Non-relativistic solar electrons
NASA Technical Reports Server (NTRS)
Lin, R. P.
1974-01-01
Summary of both the direct spacecraft observations of nonrelativistic solar electrons, and observations of the X-ray and radio emission generated by these particles at the sun and in the interplanetary medium. These observations bear on three physical processes basic to energetic particle phenomena: (1) the acceleration of particles in tenuous plasmas; (2) the propagation of energetic charged particles in a disordered magnetic field, and (3) the interaction of energetic charged particles with tenuous plasmas to produce electromagnetic radiation. Because these electrons are frequently accelerated and emitted by the sun, mostly in small and relatively simple flares, it is possible to define a detailed physical picture of these processes. In many small solar flares nonrelativistic electrons accelerated during flash phase constitute the bulk of the total flare energy. Thus the basic flare mechanism in these flares essentially converts the available flare energy into fast electrons. Nonrelativistic electrons exhibit a wide variety of propagation modes in the interplanetary medium, ranging from diffusive to essentially scatter-free. This variability in the propagation may be explained in terms of the distribution of interplanetary magnetic field fluctuations.
Electron-Electron Interaction in the Non-Relativistic Limit
NASA Astrophysics Data System (ADS)
Malik, F. Bary
The electron-electron potential in the one-photon exchange approximation with the omission of the spin-spin interaction, leads to the classical Coulomb interaction, but the inclusion of the latter results in the Møller interaction. Bethe and Fermi showed that the latter interaction leads to the Breit potential, if a few of the terms in the expansion of the retardation effect are considered. In this article, it is shown that the higher order terms omitted in the Bethe-Fermi treatment reduces to terms of the same order in Dirac's alpha-matrices considered by Bethe and Fermi. This raises questions whether the Breit interaction is the appropriate first order correction to the Coulomb potential in the non-relativistic limit. It is pointed out that the nature of the interaction between two bound (1s) electron derived by Brown using the Schwinger formalism of the quantum electrodynamics but proposed empirically in 1929 by Gaunt could be a better correction to the Coulomb potential for bound electrons in atoms. The calculated energies using these matrix elements plus the vacuum polarization energies are in reasonable agreement with the data. For comparison, calculated energies using the Breit interaction plus vacuum polarization energies are also presented.
Electron-Electron Interaction in the Non-Relativistic Limit
NASA Astrophysics Data System (ADS)
Malik, F. Bary
2011-03-01
The electron-electron potential in the one-photon exchange approximation with the omission of the spin-spin interaction, leads to the classical Coulomb interaction, but the inclusion of the latter results in the Møller interaction. Bethe and Fermi showed that the latter interaction leads to the Breit potential, if a few of the terms in the expansion of the retardation effect are considered. In this article, it is shown that the higher order terms omitted in the Bethe-Fermi treatment reduces to terms of the same order in Dirac's alpha-matrices considered by Bethe and Fermi. This raises questions whether the Breit interaction is the appropriate first order correction to the Coulomb potential in the non-relativistic limit. It is pointed out that the nature of the interaction between two bound (1s) electron derived by Brown using the Schwinger formalism of the quantum electrodynamics but proposed empirically in 1929 by Gaunt could be a better correction to the Coulomb potential for bound electrons in atoms. The calculated energies using these matrix elements plus the vacuum polarization energies are in reasonable agreement with the data. For comparison, calculated energies using the Breit interaction plus vacuum polarization energies are also presented.
Hussain, S.; Mahmood, S.; Rehman, Aman-ur-
2014-11-15
Linear and nonlinear propagation of magnetosonic waves in the perpendicular direction to the ambient magnetic field is studied in dense plasmas for non-relativistic and ultra-relativistic degenerate electrons pressure. The sources of nonlinearities are the divergence of the ions and electrons fluxes, Lorentz forces on ions and electrons fluids and the plasma current density in the system. The Korteweg-de Vries equation for magnetosonic waves propagating in the perpendicular direction of the magnetic field is derived by employing reductive perturbation method for non-relativistic as well as ultra-relativistic degenerate electrons pressure cases in dense plasmas. The plots of the magnetosonic wave solitons are also shown using numerical values of the plasma parameters such a plasma density and magnetic field intensity of the white dwarfs from literature. The dependence of plasma density and magnetic field intensity on the magnetosonic wave propagation is also pointed out in dense plasmas for both non-relativistic and ultra-relativistic degenerate electrons pressure cases.
Sahu, Biswajit; Sinha, Anjana; Roychoudhury, Rajkumar
2015-09-15
A numerical study is presented of the nonlinear dynamics of a magnetized, cold, non-relativistic plasma, in the presence of electron-ion collisions. The ions are considered to be immobile while the electrons move with non-relativistic velocities. The primary interest is to study the effects of the collision parameter, external magnetic field strength, and the initial electromagnetic polarization on the evolution of the plasma system.
Tuning ground states and excitations in complex electronic materials
Bishop, A.R.
1996-09-01
Modern electronic materials are characterized by a great variety of broken-symmetry ground states and excitations. Their control requires understanding and tuning underlying driving forces of spin-charge-lattice coupling, critical to macroscopic properties and applications. We report representative model calculations which demonstrate some of the richness of the phenomena and the challenges for successful microscopic modeling.
On the correct electronic ground state of Tc( g )
Rard, J.A. ); Rand, M.H. ); Thornback, J.R. ); Wanner, H. )
1991-05-01
The electronic ground state of Tc({ital g}) is {sup 6}{ital S}{sub 5/2}, which arises from a 4{ital d}{sup 5}5{ital s}{sup 2} valence electron configuration. However, there are several treatises and review articles in which the ground state is incorrectly given as {ital S}{sub 9/2} with a valence electron configuration of 4{ital d}{sup 6}5{ital s}{sup 1}. The origin of this incorrect assignment was traced to the misinterpretation of a paper on the hyperfine splitting of the optical spectrum of technetium, and to confusion between nuclear and electronic spins.
Alternative ground states enable pathway switching in biological electron transfer
Abriata, Luciano A.; Álvarez-Paggi, Damián; Ledesma, Gabriela N.; Blackburn, Ninian J.; Vila, Alejandro J.; Murgida, Daniel H.
