices. In the low-wavelength limit, there is only one longitudinal acoustic mode due to the rigid translation of both sublattices. In addition, one extra pseudo-acoustic mode is present due to relative sliding motions of the two sublattices. Although the theoretical aspects of the lattice dynamics of incommensurate compounds have been studied, there have been few experimental investigations on their phonon dynamics. In this work, single crystals of Sr14Cu24O41are grown by the traveling solvent floating zone method. The phonon dispersion of Sr14Cu24O41 is studied through inelastic neutron scattering measurements in order to better understand its phonon dynamics. In addition, its magnon dispersion is investigated and correlated to the large directional magnon thermal conductivity. The measurements reveal a wealth of intriguing features on phonons and magnons in the spin ladder compound. This work is supported by ARO MURI program under Award # W911NF-14-1-0016.

Nonlocal electron-phonon coupling in the pentacene crystal: Beyond the Γ-point approximation

NASA Astrophysics Data System (ADS)

Yi, Yuanping; Coropceanu, Veaceslav; Brédas, Jean-Luc

2012-10-01

There is currently increasing interest in understanding the impact of the nonlocal (Peierls-type) electron-phonon mechanism on charge transport in organic molecular semiconductors. Most estimates of the non-local coupling constants reported in the literature are based on the Γ-point phonon modes. Here, the influence of phonon modes spanning the entire Brillouin zone (phonon dispersion) on the nonlocal electron-phonon couplings is investigated for the pentacene crystal. The phonon modes are obtained by using a supercell approach. The results underline that the overall nonlocal couplings are substantially underestimated by calculations taking sole account of the phonons at the Γ point of the unit cell. The variance of the transfer integrals based on Γ-point normal-mode calculations at room temperature is underestimated in some cases by 40% for herringbone-type dimers and by over 80% for cofacial dimers. Our calculations show that the overall coupling is somewhat larger for holes than for electrons. The results also suggest that the interactions of charge carriers (both electrons and holes) with acoustic and optical phonons are comparable. Therefore, an adequate description of the charge-transport properties in pentacene and similar systems requires that these two electron-phonon coupling mechanisms be treated on the same footing.

Experimental study of outdoor propagation of spherically speading periodic acoustic waves of finite amplitude

NASA Technical Reports Server (NTRS)

Theobald, M. A.

1977-01-01

The outdoor propagation of spherically spreading sound waves of finite amplitude was investigated. The main purpose of the experiments was to determine the extent to which the outdoor environment, mainly random inhomogeneity of the medium, affects finite amplitude propagation. Periodic sources with fundamental frequencies in the range 6 to 8 kHz and source levels SPLlm from 140 to 149 dB were used. The sources were an array of 7 to 10 horn drivers and a siren. The propagation path was vertical and parallel to an 85 m tower, whose elevator carried the traveling microphone. The general conclusions drawn from the experimental results were as follows. The inhomogeneities caused significant fluctuations in the instantaneous acoustic signal, but with sufficient time averaging of the measured harmonic levels, the results were comparable to results expected for propagation in a quiet medium. Propagation data for the fundamental of the siren approached within 1 dB of the weak shock saturation levels. Extra attenuation on the order of 8 dB was observed. The measurements generally confirmed the predictions of several theoretical models. The maximum propagation distance was 36 m. The narrowbeam arrays were much weaker sources. Nonlinear propagation distortion was produced, but the maximum value of extra attenuation measured was 1.5 dB. The maximum propagation distance was 76 m. The behavior of the asymetric waveforms received in one experiment qualitatively suggested that beam type diffraction effects were present. The role of diffraction of high intensity sound waves in radiation from a single horn was briefly investigated.

Phonons and superconductivity in fcc and dhcp lanthanum

NASA Astrophysics Data System (ADS)

Baǧcı, S.; Tütüncü, H. M.; Duman, S.; Srivastava, G. P.

2010-04-01

We have investigated the structural and electronic properties of lanthanum in the face-centered-cubic (fcc) and double hexagonal-close-packed (dhcp) phases using a generalized gradient approximation of the density functional theory and the ab initio pseudopotential method. It is found that double hexagonal-close-packed is the more stable phase for lanthanum. Differences in the density of states at the Fermi level between these two phases are pointed out and discussed in detail. Using the calculated lattice constant and electronic band structure for both phases, a linear response approach based on the density functional theory has been applied to study phonon modes, polarization characteristics of phonon modes, and electron-phonon interaction. Our phonon results show a softening behavior of the transverse acoustic branch along the Γ-L direction and the Γ-M direction for face-centered-cubic and double hexagonal-close-packed phases, respectively. Thus, the transverse-phonon linewidth shows a maximum at the zone boundary M(L) for the double hexagonal-close-packed phase (face-centered-cubic phase), where the transverse-phonon branch exhibits a dip. The electron-phonon coupling parameter λ is found to be 0.97 (1.06) for the double hexagonal-close-packed phase (face-centered-cubic phase), and the superconducting critical temperature is estimated to be 4.87 (dhcp) and 5.88 K (fcc), in good agreement with experimental values of around 5.0 (dhcp) and 6.0 K (fcc). A few superconducting parameters for the double hexagonal-close-packed phase have been calculated and compared with available theoretical and experimental results. Furthermore, the calculated superconducting parameters for both phases are compared between each other in detail.

Giant Phonon Anharmonicity and Anomalous Pressure Dependence of Lattice Thermal Conductivity in Y2Si2O7 silicate

PubMed Central

Luo, Yixiu; Wang, Jiemin; Li, Yiran; Wang, Jingyang

2016-01-01

Modification of lattice thermal conductivity (κL) of a solid by means of hydrostatic pressure (P) has been a crucially interesting approach that targets a broad range of advanced materials from thermoelectrics and thermal insulators to minerals in mantle. Although it is well documented knowledge that thermal conductivity of bulk materials normally increase upon hydrostatic pressure, such positive relationship is seriously challenged when it comes to ceramics with complex crystal structure and heterogeneous chemical bonds. In this paper, we predict an abnormally negative trend dκL/dP < 0 in Y2Si2O7 silicate using density functional theoretical calculations. The mechanism is disclosed as combined effects of slightly decreased group velocity and significantly augmented scattering of heat-carrying acoustic phonons in pressured lattice, which is originated from pressure-induced downward shift of low-lying optic and acoustic phonons. The structural origin of low-lying optic phonons as well as the induced phonon anharmonicity is also qualitatively elucidated with respect to intrinsic bonding heterogeneity of Y2Si2O7. The present results are expected to bring deeper insights for phonon engineering and modulation of thermal conductivity in complex solids with diverging structural flexibility, enormous bonding heterogeneity, and giant phonon anharmonicity. PMID:27430670

Experimental and theoretical studies of near-ground acoustic radiation propagation in the atmosphere

NASA Astrophysics Data System (ADS)

Belov, Vladimir V.; Burkatovskaya, Yuliya B.; Krasnenko, Nikolai P.; Rakov, Aleksandr S.; Rakov, Denis S.; Shamanaeva, Liudmila G.

2017-11-01

Results of experimental and theoretical studies of the process of near-ground propagation of monochromatic acoustic radiation on atmospheric paths from a source to a receiver taking into account the contribution of multiple scattering on fluctuations of atmospheric temperature and wind velocity, refraction of sound on the wind velocity and temperature gradients, and its reflection by the underlying surface for different models of the atmosphere depending the sound frequency, coefficient of reflection from the underlying surface, propagation distance, and source and receiver altitudes are presented. Calculations were performed by the Monte Carlo method using the local estimation algorithm by the computer program developed by the authors. Results of experimental investigations under controllable conditions are compared with theoretical estimates and results of analytical calculations for the Delany-Bazley impedance model. Satisfactory agreement of the data obtained confirms the correctness of the suggested computer program.

Phonon Speed, Not Scattering, Differentiates Thermal Transport in Lead Halide Perovskites.

PubMed

Elbaz, Giselle A; Ong, Wee-Liat; Doud, Evan A; Kim, Philip; Paley, Daniel W; Roy, Xavier; Malen, Jonathan A

2017-09-13

Thermal management plays a critical role in the design of solid state materials for energy conversion. Lead halide perovskites have emerged as promising candidates for photovoltaic, thermoelectric, and optoelectronic applications, but their thermal properties are still poorly understood. Here, we report on the thermal conductivity, elastic modulus, and sound speed of a series of lead halide perovskites MAPbX 3 (X = Cl, Br, I), CsPbBr 3 , and FAPbBr 3 (MA = methylammonium, FA = formamidinium). Using frequency domain thermoreflectance, we find that the room temperature thermal conductivities of single crystal lead halide perovskites range from 0.34 to 0.73 W/m·K and scale with sound speed. These results indicate that regardless of composition, thermal transport arises from acoustic phonons having similar mean free path distributions. A modified Callaway model with Born von Karmen-based acoustic phonon dispersion predicts that at least ∼70% of thermal conductivity results from phonons having mean free paths shorter than 100 nm, regardless of whether resonant scattering is invoked. Hence, nanostructures or crystal grains with dimensions smaller than 100 nm will appreciably reduce thermal transport. These results are important design considerations to optimize future lead halide perovskite-based photovoltaic, optoelectronic, and thermoelectric devices.