2012-01-01
Electron transfer is the simplest chemical reaction and constitutes the basis of a large variety of biological processes, such as photosynthesis and cellular respiration. Nature has evolved specific proteins and cofactors for these functions. The mechanisms optimizing biological electron transfer have been matter of intense debate, such as the role of the protein milieu between donor and acceptor sites. Here we propose a mechanism regulating long-range electron transfer in proteins. Specifically, we report a spectroscopic, electrochemical, and theoretical study on WT and single-mutant CuA redox centers from Thermus thermophilus, which shows that thermal fluctuations may populate two alternative ground-state electronic wave functions optimized for electron entry and exit, respectively, through two different and nearly perpendicular pathways. These findings suggest a unique role for alternative or “invisible” electronic ground states in directional electron transfer. Moreover, it is shown that this energy gap and, therefore, the equilibrium between ground states can be fine-tuned by minor perturbations, suggesting alternative ways through which protein–protein interactions and membrane potential may optimize and regulate electron–proton energy transduction. PMID:23054836
Electronic and ground state properties of ThTe
NASA Astrophysics Data System (ADS)
Bhardwaj, Purvee; Singh, Sadhna
2016-05-01
The electronic properties of ThTe in cesium chloride (CsCl, B2) structure are investigated in the present paper. To study the ground state properties of thorium chalcogenide, the first principle calculations have been calculated. The bulk properties, including lattice constant, bulk modulus and its pressure derivative are obtained. The calculated equilibrium structural parameters are in good agreement with the available experimental and theoretical results.
Two-electron photoionization of ground-state lithium
Kheifets, A. S.; Fursa, D. V.; Bray, I.
2009-12-15
We apply the convergent close-coupling (CCC) formalism to single-photon two-electron ionization of the lithium atom in its ground state. We treat this reaction as single-electron photon absorption followed by inelastic scattering of the photoelectron on a heliumlike Li{sup +} ion. The latter scattering process can be described accurately within the CCC formalism. We obtain integrated cross sections of single photoionization leading to the ground and various excited states of the Li{sup +} ion as well as double photoionization extending continuously from the threshold to the asymptotic limit of infinite photon energy. Comparison with available experimental and theoretical data validates the CCC model.
Calculation of electron scattering from the ground state of ytterbium
Bostock, Christopher J.; Fursa, Dmitry V.; Bray, Igor
2011-05-15
We report on the application of the convergent close-coupling method, in both relativistic and nonrelativistic formulations, to electron scattering from ytterbium. Angle-differential and integrated cross sections are presented for elastic scattering and excitation of the states (6s6p){sup 3}P{sub 0,1,2}, (6s6p){sup 1}P{sub 1}{sup o}, (6s7p){sup 1}P{sub 1}{sup o}, and (6s5d){sup 1}D{sub 2}{sup e} for a range of incident electron energies. We also present calculations of the total cross section, and angle-differential Stokes parameters for excitation of the (6s6p){sup 3}P{sub 1}{sup o} state from the ground state. A comparison is made with the relativistic distorted-wave method and experiments.
NASA Astrophysics Data System (ADS)
Aucar, Ignacio A.; Gómez, Sergio S.; de Azúa, Martín C. Ruiz; Giribet, Claudia G.
2012-05-01
A theoretical study of the relation between the relativistic formulation of the nuclear magnetic shielding and spin-rotation tensors is presented. To this end a theoretical expression of the relativistic spin-rotation tensor is formulated, considering a molecular Hamiltonian of relativistic electrons and non-relativistic nuclei. Molecular rotation effects are introduced considering the terms of the Born-Oppenheimer decomposition, which couple the electrons and nuclei dynamics. The loss of the simple relation linking both spectral parameters in the non-relativistic formulation is further analyzed carrying out a perturbative expansion of relativistic effects by means of the linear response within the elimination of the small component approach. It is concluded that relativistic effects on the spin-rotation tensor are less important than those of the nuclear magnetic shielding tensor.
Electronic ground state properties of Coulomb blockaded quantum dots
NASA Astrophysics Data System (ADS)
Patel, Satyadev Rajesh
Conductance through quantum dots at low temperature exhibits random but repeatable fluctuations arising from quantum interference of electrons. The observed fluctuations follow universal statistics arising from the underlying universality of quantum chaos. Random matrix theory (RMT) has provided an accurate description of the observed universal conductance fluctuations (UCF) in "open" quantum dots (device conductance ≥e 2/h). The focus of this thesis is to search for and decipher the underlying origin of similar universal properties in "closed" quantum dots (device conductance ≤e2/ h). A series of experiments is presented on electronic ground state properties measured via conductance measurements in Coulomb blockaded quantum dots. The statistics of Coulomb blockade (CB) peak heights with zero and non-zero magnetic field measured in various devices agree qualitatively with predictions from Random Matrix Theory (RMT). The standard deviation of the peak height fluctuations for non-zero magnetic field is lower than predicted by RMT; the temperature dependence of the standard deviation of the peak height for non-zero magnetic field is also measured. The second experiment summarizes the statistics of CB peak spacings. The peak spacing distribution width is observed to be on the order of the single particle level spacing, Delta, for both zero and non-zero magnetic field. The ratio of the zero field peak spacing distribution width to the non-zero field peak spacing distribution width is ˜1.2; this is good agreement with predictions from spin-resolved RMT predictions. The standard deviation of the non-zero magnetic field peak spacing distribution width shows a T-1/2 dependence in agreement with a thermal averaging model. The final experiment summarizes the measurement of the peak height correlation length versus temperature for various quantum dots. The peak height correlation length versus temperature saturates in small quantum dots, suggesting spectral scrambling
NASA Astrophysics Data System (ADS)
Farasat, M.; Shojaei, S. H. R.; Morini, F.; Golzan, M. M.; Deleuze, M. S.
2016-04-01
The electronic structure, electron binding energy spectrum and (e, 2e) momentum distributions of aniline have been theoretically predicted at an electron impact energy of 1.500 keV on the basis of Born-Oppenheimer molecular dynamical simulations, in order to account for thermally induced nuclear motions in the initial electronic ground state. Most computed momentum profiles are rather insensitive to thermally induced alterations of the molecular structure, with the exception of the profiles corresponding to two ionization bands at electron binding energies comprised between ˜10.0 and ˜12.0 eV (band C) and between ˜16.5 and ˜20.0 eV (band G). These profiles are found to be strongly influenced by nuclear dynamics in the electronic ground state, especially in the low momentum region. The obtained results show that thermal averaging smears out most generally the spectral fingerprints that are induced by nitrogen inversion.
NASA Astrophysics Data System (ADS)
Nieuwenhuizen, Theodorus M.; Liska, Matthew T. P.
2015-10-01
In a recent paper the authors studied numerically the hydrogen ground state in stochastic electrodynamics (SED) within the the non-relativistic approximation. In quantum theory the leading non-relativistic corrections to the ground state energy dominate the Lamb shift related to the photon cloud that should cause the quantum-like behaviour of SED. The present work takes these corrections into account in the numerical modelling. It is found that they have little effect; the self-ionisation that occurs without them remains present. It is speculated that the point-charge approximation for the electron is the cause of the failure.
Exact many-electron ground states on the diamond Hubbard chain
NASA Astrophysics Data System (ADS)
Gulacsi, Zsolt; Kampf, Arno; Vollhardt, Dieter
2008-03-01
Exact ground states of interacting electrons on the diamond Hubbard chain in a magnetic field are constructed which exhibit a wide range of properties such as flat-band ferromagnetism, correlation induced metallic, half-metallic, or insulating behavior [1]. The properties of these ground states can be tuned by changing the magnetic flux, local potentials, or electron density.The results show that the studied simple one-dimensional structure displays remarkably complex physical properties. The virtue of tuning different ground states through external parameters points to new possibilities for the design of electronic devices which can switch between insulating or conducting and nonmagnetic or (fully or partially spin polarized) ferromagnetic states, open new routes for the design of spin-valve devices and gate induced ferromagnetism. [1] Z. Gulacsi, A. Kampf, D. Vollhardt, Phys. Rev. Lett. 99, 026404(2007).
NASA Astrophysics Data System (ADS)
Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko
2015-10-01
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko
2015-10-01
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing. PMID:26450316
Morini, Filippo; Deleuze, Michael Simon; Watanabe, Noboru; Kojima, Masataka; Takahashi, Masahiko
2015-10-07
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b{sub 1}, 6a{sub 1}, 4b{sub 2}, and 1a{sub 2} orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A{sub 1}, B{sub 1}, and B{sub 2} symmetries, which correspond to C–H stretching and H–C–H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Ground state of a hydrogen ion molecule immersed in an inhomogeneous electron gas
NASA Astrophysics Data System (ADS)
Diaz-Valdes, J.; Gutierrez, F. A.; Matamala, A. R.; Denton, C. D.; Vargas, P.; Valdes, J. E.
2007-01-01
In this work we have calculated the ground state energy of the hydrogen molecule, H2+, immersed in the highly inhomogeneous electron gas around a metallic surface within the local density approximation. The molecule is perturbed by the electron density of a crystalline surface of Au <1 0 0> with the internuclear axis parallel to the surface. The surface spatial electron density is calculated through a linearized band structure method (LMTO-DFT). The ground state of the molecule-ion was calculated using the Born-Oppenheimer approximation for a fixed-ion while the screening effects of the inhomogeneous electron gas are depicted by a Thomas-Fermi like electrostatic potential. We found that within our model the molecular ion dissociates at the critical distance of 2.35 a.u. from the first atomic layer of the solid.
NASA Astrophysics Data System (ADS)
Bödeker, Dietrich; Wörmann, Mirco
2014-02-01
In many phenomenologically interesting models of thermal leptogenesis the heavy neutrinos are non-relativistic when they decay and produce the baryon asymmetry of the Universe. We propose a non-relativistic approximation for the corresponding rate equations in the non-resonant case, and a systematic way for computing relativistic corrections. We determine the leading order coefficients in these equations, and the first relativistic corrections. The non-relativistic approximation works remarkably well. It appears to be consistent with results obtained using a Boltzmann equation taking into account the momentum distribution of the heavy neutrinos, while being much simpler. We also compute radiative corrections to some of the coefficients in the rate equations. Their effect is of order 1% in the regime favored by neutrino oscillation data. We obtain the correct leading order lepton number washout rate in this regime, which leads to large ( ~ 20%) effects compared to previous computations.
A simple, radially correlated ground state wavefunction for two electron atoms.
NASA Technical Reports Server (NTRS)
Altick, P. L.
1972-01-01
A one parameter function is presented as an approximation to the ground state wavefunction of the two electron radial hamiltonian. The parameter may be fixed by a nonvariational criterion. The resulting expectation value of the radial hamiltonian differs from its exact eigenvalue by about 2 parts in 3000 for helium while the 'local energy' never differs by more than 10% from the exact value over the entire r1-r2 plane. The cases Z = 1 and Z = 3 are also investigated.
Kamat, P.V.; Lichtin, N.N.
1981-01-01
Use of thiazine dyes, e.g., thionine and methylene blue, in the conversion of light energy into electrical energy has been studied extensively in recent years. Despite continuing efforts to improve the performance of photogalvanic cells, the highest reported engineering efficiency for photogalvanic conversion of sunlight into electricity is still less than 0.1%. One of the proposed steps to increase efficiency is to employ high concentrations of light-absorbing dye, e.g., 0.1 M. However, use of such high concentrations of dye may lead to wastage of absorbed quantum energy via a variety of processes, one of which is quenching of triplet dye by ground-state dye. A study of such ground-state quenching of protonated triplet methylene blue, /sup 3/MBH/sup 2 +/, with efficiency of net electron transfer in quenching, F/sub 1/, less than 0.5 was reported previously. Quenching without net electron-transfer inevitably reduces the conversion efficiency of photogalvanic cells. The results of a laser flash-photolytic, kinetic spectrometric study of kinetics and mechanism of quenching of protonated triplet thionine, /sup 3/TH/sub 2//sup 2 +/, and /sup 3/MBH/sup 2 +/ by ground-state thionine, TH/sup +/, in water, aqueous CH/sub 3/CN and aqueous ethanol are presented.
Ground state cooling of a nanomechanical resonator using electron transport in hybrid systems
NASA Astrophysics Data System (ADS)
Rastelli, Gianluca; Stadler, Pascal; Belzig, Wolfgang
A still open challenge in nanoelectromechanical systems is the achievement of the quantum regime via active cooling and using electron transport. I will discuss active ground state cooling in a bottom-up device, viz. a carbon nanotube quantum dot suspended between two electric nano-contacts, and for two different coherent transport regimes: (i) spin-polarized current between two ferromagnets and (ii) sub-gap Andreev current between a superconductor and a normal metal. I will show that efficient ground state cooling of the resonator can be achieved for realistic parameters of the system and varying the transport parameters, e.g. gate voltage, magnetic field, etc. Finally I will discuss the signatures in the current-voltage characteristics of the non-equilibrium state of the nanoresonator. Zukunftskolleg of the University of Konstanz; DFG through SFB 767 and BE 3803/5.