The Importance of Phonons with Negative Phase Quotient in Disordered Solids.

PubMed

Seyf, Hamid Reza; Lv, Wei; Rohskopf, Andrew; Henry, Asegun

2018-02-08

Current understanding of phonons is based on the phonon gas model (PGM), which is best rationalized for crystalline materials. However, most of the phonons/modes in disordered materials have a different character and thus may contribute to heat conduction in a fundamentally different way than is described by PGM. For the modes in crystals, which have sinusoidal character, one can separate the modes into two primary categories, namely acoustic and optical modes. However, for the modes in disordered materials, such designations may no longer rigorously apply. Nonetheless, the phase quotient (PQ) is a quantity that can be used to evaluate whether a mode more so shares a distinguishing property of acoustic vibrations manifested as a positive PQ, or a distinguishing property of an optical vibrations manifested as negative PQ. In thinking about this characteristic, there is essentially no intuition regarding the role of positive vs. negative PQ vibrational modes in disordered solids. Given this gap in understanding, herein we studied the respective contributions to thermal conductivity for several disordered solids as a function of PQ. The analysis sheds light on the importance of optical like/negative PQ modes in structurally/compositionally disordered solids, whereas in crystalline materials, the contributions of optical modes are usually small.

Electron-phonon interaction model and prediction of thermal energy transport in SOI transistor.

PubMed

Jin, Jae Sik; Lee, Joon Sik

2007-11-01

An electron-phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron-phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron-phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron-phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron-phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon-phonon scattering rates are lower than 4 x 10(10) S(-1).

Numerical Modeling of Footpoint-driven Magneto-acoustic Wave Propagation in a Localized Solar Flux Tube

NASA Astrophysics Data System (ADS)

Fedun, V.; Shelyag, S.; Erdélyi, R.

2011-01-01

In this paper, we present and discuss results of two-dimensional simulations of linear and nonlinear magneto-acoustic wave propagation through an open magnetic flux tube embedded in the solar atmosphere expanding from the photosphere through to the transition region and into the low corona. Our aim is to model and analyze the response of such a magnetic structure to vertical and horizontal periodic motions originating in the photosphere. To carry out the simulations, we employed our MHD code SAC (Sheffield Advanced Code). A combination of the VALIIIC and McWhirter solar atmospheres and coronal density profiles were used as the background equilibrium model in the simulations. Vertical and horizontal harmonic sources, located at the footpoint region of the open magnetic flux tube, are incorporated in the calculations, to excite oscillations in the domain of interest. To perform the analysis we have constructed a series of time-distance diagrams of the vertical and perpendicular components of the velocity with respect to the magnetic field lines at each height of the computational domain. These time-distance diagrams are subject to spatio-temporal Fourier transforms allowing us to build ω-k dispersion diagrams for all of the simulated regions in the solar atmosphere. This approach makes it possible to compute the phase speeds of waves propagating throughout the various regions of the solar atmosphere model. We demonstrate the transformation of linear slow and fast magneto-acoustic wave modes into nonlinear ones, i.e., shock waves, and also show that magneto-acoustic waves with a range of frequencies efficiently leak through the transition region into the solar corona. It is found that the waves interact with the transition region and excite horizontally propagating surface waves along the transition region for both types of drivers. Finally, we estimate the phase speed of the oscillations in the solar corona and compare it with the phase speed derived from

Electrons, phonons and superconductivity in rocksalt and tungsten-carbide phases of CrC.

PubMed

Tütüncü, H M; Baǧcı, S; Srivastava, G P; Akbulut, A

2012-11-14

We present results of ab initio theoretical investigations of the electronic structure, phonon dispersion relations, electron-phonon interaction and superconductivity in the rocksalt and tungsten-carbide phases of CrC. It is found that, compared to the stable tungsten-carbide phase, the metastable rocksalt phase is characterized by a much larger electronic density of states at the Fermi level. The phonon spectra of the rocksalt phase exhibit anomalies in the dispersion curves of both the transverse and longitudinal acoustic branches along the main symmetry directions. A combination of these characteristic electronic and phonon properties leads to an order of magnitude larger value of the electron-phonon coupling constant (λ = 2.66) for the rocksalt phase compared to that for the tungsten-carbide phase (λ = 0.24). Our calculations suggest that superconducting transition temperature values of 0.01 K and 25-35 K may be expected for the tungsten-carbide and rocksalt phases, respectively.

Flexocoupling impact on the generalized susceptibility and soft phonon modes in the ordered phase of ferroics

DOE PAGES

Morozovska, Anna N.; Vysochanskii, Yulian M.; Varenyk, Oleksandr V.; ...

2015-09-29

The impact of the flexoelectric effect on the generalized susceptibility and soft phonon dispersion is not well known in the long-range-ordered phases of ferroics. Within the Landau-Ginzburg-Devonshire approach we obtained analytical expressions for the generalized susceptibility and phonon dispersion relations in the ferroelectric phase. The joint action of the static and dynamic flexoelectric effects induces nondiagonal components of the generalized susceptibility, whose amplitude is proportional to the convolution of the spontaneous polarization with the flexocoupling constants. The flexocoupling essentially broadens the k spectrum of the generalized susceptibility and leads to an additional “pushing away” of the optical and acoustic softmore » mode phonon branches. The degeneracy of the transverse optical and acoustic modes disappears in the ferroelectric phase in comparison with the paraelectric phase due to the joint action of flexoelectric coupling and ferroelectric nonlinearity. Lastly, the results obtained might be mainly important for theoretical analyses of a broad spectrum of experimental data, including neutron and Brillouin scattering.« less

Effect of gas adsorption on acoustic wave propagation in MFI zeolite membrane materials: experiment and molecular simulation.

PubMed

Manga, Etoungh D; Blasco, Hugues; Da-Costa, Philippe; Drobek, Martin; Ayral, André; Le Clezio, Emmanuel; Despaux, Gilles; Coasne, Benoit; Julbe, Anne

2014-09-02

The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant.

Phonons on fcc (100), (110), and (111) surfaces using Lennard-Jones potentials. II. Temperature dependence of surface phonons studied with molecular dynamics

NASA Astrophysics Data System (ADS)

Koleske, D. D.; Sibener, S. J.

In this paper we present temperature dependent studies of the surface phonon dispersion relations for fcc (100), (110), and (111) faces using molecular dynamics (MD) simulations and Lennard-Jones potentials. This study was conducted in order to investigate how anharmonic potential terms influence the dynamical properties of the surface. This was accomplished by examining the temperature dependence of the Q-resolved phonon spectral density function. All phonon frequencies were found to decrease linearly in T as the temperature was increased, while at low temperatures the phonon linewidths increased linearly with T. At higher temperatures, some of the phonon linewidths changed from having a linear to a quadratic dependence on T. The temperature at which this T to T2 change occurs is surface dependent and occurs at the lowest temperature on the (110) surface. The T2 dependence arises from the increasing importance of higher-order phonon-phonon scattering terms. The phonons which exhibit T2 dependence tend to be modes which propagate perpendicularly or nearly perpendicularly to the direction of maximum root-mean-squared displacement (RMSD). This is especially true for the linewidth of the S 1 mode at overlineX on the (110) surface where, at T ≈ 15-23% of the melting temperature, the RMSD perpendicular to the atomic rows become larger than the RMSD normal to the surface. Our results indicate that the dynamics on the (110) surface may be significantly influenced by anharmonic potential terms at temperatures as low as 15% of the melting temperature.

Dispersion of folded phonons in {Si}/{Si xGe1- x} superlattices

NASA Astrophysics Data System (ADS)

Brugger, H.; Reiner, H.; Abstreiter, G.; Jorke, H.; Herzog, H. J.; Kasper, E.

Zone folding effects on acoustic phonons in {Si}/{Si xGe1- x} strained layer superlattices are studied by Raman spectroscopy. A quantitative explanation of the measured frequencies is given in terms of the elastic continuum theory. The scattering wavevector q s is varied by use of different laser lines to probe directly the phonon dispersion curve in the superlattices. For large period samples q s can be shifted through the new Brillouin zone boundary. We report on observation of a finite doublet splitting corresponding to the first zone-edge gap.

A realistic analysis of the phonon growth characteristics in a degenerate semiconductor using a simplified model of Fermi-Dirac distribution

NASA Astrophysics Data System (ADS)

Basu, A.; Das, B.; Middya, T. R.; Bhattacharya, D. P.

2017-01-01

The phonon growth characteristic in a degenerate semiconductor has been calculated under the condition of low temperature. If the lattice temperature is high, the energy of the intravalley acoustic phonon is negligibly small compared to the average thermal energy of the electrons. Hence one can traditionally assume the electron-phonon collisions to be elastic and approximate the Bose-Einstein (B.E.) distribution for the phonons by the simple equipartition law. However, in the present analysis at the low lattice temperatures, the interaction of the non equilibrium electrons with the acoustic phonons becomes inelastic and the simple equipartition law for the phonon distribution is not valid. Hence the analysis is made taking into account the inelastic collisions and the complete form of the B.E. distribution. The high-field distribution function of the carriers given by Fermi-Dirac (F.D.) function at the field dependent carrier temperature, has been approximated by a well tested model that apparently overcomes the intrinsic problem of correct evaluation of the integrals involving the product and powers of the Fermi function. Hence the results thus obtained are more reliable compared to the rough estimation that one may obtain from using the exact F.D. function, but taking recourse to some over simplified approximations.

Unusual phonon behavior and ultra-low thermal conductance of monolayer InSe.

PubMed

Zhou, Hangbo; Cai, Yongqing; Zhang, Gang; Zhang, Yong-Wei

2017-12-21

Monolayer indium selenide (InSe) possesses numerous fascinating properties, such as high electron mobility, quantum Hall effect and anomalous optical response. However, its phonon properties, thermal transport properties and the origin of its structural stability remain unexplored. Using first-principles calculations, we show that the atoms in InSe are highly polarized and such polarization causes strong long-range dipole-dipole interaction (DDI). For acoustic modes, DDI is essential for maintaining its structural stability. For optical modes, DDI causes a significant frequency shift of its out-of-phase vibrations. Surprisingly, we observed that there were two isolated frequency regimes, which were completely separated from other frequency regimes with large frequency gaps. Within each frequency regime, only a single phonon mode exists. We further reveal that InSe possesses the lowest thermal conductance among the known two-dimensional materials due to the low cut-off frequency, low phonon group velocities and the presence of large frequency gaps. These unique behaviors of monolayer InSe can enable the fabrication of novel devices, such as thermoelectric module, single-mode phonon channel and phononic laser.

Propagation of acoustic waves in a one-dimensional macroscopically inhomogeneous poroelastic material.

PubMed

Gautier, G; Kelders, L; Groby, J P; Dazel, O; De Ryck, L; Leclaire, P

2011-09-01

Wave propagation in macroscopically inhomogeneous porous materials has received much attention in recent years. The wave equation, derived from the alternative formulation of Biot's theory of 1962, was reduced and solved recently in the case of rigid frame inhomogeneous porous materials. This paper focuses on the solution of the full wave equation in which the acoustic and the elastic properties of the poroelastic material vary in one-dimension. The reflection coefficient of a one-dimensional macroscopically inhomogeneous porous material on a rigid backing is obtained numerically using the state vector (or the so-called Stroh) formalism and Peano series. This coefficient can then be used to straightforwardly calculate the scattered field. To validate the method of resolution, results obtained by the present method are compared to those calculated by the classical transfer matrix method at both normal and oblique incidence and to experimental measurements at normal incidence for a known two-layers porous material, considered as a single inhomogeneous layer. Finally, discussion about the absorption coefficient for various inhomogeneity profiles gives further perspectives. © 2011 Acoustical Society of America

A spectral hybridizable discontinuous Galerkin method for elastic-acoustic wave propagation

NASA Astrophysics Data System (ADS)

Terrana, S.; Vilotte, J. P.; Guillot, L.

2018-04-01

, when element polynomials of order k are used, and to exhibit the classical spectral convergence of SEM. Additional inexpensive local post-processing in both the elastic and the acoustic case allow to achieve higher convergence orders. The HDG scheme provides a natural framework for coupling classical, continuous Galerkin SEM with HDG-SEM in the same simulation, and it is shown numerically in this paper. As such, the proposed HDG-SEM can combine the efficiency of the continuous SEM with the flexibility of the HDG approaches. Finally, more complex numerical results, inspired from real geophysical applications, are presented to illustrate the capabilities of the method for wave propagation in heterogeneous elastic-acoustic media with complex geometries.

Acoustic signal propagation and measurement in natural stream channels for application to surrogate bed load measurements: Halfmoon Creek, Colorado

USDA-ARS?s Scientific Manuscript database

Monitoring sediment-generated noise using submerged hydrophones is a surrogate method for measuring bed load transport in streams with the potential for improving estimates of bed load transport through widespread, inexpensive monitoring. Understanding acoustic signal propagation in natural stream e...

Experimental verification of acoustic pseudospin multipoles in a symmetry-broken snowflakelike topological insulator

NASA Astrophysics Data System (ADS)

Zhang, Zhiwang; Tian, Ye; Cheng, Ying; Liu, Xiaojun; Christensen, Johan

2017-12-01

Topologically protected wave engineering in artificially structured media resides at the frontier of ongoing metamaterials research, which is inspired by quantum mechanics. Acoustic analogs of electronic topological insulators have recently led to a wealth of new opportunities in manipulating sound propagation by means of robust edge mode excitations through analogies drawn to exotic quantum states. A variety of artificial acoustic systems hosting topological edge states have been proposed analogous to the quantum Hall effect, topological insulators, and Floquet topological insulators in electronic systems. However, those systems were characterized by a fixed geometry and a very narrow frequency response, which severely hinders the exploration and design of useful applications. Here we establish acoustic multipolar pseudospin states as an engineering degree of freedom in time-reversal invariant flow-free phononic crystals and develop reconfigurable topological insulators through rotation of their meta-atoms and reshaping of the metamolecules. Specifically, we show how rotation forms man-made snowflakelike molecules, whose topological phase mimics pseudospin-down (pseudospin-up) dipolar and quadrupolar states, which are responsible for a plethora of robust edge confined properties and topological controlled refraction disobeying Snell's law.

ZnO films on /001/-cut (110)-propagating GaAs substrates for surface acoustic wave device applications

NASA Technical Reports Server (NTRS)

Hickernell, Frederick S.; Higgins, Robert J.; Jen, Cheng-Kuei; Kim, Yoonkee; Hunt, William D.

1995-01-01

A potential application for piezoelectric films substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on /001/-cut group of (110) zone axes-propagating GaAs substrates are investigated in this article, including SAW velocity, effective piezoelectric coupling constant, propagation loss, diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films of different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(sup 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2 or Si3N4 on /001/-cut GaAs samples are reported using two different techniques: (1) knife-edge laser probe, (2) line-focus-beam scanning acoustic microscope. It was found that near the group of (110) zone axes propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the (100) direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

ZnO Films on {001}-Cut <110>-Propagating GaAs Substrates for Surface Acoustic Wave Device Applications

NASA Technical Reports Server (NTRS)

Kim, Yoonkee; Hunt, William D.; Hickernell, Frederick S.; Higgins, Robert J.; Jen, Cheng-Kuei

1995-01-01

A potential application for piezoelectric films on GaAs substrates is the monolithic integration of surface acoustic wave (SAW) devices with GaAs electronics. Knowledge of the SAW properties of the layered structure is critical for the optimum and accurate design of such devices. The acoustic properties of ZnO films sputtered on {001}-cut <110> -propagating GaAs substrates are investigated in this article, including SAW Velocity effective piezoelectric coupling constant, propagation loss. diffraction, velocity surface, and reflectivity of shorted and open metallic gratings. The measurements of these essential SAW properties for the frequency range between 180 and 360 MHz have been performed using a knife-edge laser probe for film thicknesses over the range of 1.6-4 micron and with films or different grain sizes. The high quality of dc triode sputtered films was observed as evidenced by high K(exp 2) and low attenuation. The measurements of the velocity surface, which directly affects the SAW diffraction, on the bare and metalized ZnO on SiO2, or Si3N4 on {001}-cut GaAs samples are reported using two different techniques: 1) knife-edge laser probe, 2) line-focus-beam scanning acoustic microscope. It was found that near the <110> propagation direction, the focusing SAW property of the bare GaAs changes into a nonfocusing one for the layered structure, but a reversed phenomenon exists near the <100> direction. Furthermore, to some extent the diffraction of the substrate can be controlled with the film thickness. The reflectivity of shorted and open gratings are also analyzed and measured. Zero reflectivity is observed for a shorted grating. There is good agreement between the measured data and theoretical values.

Free-field propagation of high intensity noise

NASA Technical Reports Server (NTRS)

Welz, Joseph P.; Mcdaniel, Oliver H.

1990-01-01

Observed spectral data from supersonic jet aircraft are known to contain much more high frequency energy than can be explained by linear acoustic propagation theory. It is believed that the high frequency energy is an effect of nonlinear distortion due to the extremely high acoustic levels generated by the jet engines. The objective, to measure acoustic waveform distortion for spherically diverging high intensity noise, was reached by using an electropneumatic acoustic source capable of generating sound pressure levels in the range of 140 to 160 decibels (re 20 micro Pa). The noise spectrum was shaped to represent the spectra generated by jet engines. Two microphones were used to capture the acoustic pressure waveform at different points along the propagation path in order to provide a direct measure of the waveform distortion as well as spectral distortion. A secondary objective was to determine that the observed distortion is an acoustic effect. To do this an existing computer prediction code that deals with nonlinear acoustic propagation was used on data representative of the measured data. The results clearly demonstrate that high intensity jet noise does shift the energy in the spectrum to the higher frequencies along the propagation path. In addition, the data from the computer model are in good agreement with the measurements, thus demonstrating that the waveform distortion can be accounted for with nonlinear acoustic theory.