Electron excitation from ground state to first excited state: Bohmian mechanics method
NASA Astrophysics Data System (ADS)
Yang, Song; Shuang, Zhao; Fu-Ming, Guo; Yu-Jun, Yang; Su-Yu, Li
2016-03-01
The excitation process of electrons from the ground state to the first excited state via the resonant laser pulse is investigated by the Bohmian mechanics method. It is found that the Bohmian particles far away from the nucleus are easier to be excited and are excited firstly, while the Bohmian particles in the ground state is subject to a strong quantum force at a certain moment, being excited to the first excited state instantaneously. A detailed analysis for one of the trajectories is made, and finally we present the space and energy distribution of 2000 Bohmian particles at several typical instants and analyze their dynamical process at these moments. Project supported by the Doctoral Research Start-up Funding of Northeast Dianli University, China (Grant No. BSJXM-201332), the National Natural Science Foundation of China (Grant Nos. 11547114, 11534004, 11474129, 11274141, 11447192, and 11304116), and the Graduate Innovation Fund of Jilin University, China (Grant No. 2015091).
Excitations of {sup 1}P levels of zinc by electron impact on the ground state
Fursa, Dmitry V.; Bray, Igor; Panajotovic, R.; Sevic, D.; Pejcev, V.; Marinkovic, B.P.; Filipovic, D.M.
2005-07-15
We present results of a joint theoretical and experimental investigation of electron scattering from the 4s{sup 2} {sup 1}S ground state of zinc. The 4s4p {sup 1}P{sup o} and 4s5p {sup 1}P{sup o} differential cross sections were measured at scattering angles between 10 degree sign and 150 degree sign and electron-energies of 15, 20, 25, 40, and 60 eV. Corresponding convergent close-coupling calculations have been performed and are compared with experiment.
Strongly separated pairs of core electrons in computed ground states of small molecules
Gottlieb, Alex D.; Weishäupl, Rada M.
2013-01-01
We have performed full configuration interaction computations of the ground states of the molecules Be, BeH2, Li, LiH, B, and BH and verified that the core electrons constitute “separated electron pairs.” These separated pairs of core electrons have nontrivial structure; the core pair does not simply occupy a single spatial orbital. Our method of establishing the presence of separated electron pairs is direct and conclusive. We do not fit a separated pair model; we work with the wavefunctions of interest directly. To establish that a given group of spin–orbitals contains a quasi-separated pair, we verify by direct computation that the quantum state of the electrons that occupy those spin–orbitals is nearly a pure 2-electron state. PMID:23459686
The use of quadratic forms in the calculation of ground state electronic structures
Keller, Jaime; Weinberger, Peter
2006-08-15
There are many examples in theoretical physics where a fundamental quantity can be considered a quadratic form {rho}={sigma}{sub i}{rho}{sub i}=vertical bar {psi} vertical bar{sup 2} and the corresponding linear form {psi}={sigma}{sub i}{psi}{sub i} is highly relevant for the physical problem under study. This, in particular, is the case of the density and the wave function in quantum mechanics. In the study of N-identical-fermion systems we have the additional feature that {psi} is a function of the 3N configuration space coordinates and {rho} is defined in three-dimensional real space. For many-electron systems in the ground state the wave function and the Hamiltonian are to be expressed in terms of the configuration space (CS), a replica of real space for each electron. Here we present a geometric formulation of the CS, of the wave function, of the density, and of the Hamiltonian to compute the electronic structure of the system. Then, using the new geometric notation and the indistinguishability and equivalence of the electrons, we obtain an alternative computational method for the ground state of the system. We present the method and discuss its usefulness and relation to other approaches.
Electronic Structure and Ground State Properties of Non-Magnetic NiPt Systems
NASA Astrophysics Data System (ADS)
PAUDYAL, DURGA; MOOKERJEE, ABHIJIT
We have studied the electronic properties like density of states and band structures and also the ground state properties like formation energy, cohesive energy, bulk modulus and structural energy of NiPt system using the linearized muffin-tin orbital method introduced by Andersen.1,2 In an earlier communication we had argued that both charge neutrality and scalar relativistic corrections are very important for the high concentration of Pt alloys. The calculations here, were, therefore, carried out with charge neutrality as well as with and without scalar relativistic correction for comparison.
Quantum Cohesion Oscillation of Electron Ground State in Low Temperature Laser Plasma
NASA Technical Reports Server (NTRS)
Zhao, Qingxun; Zhang, Ping; Dong, Lifang; Zhang, Kaixi
1996-01-01
The development of radically new technological and economically efficient methods for obtaining chemical products and for producing new materials with specific properties requires the study of physical and chemical processes proceeding at temperature of 10(exp 3) to 10(exp 4) K, temperature range of low temperature plasma. In our paper, by means of Wigner matrix of quantum statistical theory, a formula is derived for the energy of quantum coherent oscillation of electron ground state in laser plasma at low temperature. The collective behavior would be important in ion and ion-molecule reactions.
Gozem, Samer; Huntress, Mark; Schapiro, Igor; Lindh, Roland; Granovsky, Alexander A; Angeli, Celestino; Olivucci, Massimo
2012-11-13
The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed. PMID:26605574
Magnetic ground state and electronic structure of CeRu(2)Al(10).
Goraus, Jerzy; Ślebarski, Andrzej
2012-03-01
We present a combined theoretical and experimental study of the electronic structure for CeRu(2)Al(10) based on ab initio band structure calculations and x-ray photoemission spectroscopy (XPS) data. Our calculations were performed for the base unit cell and for the hypothetical unit cell which enables antiferromagnetic ordering. The stability of the magnetic phase was investigated within fixed spin moment calculations. When additional 4f correlations are not included in the LSDA C U approach, CeRu(2)Al(10) exhibits an unstable magnetic configuration with the difference in total energy per unit cell between the weakly magnetic state and the non-magnetic one of the order ~0.3 meV. We found that Coulomb correlations among 4f electrons, when they are included in the LSDA C U approach, stabilize the magnetic structure. In the weakly correlated system (small U) an antiferromagnetic (AFM) ground state with the lowest total energy is preferred. The situation is, however, the opposite when the 4f correlations are strong. In this case the ferromagnetic (FM) ground state is preferred. By comparing our calculations with the experimental data we conclude that the 4f correlations in CeRu(2)Al(10) are weak. We also carried out a structural relaxation of atomic positions within the Cmcm unit cell and we found that the Al atoms exhibit noticeable displacement from their positions known from x-ray diffraction (XRD) analysis. PMID:22329993
NASA Astrophysics Data System (ADS)
Borzdov, G. N.