Preserving the Helmholtz dispersion relation: One-way acoustic wave propagation using matrix square roots

NASA Astrophysics Data System (ADS)

Keefe, Laurence

2016-11-01

Parabolized acoustic propagation in transversely inhomogeneous media is described by the operator update equation U (x , y , z + Δz) =eik0 (- 1 +√{ 1 + Z }) U (x , y , z) for evolution of the envelope of a wavetrain solution to the original Helmholtz equation. Here the operator, Z =∇T2 + (n2 - 1) , involves the transverse Laplacian and the refractive index distribution. Standard expansion techniques (on the assumption Z << 1)) produce pdes that approximate, to greater or lesser extent, the full dispersion relation of the original Helmholtz equation, except that none of them describe evanescent/damped waves without special modifications to the expansion coefficients. Alternatively, a discretization of both the envelope and the operator converts the operator update equation into a matrix multiply, and existing theorems on matrix functions demonstrate that the complete (discrete) Helmholtz dispersion relation, including evanescent/damped waves, is preserved by this discretization. Propagation-constant/damping-rates contour comparisons for the operator equation and various approximations demonstrate this point, and how poorly the lowest-order, textbook, parabolized equation describes propagation in lined ducts.

Phonon group velocity and thermal conduction in superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamura, S.; Tanaka, Y.; Maris, H.J.

1999-07-01

With the use of a face-centered cubic model of lattice dynamics we calculate the group velocity of acoustic phonons in the growth direction of periodic superlattices. Comparing with the case of bulk solids, this component of the phonon group velocity is reduced due to the flattening of the dispersion curves associated with Brillouin-zone folding. The results are used to estimate semiquantitatively the effects on the lattice thermal conductivity in Si/Ge and GaAs/AlAs superlattices. For a Si/Ge superlattice an order of magnitude reduction is predicted in the ratio of superlattice thermal conductivity to phonon relaxation time [consistent with the results ofmore » P. Hyldgaard and G. D. Mahan, Phys. Rev. B {bold 56}, 10&hthinsp;754 (1997)]. For a GaAs/AlAs superlattice the corresponding reduction is rather small, i.e., a factor of 2{endash}3. These effects are larger for the superlattices with larger unit period, contrary to the recent measurements of thermal conductivity in superlattices. {copyright} {ital 1999} {ital The American Physical Society}« less

Optimal design of tunable phononic bandgap plates under equibiaxial stretch

NASA Astrophysics Data System (ADS)

Hedayatrasa, Saeid; Abhary, Kazem; Uddin, M. S.; Guest, James K.

2016-05-01

Design and application of phononic crystal (PhCr) acoustic metamaterials has been a topic with tremendous growth of interest in the last decade due to their promising capabilities to manipulate acoustic and elastodynamic waves. Phononic controllability of waves through a particular PhCr is limited only to the spectrums located within its fixed bandgap frequency. Hence the ability to tune a PhCr is desired to add functionality over its variable bandgap frequency or for switchability. Deformation induced bandgap tunability of elastomeric PhCr solids and plates with prescribed topology have been studied by other researchers. Principally the internal stress state and distorted geometry of a deformed phononic crystal plate (PhP) changes its effective stiffness and leads to deformation induced tunability of resultant modal band structure. Thus the microstructural topology of a PhP can be altered so that specific tunability features are met through prescribed deformation. In the present study novel tunable PhPs of this kind with optimized bandgap efficiency-tunability of guided waves are computationally explored and evaluated. Low loss transmission of guided waves throughout thin walled structures makes them ideal for fabrication of low loss ultrasound devices and structural health monitoring purposes. Various tunability targets are defined to enhance or degrade complete bandgaps of plate waves through macroscopic tensile deformation. Elastomeric hyperelastic material is considered which enables recoverable micromechanical deformation under tuning finite stretch. Phononic tunability through stable deformation of phononic lattice is specifically required and so any topology showing buckling instability under assumed deformation is disregarded. Nondominated sorting genetic algorithm (GA) NSGA-II is adopted for evolutionary multiobjective topology optimization of hypothesized tunable PhP with square symmetric unit-cell and relevant topologies are analyzed through finite

Quantum Regime of a Two-Dimensional Phonon Cavity

NASA Astrophysics Data System (ADS)

Bolgar, Aleksey N.; Zotova, Julia I.; Kirichenko, Daniil D.; Besedin, Ilia S.; Semenov, Aleksander V.; Shaikhaidarov, Rais S.; Astafiev, Oleg V.

2018-06-01

We realize the quantum regime of a surface acoustic wave (SAW) resonator by demonstrating vacuum Rabi mode splitting due to interaction with a superconducting artificial atom. Reaching the quantum regime is physically difficult and technologically challenging since SAW devices consist of large arrays of narrow metal strips. This work paves the way for realizing analogues of quantum optical phenomena with phonons and can be useful in on-chip quantum electronics.

Propagation and scattering of acoustic-vorticity waves in annular swirling flows

NASA Astrophysics Data System (ADS)

Golubev, Vladimir Viktorovich

1997-08-01

The dissertation presents a fundamental extension of unsteady aerodynamic theory developed to predict fluctuating forces on aircraft structural components. These excitations may result from a variety of upstream flow non-uniformities such as atmospheric turbulence, airframe tip vortices and wakes, engine inlet distortions and secondary flows. In the frame of reference of a downstream aircraft component, an upstream flow non- uniformity appears as a propagating vorticity wave (a gust). Classical treatment of gust interaction problems developed for uniform, potential upstream mean flows is based on the fact that it is possible to consider separately incident or scattered acoustic, entropic and vortical modes of unsteady flow motion. A purely vortical gust remains 'frozen' as it convects with the flow. The coupling between different unsteady components may occur only at the surface of a solid structure, or in the close vicinity of a lifting body. The classical approach, however, is not justified for an aircraft engine system where the internal turbomachinery flow is non-uniform and non-potential as it exhibits a strong swirling motion. In such a flow, acting centrifugal and Coriolis forces couple the various unsteady modes which thus can no longer be determined independently of each other. The new developed theory follows the decomposition of unsteady velocity field into vortical and potential components. In spite of the modal coupling, this decomposition elucidates the physical phenomena associated with unsteady swirling motion by indicating the degree of interaction between the various modes. It paves the way for generalizing the classical definition of a gust for vortical swirling flows. The concept of a generalized gust is developed based on the eigenmode pseudospectral analysis of the coupled equations of unsteady swirling motion. This analysis reveals two distinct regions of eigenvalues corresponding to pressure-dominated nearly-sonic and vorticity- dominated

Intrinsic to extrinsic phonon lifetime transition in a GaAs-AlAs superlattice.

PubMed

Hofmann, F; Garg, J; Maznev, A A; Jandl, A; Bulsara, M; Fitzgerald, E A; Chen, G; Nelson, K A

2013-07-24

We have measured the lifetimes of two zone-center longitudinal acoustic phonon modes, at 320 and 640 GHz, in a 14 nm GaAs/2 nm AlAs superlattice structure. By comparing measurements at 296 and 79 K we separate the intrinsic contribution to phonon lifetime determined by phonon-phonon scattering from the extrinsic contribution due to defects and interface roughness. At 296 K, the 320 GHz phonon lifetime has approximately equal contributions from intrinsic and extrinsic scattering, whilst at 640 GHz it is dominated by extrinsic effects. These measurements are compared with intrinsic and extrinsic scattering rates in the superlattice obtained from first-principles lattice dynamics calculations. The calculated room-temperature intrinsic lifetime of longitudinal phonons at 320 GHz is in agreement with the experimentally measured value of 0.9 ns. The model correctly predicts the transition from predominantly intrinsic to predominantly extrinsic scattering; however the predicted transition occurs at higher frequencies. Our analysis indicates that the 'interfacial atomic disorder' model is not entirely adequate and that the observed frequency dependence of the extrinsic scattering rate is likely to be determined by a finite correlation length of interface roughness.

Effect of Phonon Drag on the Thermopower in a Parabolic Quantum Well

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasanov, Kh. A., E-mail: xanlarhasanli@rambler.ru; Huseynov, J. I.; Dadashova, V. V.

2016-03-15

The theory of phonon-drag thermopower resulting from a temperature gradient in the plane of a two-dimensional electron gas layer in a parabolic quantum well is developed. The interaction mechanisms between electrons and acoustic phonons are considered, taking into account potential screening of the interaction. It is found that the effect of electron drag by phonons makes a significant contribution to the thermopower of the two-dimensional electron gas. It is shown that the consideration of screening has a significant effect on the drag thermopower. For the temperature dependence of the thermopower in a parabolic GaAs/AlGaAs quantum well in the temperature rangemore » of 1–10 K, good agreement between the obtained theoretical results and experiments is shown.« less

Ab initio phonon point defect scattering and thermal transport in graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polanco, Carlos A.; Lindsay, Lucas R.

Here, we study the scattering of phonons from point defects and their effect on lattice thermal conductivity κ using a parameter-free ab initio Green's function methodology. Specifically, we focus on the scattering of phonons by boron (B), nitrogen (N), and phosphorus substitutions as well as single- and double-carbon vacancies in graphene. We show that changes of the atomic structure and harmonic interatomic force constants locally near defects govern the strength and frequency trends of the scattering of out-of-plane acoustic (ZA) phonons, the dominant heat carriers in graphene. ZA scattering rates due to N substitutions are nearly an order of magnitudemore » smaller than those for B defects despite having similar mass perturbations. Furthermore, ZA phonon scattering rates from N defects decrease with increasing frequency in the lower-frequency spectrum in stark contrast to expected trends from simple models. ZA phonon-vacancy scattering rates are found to have a significantly softer frequency dependence (~ω 0) in graphene than typically employed in phenomenological models. The rigorous Green's function calculations demonstrate that typical mass-defect models do not adequately describe ZA phonon-defect scattering rates. Our ab initio calculations capture well the trend of κ vs vacancy density from experiments, though not the magnitudes. In conclusion, this work elucidates important insights into phonon-defect scattering and thermal transport in graphene, and demonstrates the applicability of first-principles methods toward describing these properties in imperfect materials.« less

Ab initio phonon point defect scattering and thermal transport in graphene

DOE PAGES

Polanco, Carlos A.; Lindsay, Lucas R.

2018-01-04

Here, we study the scattering of phonons from point defects and their effect on lattice thermal conductivity κ using a parameter-free ab initio Green's function methodology. Specifically, we focus on the scattering of phonons by boron (B), nitrogen (N), and phosphorus substitutions as well as single- and double-carbon vacancies in graphene. We show that changes of the atomic structure and harmonic interatomic force constants locally near defects govern the strength and frequency trends of the scattering of out-of-plane acoustic (ZA) phonons, the dominant heat carriers in graphene. ZA scattering rates due to N substitutions are nearly an order of magnitudemore » smaller than those for B defects despite having similar mass perturbations. Furthermore, ZA phonon scattering rates from N defects decrease with increasing frequency in the lower-frequency spectrum in stark contrast to expected trends from simple models. ZA phonon-vacancy scattering rates are found to have a significantly softer frequency dependence (~ω 0) in graphene than typically employed in phenomenological models. The rigorous Green's function calculations demonstrate that typical mass-defect models do not adequately describe ZA phonon-defect scattering rates. Our ab initio calculations capture well the trend of κ vs vacancy density from experiments, though not the magnitudes. In conclusion, this work elucidates important insights into phonon-defect scattering and thermal transport in graphene, and demonstrates the applicability of first-principles methods toward describing these properties in imperfect materials.« less

Ab initio phonon point defect scattering and thermal transport in graphene

NASA Astrophysics Data System (ADS)

Polanco, Carlos A.; Lindsay, Lucas

2018-01-01

We study the scattering of phonons from point defects and their effect on lattice thermal conductivity κ using a parameter-free ab initio Green's function methodology. Specifically, we focus on the scattering of phonons by boron (B), nitrogen (N), and phosphorus substitutions as well as single- and double-carbon vacancies in graphene. We show that changes of the atomic structure and harmonic interatomic force constants locally near defects govern the strength and frequency trends of the scattering of out-of-plane acoustic (ZA) phonons, the dominant heat carriers in graphene. ZA scattering rates due to N substitutions are nearly an order of magnitude smaller than those for B defects despite having similar mass perturbations. Furthermore, ZA phonon scattering rates from N defects decrease with increasing frequency in the lower-frequency spectrum in stark contrast to expected trends from simple models. ZA phonon-vacancy scattering rates are found to have a significantly softer frequency dependence (˜ω0 ) in graphene than typically employed in phenomenological models. The rigorous Green's function calculations demonstrate that typical mass-defect models do not adequately describe ZA phonon-defect scattering rates. Our ab initio calculations capture well the trend of κ vs vacancy density from experiments, though not the magnitudes. This work elucidates important insights into phonon-defect scattering and thermal transport in graphene, and demonstrates the applicability of first-principles methods toward describing these properties in imperfect materials.

Boron arsenide phonon dispersion from inelastic x-ray scattering: Potential for ultrahigh thermal conductivity

NASA Astrophysics Data System (ADS)

Ma, Hao; Li, Chen; Tang, Shixiong; Yan, Jiaqiang; Alatas, Ahmet; Lindsay, Lucas; Sales, Brian C.; Tian, Zhiting

2016-12-01

Cubic boron arsenide (BAs) was predicted to have an exceptionally high thermal conductivity (k ) ˜2000 W m-1K-1 at room temperature, comparable to that of diamond, based on first-principles calculations. Subsequent experimental measurements, however, only obtained a k of ˜200 W m-1K-1 . To gain insight into this discrepancy, we measured phonon dispersion of single-crystal BAs along high symmetry directions using inelastic x-ray scattering and compared these with first-principles calculations. Based on the measured phonon dispersion, we have validated the theoretical prediction of a large frequency gap between acoustic and optical modes and bunching of acoustic branches, which were considered the main reasons for the predicted ultrahigh k . This supports its potential to be a super thermal conductor if very-high-quality single-crystal samples can be synthesized.

Boron arsenide phonon dispersion from inelastic x-ray scattering: Potential for ultrahigh thermal conductivity

DOE PAGES

Ma, Hao; Li, Chen; Tang, Shixiong; ...

2016-12-14

Cubic boron arsenide (BAs) was predicted to have an exceptionally high thermal conductivity (k) ~2000 Wm -1K -1 at room temperature, comparable to that of diamond, based on first-principles calculations. Subsequent experimental measurements, however, only obtained a k of ~200 Wm-1K-1. To gain insight into this discrepancy, we measured phonon dispersion of single crystal BAs along high symmetry directions using inelastic x-ray scattering (IXS) and compared these with first-principles calculations. Based on the measured phonon dispersion, we have validated the theoretical prediction of a large frequency gap between acoustic and optical modes and bunching of acoustic branches, which were consideredmore » the main reasons for the predicted ultrahigh k. This supports its potential to be a super thermal conductor if very high-quality single crystal samples can be synthesized.« less

Phonon conductivity metrics for compact, linked-cage, layered, and filled-cage crystals, using ab initio, molecular dynamics and Boltzmann transport treatments

NASA Astrophysics Data System (ADS)

Huang, Baoling

Atomic-level thermal transport in compact, layered, linked-cage, and filled-cage crystals is investigated using a multiscale approach, combines the ab initio calculation, molecular dynamics (MD), Boltzman transport equations (BTE), and the kinetic theory. These materials are of great interests in energy storage, transport, and conversion. The structural metrics of phonon conductivity of these crystals are then explored. An atomic structure-based model is developed for the understanding the relationship between the atomic structure and phonon transport in compact crystals at high temperatures. The elemental electronegativity, element mass, and the arrangement of bonds are found to be the dominant factors to determine the phonon conductivity. As an example of linked-cage crystals, the phonon conductivity of MOF-5 is investigated over a wide temperature range using MD simulations and the Green-Kubo method. The temperature dependence of the thermal conductivity of MOF-5 is found to be weak at high temperatures, which results from the suppression of the long-range acoustic phonon transport by the special linked-cage structure. The mean free path of the majority of phonons in MOF-5 is limited by the cage size. The phonon and electron transport in layered Bi2Te3 structure are investigated using the first-principle calculations, MD, and BTE. Strong anisotropy has been found for both phonon and electron transport due to the special layered structure. The long-range acoustic phonons dominate the phonon transport with a strong temperature and direction dependence. Temperature dependence of the energy gap and appropriate modelling of relaxation times are found to be important for the prediction of the electrical transport in the intrinsic regime. The scattering by the acoustic, optical, and polar-optical phonons are found to dominate the electron transport. For filled skutterudite structure, strong coupling between the filler and the host is found, which contradicts the

Bottom Interaction in Ocean Acoustic Propagation

DTIC Science & Technology

2013-09-30

critical depth). What is the relationship between the seismic (ground motion) noise on the seafloor and the acoustic noise in the water column? What...detections and observations on non-traditional sensors such as deep boreholes in the seafloor in water depths well- below the critical depth. Third...press). "Estimating the horizontal 4 and vertical direction-of-arrival of water-borne seismic signals in the northern Philippine Sea," J. Acoust

Hydrodynamic phonon drift and second sound in a (20,20) single-wall carbon nanotube

NASA Astrophysics Data System (ADS)

Lee, Sangyeop; Lindsay, Lucas

2017-05-01

Two hydrodynamic features of phonon transport, phonon drift and second sound, in a (20,20) single-wall carbon nanotube (SWCNT) are discussed using lattice dynamics calculations employing an optimized Tersoff potential for atomic interactions. We formally derive a formula for the contribution of drift motion of phonons to total heat flux at steady state. It is found that the drift motion of phonons carries more than 70 % and 90 % of heat at 300 and 100 K, respectively, indicating that phonon flow can be reasonably approximated as hydrodynamic if the SWCNT is long enough to avoid ballistic phonon transport. The dispersion relation of second sound is derived from the Peierls-Boltzmann transport equation with Callaway's scattering model and quantifies the speed of second sound and its relaxation. The speed of second sound is around 4000 m/s in a (20,20) SWCNT and the second sound can propagate more than 10 µm in an isotopically pure (20,20) SWCNT for frequency around 1 GHz at 100 K.