2016-06-01
The fundamental solution of the Dirac equation for an electron in an electromagnetic field with harmonic dependence on space-time coordinates is obtained. The field is composed of three standing plane harmonic waves with mutually orthogonal phase planes and the same frequency. Each standing wave consists of two eigenwaves with different complex amplitudes and opposite directions of propagation. The fundamental solution is obtained in the form of the projection operator defining the subspace of solutions to the Dirac equation. It is illustrated by the analysis of the ground state and the spin precession of the Dirac electron in the field of two counterpropagating plane waves with left and right circular polarizations. Interrelations between the fundamental solution and approximate partial solutions is discussed and a criterion for evaluating the accuracy of approximate solutions is suggested.
Creation of ultracold Sr(2) molecules in the electronic ground state.
Stellmer, Simon; Pasquiou, Benjamin; Grimm, Rudolf; Schreck, Florian
2012-09-14
We report on the creation of ultracold (84)Sr(2) molecules in the electronic ground state. The molecules are formed from atom pairs on sites of an optical lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a transfer efficiency of 30% and obtain 4×10(4) molecules with full control over the external and internal quantum state. STIRAP is performed near the narrow (1)S(0)-(3)P(1) intercombination transition, using a vibrational level of the 1(0(u)(+)) potential as an intermediate state. In preparation of our molecule association scheme, we have determined the binding energies of the last vibrational levels of the 1(0(u)(+)), 1(1(u)) excited-state and the X (1)Σ(g)(+) ground-state potentials. Our work overcomes the previous limitation of STIRAP schemes to systems with magnetic Feshbach resonances, thereby establishing a route that is applicable to many systems beyond alkali-metal dimers. PMID:23005642
Ground-state electronic structure of vanadium(III) trisoxalate in hydrated compounds.
Kittilstved, Kevin R; Sorgho, Lilit Aboshyan; Amstutz, Nahid; Tregenna-Piggott, Philip L W; Hauser, Andreas
2009-08-17
The ground-state electronic structures of K3V(ox)3.3H2O, Na3V(ox)3.5H2O, and NaMgAl1-xVx(ox)3.9H2O (0 < x
Morgada, Marcos N; Abriata, Luciano A; Zitare, Ulises; Alvarez-Paggi, Damian; Murgida, Daniel H; Vila, Alejandro J
2014-06-10
The Cu(A) center is a dinuclear copper site that serves as an optimized hub for long-range electron transfer in heme-copper terminal oxidases. Its electronic structure can be described in terms of a σ(u)* ground-state wavefunction with an alternative, less populated ground state of π(u) symmetry, which is thermally accessible. It is now shown that second-sphere mutations in the Cu(A) containing subunit of Thermus thermophilus ba3 oxidase perturb the electronic structure, which leads to a substantial increase in the population of the π(u) state, as shown by different spectroscopic methods. This perturbation does not affect the redox potential of the metal site, and despite an increase in the reorganization energy, it is not detrimental to the electron-transfer kinetics. The mutations were achieved by replacing the loops that are involved in protein-protein interactions with cytochrome c, suggesting that transient protein binding could also elicit ground-state switching in the oxidase, which enables alternative electron-transfer pathways. PMID:24777732
Electron-impact excitation and ionization cross sections for ground state and excited helium atoms
Ralchenko, Yu. Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de
2008-07-15
Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n{<=}4 are treated individually, while the states with n{>=}5 are considered degenerate. For the processes involving transitions to and from n{>=}5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form.
Electronic transport, density of states and ground state properties of Li In binary alloy
NASA Astrophysics Data System (ADS)
Kumar, Ashwani; Rafique, S. M.; Sinha, T. P.
2008-10-01
The electronic transport properties of Li-In binary alloy have been studied by Harrison's first principle pseudopotential technique. The Percus-Yevik hard sphere model is used to compute the partial structure factors S ij( k) for the alloy at the desired composition. We have also calculated the ground state properties of Li-In alloy employing full-potential linearized augmented plane wave (FLAPW) method. The equilibrium values of bulk modulus and its pressure derivative have been estimated through optimization of the crystal structure of the Li-In alloy. The calculated total density of states (DOS) and the partial DOS around the Fermi energy are used to explain the variation of resistivity of the alloy with carrier concentration.
Levy, Mel E-mail: mlevy@tulane.edu; Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W. E-mail: mlevy@tulane.edu
2014-05-14
Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.
Ground state of bilayer hα-silica: mechanical and electronic properties.
Han, Yang; Hu, Ming
2015-12-18
The family of two-dimensional (2D) crystals was recently joined by silica, one of the most abundant resources on earth. So far two different polymorphs of this material, namely a tetrahedra-shaped monolayer and a fully saturated bilayer structure, have been synthesized on various metal substrates and their fascinating properties enable 2D silica to hold promise in nanoelectronic device applications. In this paper a new ground state of bilayer-AAr-stacking hα-silica-has been discovered by first principles calculations. The new structure is featured with a formation of Si-Si bonds between all sp(3) hybridized SiO3 triangular pyramids, lying respectively in different silica layers, with an intrinsic rotational angle of about 12.5° along the out-of-plane Si-Si bond. Due to the doubled number of Si-Si bonds in the new structure, the system energy is lowered by nearly three times more than that reported recently in literature (0.8 eV) (Özçelik et al 2014 Phys. Rev. Lett. 112 246803), when compared with the single layer hα-silica. A mechanical property investigation shows that the AAr-stacking bilayer hα-silica possesses high in-plane stiffness and a negative Poisson's ratio, which stems from the intrinsic rotational angle of the SiO3 triangular pyramids. Strikingly, the negative Poisson's ratio evolves into positive at a critical tensile strain ϵ ≈ 1.2%. Such negative-to-positive evolvement is associated with the adaptation of the rotational angle to the applied strain and the structure transition into the nearby valley of the energy landscape. The detailed transition process has been thoroughly analyzed. The electronic properties of the new ground state are also calculated, along with their response to the external strain. Our new ground state structure introduces a new member to the family of 2D bilayer silica materials and is expected to facilitate experimental studies identifying the related structures and exploring further physical and chemical properties
Ground state of bilayer hα-silica: mechanical and electronic properties
NASA Astrophysics Data System (ADS)
Han, Yang; Hu, Ming
2015-12-01