Flexural phonon limited phonon drag thermopower in bilayer graphene

NASA Astrophysics Data System (ADS)

Ansari, Mohd Meenhaz; Ashraf, SSZ

2018-05-01

We investigate the phonon drag thermopower from flexural phonons as a function of electron temperature and carrier concentration in the Bloch-Gruneisen regime in non-strained bilayer graphene using Boltzmann transport equation approach. The flexural phonons are expected to be the major source of intrinsic scattering mechanism in unstrained bilayer graphene due to their large density. The flexural phonon modes dispersion relation is quadratic so these low energy flexural phonons abound at room temperature and as a result deform the bilayer graphene sheet in the out of plane direction and affects the transport properties. We also produce analytical result for phonon-drag thermopower from flexural phonons and find that phonon-drag thermopower depicts T2 dependence on temperature and n-1 on carrier concentration.

Surface acoustic waves in acoustic superlattice lithium niobate coated with a waveguide layer

NASA Astrophysics Data System (ADS)

Yang, G. Y.; Du, J. K.; Huang, B.; Jin, Y. A.; Xu, M. H.

2017-04-01

The effects of the waveguide layer on the band structure of Rayleigh waves are studied in this work based on a one-dimensional acoustic superlattice lithium niobate substrate coated with a waveguide layer. The present phononic structure is formed by the periodic domain-inverted single crystal that is the Z-cut lithium niobate substrate with a waveguide layer on the upper surface. The plane wave expansion method (PWE) is adopted to determine the band gap behavior of the phononic structure and validated by the finite element method (FEM). The FEM is also used to investigate the transmission of Rayleigh waves in the phononic structure with the interdigital transducers by means of the commercial package COMSOL. The results show that, although there is a homogeneous waveguide layer on the surface, the band gap of Rayleigh waves still exist. It is also found that increasing the thickness of the waveguide layer, the band width narrows and the band structure shifts to lower frequency. The present approach can be taken as an efficient tool in designing of phononic structures with waveguide layer.

Quantum interference between two phonon paths and reduced heat transport in diamond lattice with atomic-scale planar defects

NASA Astrophysics Data System (ADS)

Kosevich, Yu. A.; Strelnikov, I. A.

2018-02-01

Destructive quantum interference between the waves propagating through laterally inhomogeneous layer can result in their total reflection, which in turn reduces energy flux carried by these waves. We consider the systems of Ge atoms, which fully or partly, in the chequer-wise order, fill a crystal plane in diamond-like Si lattice. We have revealed that a single type of the atomic defects, which are placed in identical positions in different unit cells in the defect crystal plane, can result in double transmission antiresonances of phonon wave packets. This new effect we relate with the complex structure of the diamond-like unit cell, which comprises two atoms in different positions and results in two distinct vibration resonances in two interfering phonon paths. We also consider the propagation of phonon wave packets in the superlatticies made of the defect planes, half-filled in the chequer-wise order with Ge atoms. We have revealed relatively broad phonon stop bands with center frequencies at the transmission antiresonances. We elaborate the equivalent analytical quasi-1D lattice model of the two phonon paths through the complex planar defect in the diamond-like lattice and describe the reduction of phonon heat transfer through the atomic-scale planar defects.

Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Song, Jin Dong; Srinivasan, Kartik

2016-01-01

Optomechanical cavities have been studied for applications ranging from sensing to quantum information science. Here, we develop a platform for nanoscale cavity optomechanical circuits in which optomechanical cavities supporting co-localized 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency (RF) field through the piezo-electric effect, which produces acoustic waves that are routed and coupled to the optomechanical cavity by phononic crystal waveguides, or optically through the strong photoelastic effect. Along with mechanical state preparation and sensitive readout, we use this to demonstrate an acoustic wave interference effect, similar to atomic coherent population trapping, in which RF-driven coherent mechanical motion is cancelled by optically-driven motion. Manipulating cavity optomechanical systems with equal facility through both photonic and phononic channels enables new architectures for signal transduction between the optical, electrical, and mechanical domains. PMID:27446234

Magnon-phonon interconversion in a dynamically reconfigurable magnetic material

NASA Astrophysics Data System (ADS)

Guerreiro, Sergio C.; Rezende, Sergio M.

2015-12-01

The ferrimagnetic insulator yttrium iron garnet (YIG) is an important material in the field of magnon spintronics, mainly because of its low magnetic losses. YIG also has very low acoustic losses, and for this reason the conversion of a state of magnetic excitation (magnons) into a state of lattice vibration (phonons), or vice versa, broadens its possible applications in spintronics. Since the magnetic parameters can be varied by some external action, the magnon-phonon interconversion can be tuned to perform a desired function. We present a quantum theory of the interaction between magnons and phonons in a ferromagnetic material subject to a dynamic variation of the applied magnetic field. It is shown that when the field gradient at the magnetoelastic crossover region is much smaller than a critical value, an initial elastic excitation can be completely converted into a magnetic excitation, or vice versa. This occurs with conservation of linear momentum and spin angular momentum, implying that phonons created by the conversion of magnons have spin angular momentum and carry spin current. It is shown further that if the system is initially in a quantum coherent state, its coherence properties are maintained regardless of the time dependence of the field.

Studies of Water V. Five Phonons in Protonic Semiconductor Lattice Model of Pure Liquid Water

NASA Astrophysics Data System (ADS)

Jie, Binbin; Sah, Chihtang

2017-07-01

We report physics based confirmation (~1% RMS deviation), by existing experimental data, of proton-prohol (proton-hole) ion product (pH) and mobilities in pure liquid water (0-100{}{{o}}C, 1-atm pressure) anticipated from our melted-ice Hexagonal-Close-Packed (H{}2O){}4 Lattice Model. Five phonons are identified. (1) A propagating protonic phonon (520.9 meV from lone-pair-blue-shifted stretching mode of isolated water molecule) absorbed to generate a proton-prohol pair or detrap a tightly-bound proton. (2) Two (173.4 and 196.6 meV) bending-breathing protonic-proholic or protonic phonons absorbed during de-trapping-limited proton or proton-prohol mobilities. (3) Two propagating oxygenic-wateric Debye-Dispersive phonons (30.3 and 27.5 meV) absorbed during scattering-limited proton or proton-prohol mobilities. Summer School in Theoretical Physics funded by the National Natural Science Foundation of China, on Soft Materials Physics, hosted by the Physics Department of Xiamen University, China, during August 1 to 14, 2016. This was also just presented at the 2017 March Meeting (March 14 to 16) of the American Physical Society in New Orleans, USA.

Phonon Transport at the Interfaces of Vertically Stacked Graphene and Hexagonal Boron Nitride Heterostructures

DOE PAGES

Yan, Zhequan; Chen, Liang; Yoon, Mina; ...

2016-01-12

Hexagonal boron nitride (h-BN) is a substrate for graphene based nano-electronic devices. We investigate the ballistic phonon transport at the interface of vertically stacked graphene and h-BN heterostructures using first principles density functional theory and atomistic Green's function simulations considering the influence of lattice stacking. We compute the frequency and wave-vector dependent transmission function and observe distinct stacking-dependent phonon transmission features for the h-BN/graphene/h-BN sandwiched systems. We find that the in-plane acoustic modes have the dominant contributions to the phonon transmission and thermal boundary conductance (TBC) for the interfaces with the carbon atom located directly on top of the boronmore » atom (C–B matched) because of low interfacial spacing. The low interfacial spacing is a consequence of the differences in the effective atomic volume of N and B and the difference in the local electron density around N and B. For the structures with the carbon atom directly on top of the nitrogen atom (C–N matched), the spatial distance increases and the contribution of in-plane modes to the TBC decreases leading to higher contributions by out-of-plane acoustic modes. We find that the C–B matched interfaces have stronger phonon–phonon coupling than the C–N matched interfaces, which results in significantly higher TBC (more than 50%) in the C–B matched interface. The findings in this study will provide insights to understand the mechanism of phonon transport at h-BN/graphene/h-BN interfaces, to better explain the experimental observations and to engineer these interfaces to enhance heat dissipation in graphene based electronic devices.« less

Probe And Enhancement Of SBS Based Phonons In Infrared Fibers Using Waveguide Coupled External Radiation

NASA Astrophysics Data System (ADS)

Yu, Chung; Chong, Yat C.; Fong, Chee K.

1989-06-01

Interaction of GHz and MHz radiation with CO2 laser propagation in a silver halide fiber using sBs based phonon coupling is furthet investigated. The external signal serves to both probe and enhance laser generated sBs phonons in the fiber. Efficient coupling of microwave radiation into the fiber is accomplished by placing the fiber in a hollow metallic waveguide, designed and constructed to transmit the dominant mode in the 0.9-2.0 GHz band. MHz radiation is conveniently coupled into the fiber using the guided microwave radiation as carrier. Phonon emissions from the fiber under CO2 laser pumping are first established on a spectrum analyzer; low frequency generators ale then tuned to match these frequencies and their maximum interaction recorded. Such interactions are systematically studied by monitoring the amplitude and waveform of the reflected and transmitted laser pulse at various power levels and frequencies of the externally coupled radiation. A plot of reflected laser power versus incident laser power reveals a distinct sBs generated phonon threshold. Variouslaunch directions of the GHz and MHz radiation with respect to the direction of laser propagation are realized to verify theory governing sBs interactions. The MHz radiation and its associated phonons in the fiber are convenient tools for probing sBs related phenomenon in infrared fibers.

25th Anniversary Article: Ordered Polymer Structures for the Engineering of Photons and Phonons

PubMed Central

Lee, Jae-Hwang; Koh, Cheong Yang; Singer, Jonathan P; Jeon, Seog-Jin; Maldovan, Martin; Stein, Ori; Thomas, Edwin L

2014-01-01

The engineering of optical and acoustic material functionalities via construction of ordered local and global architectures on various length scales commensurate with and well below the characteristic length scales of photons and phonons in the material is an indispensable and powerful means to develop novel materials. In the current mature status of photonics, polymers hold a pivotal role in various application areas such as light-emission, sensing, energy, and displays, with exclusive advantages despite their relatively low dielectric constants. Moreover, in the nascent field of phononics, polymers are expected to be a superior material platform due to the ability for readily fabricated complex polymer structures possessing a wide range of mechanical behaviors, complete phononic bandgaps, and resonant architectures. In this review, polymer-centric photonic and phononic crystals and metamaterials are highlighted, and basic concepts, fabrication techniques, selected functional polymers, applications, and emerging ideas are introduced. PMID:24338738

Coupling Nuclear Induced Phonon Propagation with Conversion Electron Moessbauer Spectroscopy

DTIC Science & Technology

2015-06-18

penetrating and a small detector with low density will be insensitive to the gammas. Thus, a small gas proportional counter is ideal for this application ...and Materials Science Vol. 1. Plenum: New York, 1993. 16. Long, G. J. and Stevens, J. G., eds. (1986) " Industrial applications of the Mössbauer...proportional gas detector attached to left side of 1” diameter stainless steel type-310 bar, phonon source encased in a mounting device attached to the right

Scattering of Acoustic Waves from Ocean Boundaries

DTIC Science & Technology

2015-09-30

of buried mines and improve SONAR performance in shallow water. OBJECTIVES 1) Determination of the correct physical model of acoustic propagation... acoustic parameters in the ocean. APPROACH 1) Finite Element Modeling for Range Dependent Waveguides: Finite element modeling is applied to a...roughness measurements for reverberation modeling . GLISTEN data provide insight into the role of biology on acoustic propagation and scattering

Experimental investigation of starting characteristics and wave propagation from a shallow open cavity and its acoustic emission at supersonic speed

NASA Astrophysics Data System (ADS)

Pandian, S.; Desikan, S. L. N.; Niranjan, Sahoo

2018-01-01

Experiments were carried out on a shallow open cavity (L/D = 5) at a supersonic Mach number (M = 1.8) to understand its transient starting characteristics, wave propagation (inside and outside the cavity) during one vortex shedding cycle, and acoustic emission. Starting characteristics and wave propagation were visualized through time resolved schlieren images, while acoustic emissions were captured through unsteady pressure measurements. Results showed a complex shock system during the starting process which includes characteristics of the bifurcated shock system, shock train, flow separation, and shock wave boundary layer interaction. In one vortex shedding cycle, vortex convection from cavity leading edge to cavity trailing edge was observed. Flow features outside the cavity demonstrated the formation and downstream movement of a λ-shock due to the interaction of shock from the cavity leading edge and shock due to vortex and generation of waves on account of shear layer impingement at the cavity trailing edge. On the other hand, interesting wave structures and its propagation were monitored inside the cavity. In one vortex shedding cycle, two waves such as a reflected compression wave from a cavity leading edge in the previous vortex shedding cycle and a compression wave due to the reflection of Mach wave at the cavity trailing edge corner in the current vortex shedding cycle were visualized. The acoustic emission from the cavity indicated that the 2nd to 4th modes/tones are dominant, whereas the 1st mode contains broadband spectrum. In the present studies, the cavity feedback mechanism was demonstrated through a derived parameter coherence coefficient.

Pressure effect on phonon frequencies in some transition metals: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Kazanc, S.; Ozgen, S.

2005-08-01

It is important to determine the atomic lattice vibrations of metallic materials, under high-pressure conditions, due to its effects on material properties such as thermal, electrical and optical conductions. In this work, we have investigated the changes of acoustic phonon frequencies with hydrostatic pressure for Cu, Ni, Al, Ag and Au transition metals, using molecular dynamics (MD) simulations based on embedded atom method (EAM). For this aim, we have adopted the embedded atom potential proposed by Sutton and Chen. The phonon frequencies have been calculated from the dynamical matrix for [1 0 0], [1 1 0] and [1 1 1] high symmetry directions of the Brillouin zone. The obtained results show that the hydrostatic pressure causes an increment in phonon frequencies, and this rising do not depend linearly on the increasing pressure.

Isotope scattering and phonon thermal conductivity in light atom compounds: LiH and LiF

DOE PAGES

Lindsay, Lucas R.

2016-11-08

Engineered isotope variation is a pathway toward modulating lattice thermal conductivity (κ) of a material through changes in phonon-isotope scattering. The effects of isotope variation on intrinsic thermal resistance is little explored, as varying isotopes have relatively small differences in mass and thus do not affect bulk phonon dispersions. However, for light elements isotope mass variation can be relatively large (e.g., hydrogen and deuterium). Using a first principles Peierls-Boltzmann transport equation approach the effects of isotope variance on lattice thermal transport in ultra-low-mass compound materials LiH and LiF are characterized. The isotope mass variance modifies the intrinsic thermal resistance viamore » modulation of acoustic and optic phonon frequencies, while phonon-isotope scattering from mass disorder plays only a minor role. This leads to some unusual cases where values of isotopically pure systems ( 6LiH, 7Li 2H and 6LiF) are lower than the values from their counterparts with naturally occurring isotopes and phonon-isotope scattering. However, these differences are relatively small. The effects of temperature-driven lattice expansion on phonon dispersions and calculated κ are also discussed. This work provides insight into lattice thermal conductivity modulation with mass variation and the interplay of intrinsic phonon-phonon and phonon-isotope scattering in interesting light atom systems.« less

Microfabricated bulk wave acoustic bandgap device

DOEpatents

Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, Carol

2010-06-08

A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

Microfabricated bulk wave acoustic bandgap device

DOEpatents

Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, legal representative, Carol

2010-11-23

A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

Influence of phonon reservoir on photon blockade in a driven quantum dot-cavity system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Bo; Li, Gao-xiang, E-mail: gaox@phy.ccnu.edu.cn; Zhu, Jia-pei, E-mail: fengxue0506@163.com

2016-03-14

We theoretically investigate the influence of the phonon bath on photon blockade in a simultaneously driven dot-cavity system. An optimal condition for avoiding two-photon excitation of a cavity field is put forward which can be achieved by modulating the phase difference and the strengths of the driving fields. The second-order correlation function and the mean photon number of the cavity field are discussed. In the absence of phonon effect, the strong photon blockade in a moderate quantum dot (QD)-cavity coupling regime occurs, which can be attributed to the destructive quantum interference arisen from different transition paths induced by simultaneously drivingmore » the dressed QD-cavity system. The participation of acoustic-phonon reservoir produces new transition channels for the QD-cavity system, which leads to the damage of destructive interference. As a result, the photon blockade effect is hindered when taking the electron-phonon interaction into account. It is also found that the temperature of the phonon reservoir is disadvantageous for the generation of photon blockade.« less

Effects of atmospheric variations on acoustic system performance

NASA Technical Reports Server (NTRS)

Nation, Robert; Lang, Stephen; Olsen, Robert; Chintawongvanich, Prasan

1993-01-01

Acoustic propagation over medium to long ranges in the atmosphere is subject to many complex, interacting effects. Of particular interest at this point is modeling low frequency (less than 500 Hz) propagation for the purpose of predicting ranges and bearing accuracies at which acoustic sources can be detected. A simple means of estimating how much of the received signal power propagated directly from the source to the receiver and how much was received by turbulent scattering was developed. The correlations between the propagation mechanism and detection thresholds, beamformer bearing estimation accuracies, and beamformer processing gain of passive acoustic signal detection systems were explored.