The family of two-dimensional (2D) crystals was recently joined by silica, one of the most abundant resources on earth. So far two different polymorphs of this material, namely a tetrahedra-shaped monolayer and a fully saturated bilayer structure, have been synthesized on various metal substrates and their fascinating properties enable 2D silica to hold promise in nanoelectronic device applications. In this paper a new ground state of bilayer—AAr-stacking hα-silica—has been discovered by first principles calculations. The new structure is featured with a formation of Si-Si bonds between all sp3 hybridized SiO3 triangular pyramids, lying respectively in different silica layers, with an intrinsic rotational angle of about 12.5° along the out-of-plane Si-Si bond. Due to the doubled number of Si-Si bonds in the new structure, the system energy is lowered by nearly three times more than that reported recently in literature (0.8 eV) (Özçelik et al 2014 Phys. Rev. Lett. 112 246803), when compared with the single layer hα-silica. A mechanical property investigation shows that the AAr-stacking bilayer hα-silica possesses high in-plane stiffness and a negative Poisson’s ratio, which stems from the intrinsic rotational angle of the SiO3 triangular pyramids. Strikingly, the negative Poisson’s ratio evolves into positive at a critical tensile strain ɛ ≈ 1.2%. Such negative-to-positive evolvement is associated with the adaptation of the rotational angle to the applied strain and the structure transition into the nearby valley of the energy landscape. The detailed transition process has been thoroughly analyzed. The electronic properties of the new ground state are also calculated, along with their response to the external strain. Our new ground state structure introduces a new member to the family of 2D bilayer silica materials and is expected to facilitate experimental studies identifying the related structures and exploring further physical and chemical
NASA Astrophysics Data System (ADS)
Manz, Jörn; Yamamoto, Kentaro
2012-05-01
Unimolecular pericyclic reactions in a non-degenerate electronic ground state proceed under the constraint of zero electronic angular momentum. This restriction engenders a selection rule on the directions of electronic fluxes. Accordingly, clockwise or counter-clockwise fluxes are 'forbidden', whereas pincer-like fluxes (which consist of concerted clockwise and counter-clockwise fluxes) are 'allowed'. The selection rule is illustrated for three reactions: the degenerate Cope rearrangement of hexadiene, hydrogen transfer in malonaldehyde, and double proton transfer in the formic acid dimer.
Electronic excitation of ground state atoms by collision with heavy gas particles
NASA Technical Reports Server (NTRS)
Hansen, C. Frederick
1993-01-01
Most of the important chemical reactions which occur in the very high temperature air produced around space vehicles as they enter the atmosphere were investigated both experimentally and theoretically, to some extent at least. One remaining reaction about which little is known, and which could be quite important at the extremely high temperatures that will be produced by the class of space vehicles now contemplated - such as the AOTV - is the excitation of bound electron states due to collisions between heavy gas particles. Rates of electronic excitation due to free electron collisions are known to be very rapid, but because these collisions quickly equilibrate the free and bound electron energy, the approach to full equilibrium with the heavy particle kinetic energy will depend primarily on the much slower process of bound electron excitation in heavy particle collisions and the subsequent rapid transfer to free electron energy. This may be the dominant mechanism leading to full equilibrium in the gas once the dissociation process has depleted the molecular states so the transfer between molecular vibrational energy and free electron energy is no longer available as a channel for equilibration of free electron and heavy particle kinetic energies. Two mechanisms seem probable in electronic excitation by heavy particle impact. One of these is the collision excitation and deexcitation of higher electronic states which are Rydberg like. A report, entitled 'Semi-Classical Theory of Electronic Excitation Rates', was submitted previously. This presented analytic expressions for the transition probabilities, assuming that the interaction potential is an exponential repulsion with a perturbation ripple due to the dipole-induced dipole effect in the case of neutral-neutral collisions, and to the ion-dipole interaction in the case of ion-neutral collisions. However the above may be, there is little doubt that excitation of ground state species by collision occurs at the
Electronic structure and ground-state properties of Na{sub 2}Po: A first-principles study
Eithiraj, R. D.
2015-06-24
Self-consistent scalar-relativistic band structure calculations have been performed to investigate the electronic structure and ground-state properties of Na{sub 2}Po in cubic antifluorite (anti-CaF{sub 2}-type) structure using the linear muffin-tin orbital in its tight-binding representation (TB-LMTO) method. Ground state properties such as equilibrium lattice constant and bulk modulus were calculated. The results of the electronic structure calculations show that Na{sub 2}Po is direct bandgap semiconductor.
Theoretical study of the electronic ground state of iron(II) porphine. II
NASA Astrophysics Data System (ADS)
Choe, Yoong-Kee; Nakajima, Takahito; Hirao, Kimihiko; Lindh, Roland
1999-09-01
Ten low-lying electronic states of Fe(II) porphine, 5A1g, 5Eg, 5B2g, 3A2g, 3B2g, 3Eg(A), 3Eg(B), 1A1g, 1B2g, and 1Eg states, are studied with multiconfigurational second-order perturbation (CASPT2) calculations with complete active space self-consistent field (CASSCF) reference functions with larger active space and basis sets. The enlargement of active space and basis sets has no influence on the conclusion of a previous multireference Møller-Plesset perturbation (MRMP) study. The present CASPT2 calculation concludes that the 5A1g state is the ground state. A relativistic correction has been performed by the relativistic scheme of eliminating small components (RESC). For energetics, no significant contribution from the relativistic correction was found. The relative energies and orbital energies are not changed appreciably by the introduction of a relativistic correction. The present result does not agree with all the spectroscopic observations, but is consistent with a magnetic moment study.
NASA Astrophysics Data System (ADS)
Amovilli, C.; March, N. H.
The recent study by Joubert on effects of Coulomb repulsions in a many-electron system has focused attention on an integral identity involving the pair density. This has motivated the derivation presented here of a vectorial differential form related to this integral result. Our differential identity is then illustrated explicitly by using (i) an exact ground-state wave function for the so-called Hookean atom having external potential energy (1/2)kr2, with k = 1/4, and (ii) Moshinsky's model in which both the interparticle interaction and the external potential are of harmonic type.
ERIC Educational Resources Information Center
Bandyopadhyay, Subhajit; Roy, Saswata
2014-01-01
This paper describes an inexpensive experiment to determine the carbonyl stretching frequency of an organic keto compound in its ground state and first electronic excited state. The experiment is simple to execute, clarifies some of the fundamental concepts of spectroscopy, and is appropriate for a basic spectroscopy laboratory course. The…
NASA Astrophysics Data System (ADS)
Yurchenko, Sergei N.; Carvajal, Miguel; Thiel, Walter; Jensen, Per
2006-09-01
We report a six-dimensional CCSD(T)/aug-cc-pVTZ dipole moment surface for the electronic ground state of PH 3 computed ab initio on a large grid of 10 080 molecular geometries. Parameterized, analytical functions are fitted through the ab initio data, and the resulting dipole moment functions are used, together with a potential energy function determined by refining an existing ab initio surface in fittings to experimental wavenumber data, for simulating absorption spectra of the first three polyads of PH 3, i.e., ( ν2, ν4), ( ν1, ν3, 2 ν2, 2 ν4, ν2 + ν4), and ( ν1 + ν2, ν3 + ν2, ν1 + ν4, ν3 + ν4, 2 ν2 + ν4, ν2 + 2 ν4, 3 ν2, 3 ν4). The resulting theoretical transition moments show excellent agreement with experiment. A line-by-line comparison of the simulated intensities of the ν2/ ν4 band system with 955 experimental intensity values reported by Brown et al. [L.R. Brown, R.L. Sams, I. Kleiner, C. Cottaz, L. Sagui, J. Mol. Spectrosc. 215 (2002) 178-203] gives an average absolute percentage deviation of 8.7% (and a root-mean-square deviation of 0.94 cm -1 for the transition wavenumbers). This is very remarkable since the calculations rely entirely on ab initio dipole moment surfaces and do not involve any adjustment of these surfaces to reproduce the experimental intensities. Finally, we predict the line strengths for transitions between so-called cluster levels (near-degenerate levels formed at high rotational excitation) for J up to 60.
The Doping Dependence of the Ground State in the Electron-doped Cuprates
NASA Astrophysics Data System (ADS)
Greene, Richard L.
2004-03-01
The mechanism behind high-temperature superconductivity in the cuprates is not yet determined. Understanding the nature of the normal ground state at various dopings is important for the ultimate determination of the mechanism. Some theories suggest that excitations associated with a doping-dependent quantum phase transition (QPT) are an essential ingredient. So far the evidence for a QPT in the cuprates has been indirect and inconclusive. The electron-doped cuprates offer a distinct advantage over their hole-doped counterparts because the maximum critical magnetic field (H_c2) necessary to access the T=0 normal state is less than 10T. Here, I will present comprehensive measurements of the low-temperature (0.35K to 20K) ab-plane resistivity and Hall effect in the normal state (H>H_c2) of the electron-doped cuprate Pr_2-xCe_xCuO4 (PCCO) as a function of Ce doping. These measurements [1] strongly suggest a quantum critical point at x_c=0.165±0.005 with an associated quantum fluctuation regime at higher temperatures and at nearby dopings. I will also present tunneling results which show that a normal state pseudogap, of unknown origin, disappears near the same doping [2]. The nature of the QPT cannot be determined from our measurements but other results [3] on PCCO suggest an antiferromagnetic-metal to paramagnetic- metal phase transition. I will also report low-temperature specific heat and Raman scattering data in the superconducting state, which show that the superconducting gap anisotropy changes near the critical doping x_c. [1] Y. Dagan et al., cond-mat/0310475. [2] A. Biswas et al., Phys. Rev. B64, 104519 (2001); L. Alff et al., Nature 422, 698 (2003. [3] J. Sonier et al., Phys. Rev. Lett. 91, 147002 (2003); M. Fujita et al., cond-mat/0311269. In collaboration with Y. Dagan, H. Balci, G. Blumberg, C. Kendziora, and M.M.Qazilbash. Support from the NSF under DMR-0102350.
Loco, Daniele; Polack, Étienne; Caprasecca, Stefano; Lagardère, Louis; Lipparini, Filippo; Piquemal, Jean-Philip; Mennucci, Benedetta
2016-08-01
A fully polarizable implementation of the hybrid quantum mechanics/molecular mechanics approach is presented, where the classical environment is described through the AMOEBA polarizable force field. A variational formalism, offering a self-consistent relaxation of both the MM induced dipoles and the QM electronic density, is used for ground state energies and extended to electronic excitations in the framework of time-dependent density functional theory combined with a state specific response of the classical part. An application to the calculation of the solvatochromism of the pyridinium N-phenolate betaine dye used to define the solvent ET(30) scale is presented. The results show that the QM/AMOEBA model not only properly describes specific and bulk effects in the ground state but it also correctly responds to the large change in the solute electronic charge distribution upon excitation. PMID:27340904
NASA Astrophysics Data System (ADS)
Korona, Tatiana
2012-02-01
A possibility to calculate electron affinities (EAs) by a software devised for electron excitations is exploited to examine the accuracy of a partly local EA-EOM-CCSD method. In the proposed approach local approximations are applied to the ground-state coupled cluster wave function, while the EAs themselves are obtained in a full configurational space. The results of a numerical test for 14 molecules show that already with standard local settings the method reproduces the nonlocal EAs with the average error of 0.009 eV. Since the EA-EOM step of the calculation requires less computational resources than the computation of the CCSD ground state, the proposed hybrid approach can become a valuable tool for obtaining the EAs for molecules, which are too large for a canonical CCSD calculation, but still small enough for the EA-EOM step to be performed in a nonlocal way.
Exact ground state for the four-electron problem in a 2D finite honeycomb lattice
NASA Astrophysics Data System (ADS)
Trencsényi, Réka; Glukhov, Konstantin; Gulácsi, Zsolt
2014-07-01
Working in a subspace with dimensionality much smaller than the dimension of the full Hilbert space, we deduce exact four-particle ground states in 2D samples containing hexagonal repeat units and described by Hubbard type of models. The procedure identifies first a small subspace ? in which the ground state ? is placed, than deduces ? by exact diagonalization in ?. The small subspace is obtained by the repeated application of the Hamiltonian ? on a carefully chosen starting wave vector describing the most interacting particle configuration, and the wave vectors resulting from the application of ?, till the obtained system of equations closes in itself. The procedure which can be applied in principle at fixed but arbitrary system size and number of particles is interesting on its own since it provides exact information for the numerical approximation techniques which use a similar strategy, but apply non-complete basis for ?. The diagonalization inside ? provides an incomplete image of the low lying part of the excitation spectrum, but provides the exact ?. Once the exact ground state is obtained, its properties can be easily analysed. The ? is found always as a singlet state whose energy, interestingly, saturates in the ? limit. The unapproximated results show that the emergence probabilities of different particle configurations in the ground state presents 'Zittern' (trembling) characteristics which are absent in 2D square Hubbard systems. Consequently, the manifestation of the local Coulomb repulsion in 2D square and honeycomb types of systems presents differences, which can be a real source in the differences in the many-body behaviour.