Airy acoustical-sheet spinner tweezers

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2016-09-01

The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in

Polar Fluctuations in Metal Halide Perovskites Uncovered by Acoustic Phonon Anomalies

DOE PAGES

Guo, Peijun; Xia, Yi; Gong, Jue; ...

2017-09-28

Solution-processable metal-halide perovskites (MHPs) offer great promise for efficient light harvesting and emitting devices due to their long carrier lifetime and superior carrier transport characteristics. Ferroelectric effects, a hallmark of traditional oxide perovskites, was proposed to be a mechanism to suppress carrier recombination and enhance charge transport in MHPs, but the existence and influence of such polar order is still of considerable debate. Here we performed transient reflection measurements on single crystals of both inorganic and organic-inorganic (hybrid) MHPs over a range of temperatures, and demonstrate significant phonon softening in the cubic phases close to the cubic-to-tetragonal phase transition temperatures.more » Such phonon softening indicates the formation of polar domains, which grow in size upon cooling and can persist in the low-temperature tetragonal and orthorhombic phases. Our results link the extraordinary electronic properties of MHPs to the spontaneous polarizations which can contribute to more efficient charge separation and characteristics of an indirect bandgap.« less

Nonlinear control of high-frequency phonons in spider silk

NASA Astrophysics Data System (ADS)

Schneider, Dirk; Gomopoulos, Nikolaos; Koh, Cheong Y.; Papadopoulos, Periklis; Kremer, Friedrich; Thomas, Edwin L.; Fytas, George

2016-10-01

Spider dragline silk possesses superior mechanical properties compared with synthetic polymers with similar chemical structure due to its hierarchical structure comprised of partially crystalline oriented nanofibrils. To date, silk’s dynamic mechanical properties have been largely unexplored. Here we report an indirect hypersonic phononic bandgap and an anomalous dispersion of the acoustic-like branch from inelastic (Brillouin) light scattering experiments under varying applied elastic strains. We show the mechanical nonlinearity of the silk structure generates a unique region of negative group velocity, that together with the global (mechanical) anisotropy provides novel symmetry conditions for gap formation. The phononic bandgap and dispersion show strong nonlinear strain-dependent behaviour. Exploiting material nonlinearity along with tailored structural anisotropy could be a new design paradigm to access new types of dynamic behaviour.

Revealing the mechanism of passive transport in lipid bilayers via phonon-mediated nanometre-scale density fluctuations

DOE PAGES

Zhernenkov, Mikhail; Bolmatov, Dima; Soloviov, Dmitry; ...

2016-05-12

We report the high resolution inelastic x-ray study of the in-plane phonon excitations in dipalmitoyl phosphatidylcholine (DPPC) above and below main transition temperature. In the L β' gel phase, we observe high frequency longitudinal phonon mode previously predicted by the molecular dynamics simulations and for the first time, we reveal low frequency weakly dispersive transverse acoustic mode which softens and exhibits a low-frequency phonon gap when the DPPC lipid transitions into the L α fluid phase. The phonon softening of the high frequency longitudinal excitations and the transformation of the transverse excitations upon the phase transition from the L β'more » to L α phase is explained within the framework of the phonon theory of liquids. These findings illustrate the importance of the collective dynamics of biomembranes and reveal that hydrocarbon tails can act as an efficient mediator in controlling the passive transport across the bilayer plane.« less

Acoustic Tomography of the Atmospheric Surface Layer

DTIC Science & Technology

2014-11-28

Report Title Acoustic tomography of the atmospheric surface layer (ASL) is based on the measurements of the travel times of sound propagation between...SECURITY CLASSIFICATION OF: Acoustic tomography of the atmospheric surface layer (ASL) is based on the measurements of the travel times of sound ...organ. In the case of acoustic tomography of the atmospheric surface layer (ASL), the travel times of sound propagation between speakers and

Coupling between plate vibration and acoustic radiation

NASA Technical Reports Server (NTRS)

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1992-01-01

A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far-field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far-field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

Origin of the "waterfall" effect in phonon dispersion of relaxor perovskites.

PubMed

Hlinka, J; Kamba, S; Petzelt, J; Kulda, J; Randall, C A; Zhang, S J

2003-09-05

We have undertaken an inelastic neutron scattering study of the perovskite relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O3 with 8% PbTiO3 (PZN-8%PT) in order to elucidate the origin of the previously reported unusual kink on the low frequency transverse phonon dispersion curve (known as the "waterfall effect"). We show that its position (q(wf)) depends on the choice of the Brillouin zone and that the relation of q(wf) to the size of the polar nanoregions is highly improbable. The waterfall phenomenon is explained in the framework of a simple model of coupled damped harmonic oscillators representing the acoustic and optic phonon branches.

Phonon-assisted indirect transitions in angle-resolved photoemission spectra of graphite and graphene

NASA Astrophysics Data System (ADS)

Ayria, Pourya; Tanaka, Shin-ichiro; Nugraha, Ahmad R. T.; Dresselhaus, Mildred S.; Saito, Riichiro

2016-08-01

Indirect transitions of electrons in graphene and graphite are investigated by means of angle-resolved photoemission spectroscopy (ARPES) with several different incident photon energies and light polarizations. The theoretical calculations of the indirect transition for graphene and for a single crystal of graphite are compared with the experimental measurements for highly-oriented pyrolytic graphite and a single crystal of graphite. The dispersion relations for the transverse optical (TO) and the out-of-plane longitudinal acoustic (ZA) phonon modes of graphite and the TO phonon mode of graphene can be extracted from the inelastic ARPES intensity. We find that the TO phonon mode for k points along the Γ -K and K -M -K' directions in the Brillouin zone can be observed in the ARPES spectra of graphite and graphene by using a photon energy ≈11.1 eV. The relevant mechanism in the ARPES process for this case is the resonant indirect transition. On the other hand, the ZA phonon mode of graphite can be observed by using a photon energy ≈6.3 eV through a nonresonant indirect transition, while the ZA phonon mode of graphene within the same mechanism should not be observed.

Acoustic manipulation of oscillating spherical bodies: Emergence of axial negative acoustic radiation force

NASA Astrophysics Data System (ADS)

Rajabi, Majid; Mojahed, Alireza

2016-11-01

In this paper, emergence of negative axial acoustic radiation force on a rigid oscillating spherical body is investigated for acoustic manipulation purposes. The problem of plane acoustic wave scattering from an oscillating spherical body submerged in an ideal acoustic fluid medium is solved. For the case of oscillating direction collinear with the wave propagation wave number vector (desired path), it has been shown that the acoustic radiation force, as a result of nonlinear acoustic wave interaction with bodies can be expressed as a linear function of incident wave field and the oscillation properties of the oscillator (i.e., amplitude and phase of oscillation). The negative (i.e., pulling effects) and positive (i.e., pushing effects) radiation force situations are divided in oscillation complex plane with a specific frequency-dependant straight line. This characteristic line defines the radiation force cancellation state. In order to investigate the stability of the mentioned manipulation strategy, the case of misaligned oscillation of sphere with the wave propagation direction is studied. The proposed methodology may suggest a novel concept of single-beam acoustic handling techniques based on smart carriers.

In-plane time-harmonic elastic wave motion and resonance phenomena in a layered phononic crystal with periodic cracks.

PubMed

Golub, Mikhail V; Zhang, Chuanzeng

2015-01-01

This paper presents an elastodynamic analysis of two-dimensional time-harmonic elastic wave propagation in periodically multilayered elastic composites, which are also frequently referred to as one-dimensional phononic crystals, with a periodic array of strip-like interior or interface cracks. The transfer matrix method and the boundary integral equation method in conjunction with the Bloch-Floquet theorem are applied to compute the elastic wave fields in the layered periodic composites. The effects of the crack size, spacing, and location, as well as the incidence angle and the type of incident elastic waves on the wave propagation characteristics in the composite structure are investigated in details. In particular, the band-gaps, the localization and the resonances of elastic waves are revealed by numerical examples. In order to understand better the wave propagation phenomena in layered phononic crystals with distributed cracks, the energy flow vector of Umov and the corresponding energy streamlines are visualized and analyzed. The numerical results demonstrate that large energy vortices obstruct elastic wave propagation in layered phononic crystals at resonance frequencies. They occur before the cracks reflecting most of the energy transmitted by the incoming wave and disappear when the problem parameters are shifted from the resonant ones.

Interactive Sound Propagation using Precomputation and Statistical Approximations