NASA Astrophysics Data System (ADS)
Fischer, Ingo; Lochschmidt, Andreas; Strobel, Andreas; Niedner-Schatteburg, Gereon; Mueller-Dethlefs, Klaus; Bondybey, Vladimir E.
1993-03-01
Zero kinetic energy photoelectron spectra from the electronic ground state of hydrogen sulfide are obtained via nonresonant two-photon ionization with complete rotational resolution in the ion. The two-photon spectra are compared with those recently obtained via one-photon VUV photoionization. The spectra show a close similarity, but type a transitions in the two-photon spectra are twice as intense.
Influence of electron doping on the ground state of (Sr1 -xLax)2IrO4
NASA Astrophysics Data System (ADS)
Chen, Xiang; Hogan, Tom; Walkup, D.; Zhou, Wenwen; Pokharel, M.; Yao, Mengliang; Tian, Wei; Ward, Thomas Z.; Zhao, Y.; Parshall, D.; Opeil, C.; Lynn, J. W.; Madhavan, Vidya; Wilson, Stephen D.
2015-08-01
The evolution of the electronic properties of electron-doped (Sr1 -xLax)2IrO4 is experimentally explored as the doping limit of La is approached. As electrons are introduced, the electronic ground-state transitions from a spin-orbit Mott phase into an electronically phase separated state, where long-range magnetic order vanishes beyond x =0.02 and charge transport remains percolative up to the limit of La substitution (x ≈0.06 ). In particular, the electronic ground state remains inhomogeneous even beyond the collapse of the parent state's long-range antiferromagnetic order, while persistent short-range magnetism survives up to the highest La-substitution levels. Furthermore, as electrons are doped into Sr2IrO4 , we observe the appearance of a low-temperature magnetic glasslike state intermediate to the complete suppression of antiferromagnetic order. Universalities and differences in the electron-doped phase diagrams of single-layer and bilayer Ruddlesden-Popper strontium iridates are discussed.
Influence of electron doping on the ground state of (Sr1-xLax)2IrO4
Chen, Xiang; Hogan, Tom; Walkup, D.; Zhou, Wenwen; Pokharel, M.; Yao, Mengliang; Tian, Wei; Ward, Thomas Zac; Zhao, Y.; Parshall, Dr. D.; et al
2015-08-17
The evolution of the electronic properties of electron-doped (Sr1-xLax)2IrO4 is experimentally explored as the doping limit of La is approached. As electrons are introduced, the electronic ground state transitions from a spin-orbit Mott phase into an electronically phase separated state, where long-range magnetic order vanishes beyond x = 0:02 and charge transport remains percolative up to the limit of La substitution (x =0:06). In particular, the electronic ground state remains inhomogeneous even beyond the collapse of the parent state's long-range antiferromagnetic order, while persistent short-range magnetism survives up to the highest La-substitution levels. Furthermore, as electrons are doped into Sr2IrO4,more » we observe the appearance of a low temperature magnetic glass-like state intermediate to the complete suppression of antiferromagnetic order. Universalities and di erences in the electron-doped phase diagrams of single layer and bilayer Ruddlesden-Popper strontium iridates are discussed.« less
NASA Astrophysics Data System (ADS)
Beyer, Maximilian; Merkt, Frédéric
2016-03-01
Although the existence of quasibound rotational levels of the X+ 2Σg+ ground state of H2+ was predicted a long time ago, these states have never been observed. Calculated positions and widths of quasibound rotational levels located close to the top of the centrifugal barriers have not been reported either. Given the role that such states play in the recombination of H (1 s ) and H+ to form H2+, this lack of data may be regarded as one of the largest unknown aspects of this otherwise accurately known fundamental molecular cation. We present measurements of the positions and widths of the lowest-lying quasibound rotational levels of H2+ and compare the experimental results with the positions and widths we calculate using a potential model for the X+ state of H2+ which includes adiabatic, nonadiabatic, relativistic, and radiative corrections to the Born-Oppenheimer approximation.
Cubrovic, Mihailo; Liu Yan; Schalm, Koenraad; Sun Yawen; Zaanen, Jan
2011-10-15
We argue that the electron star and the anti-de Sitter (AdS) Dirac hair solution are two limits of the free charged Fermi gas in AdS. Spectral functions of holographic duals to probe fermions in the background of electron stars have a free parameter that quantifies the number of constituent fermions that make up the charge and energy density characterizing the electron star solution. The strict electron star limit takes this number to be infinite. The Dirac hair solution is the limit where this number is unity. This is evident in the behavior of the distribution of holographically dual Fermi surfaces. As we decrease the number of constituents in a fixed electron star background the number of Fermi surfaces also decreases. An improved holographic Fermi ground state should be a configuration that shares the qualitative properties of both limits.
Non-Relativistic Superstring Theories
Kim, Bom Soo
2007-12-14
We construct a supersymmetric version of the 'critical' non-relativistic bosonic string theory [1] with its manifest global symmetry. We introduce the anticommuting bc CFT which is the super partner of the {beta}{gamma} CFT. The conformal weights of the b and c fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider 'noncritical' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.
David R. Farley
2010-08-19
A model has been developed to calculate the ground-state rotational populations of homonuclear diatomic molecules in kinetic gases, including the effects of electron-impact excitation, wall collisions, and gas feed rate. The equations are exact within the accuracy of the cross sections used and of the assumed equilibrating effect of wall collisions. It is found that the inflow of feed gas and equilibrating wall collisions can significantly affect the rotational distribution in competition with non-equilibrating electron-impact effects. The resulting steady-state rotational distributions are generally Boltzmann for N≥3, with a rotational temperature between the wall and feed gas temperatures. The N=0,1,2 rotational level populations depend sensitively on the relative rates of electron-impact excitation versus wall collision and gas feed rates.
NASA Astrophysics Data System (ADS)
Nawa, Kenji; Kitaoka, Yukie; Nakamura, Kohji; Imamura, Hiroshi; Akiyama, Toru; Ito, Tomonori; Weinert, M.
2016-07-01
The ground-state electronic configurations of the correlated organometallic metallocenes, M Cp2,M =V , Cr, Mn, Fe, Co, and Ni, are investigated using constraint density functional theory combined with nonempirical Ueff parameters determined from linear-response theory. The relative stability of the various d -orbital electronic configurations of these organometallic molecules is found to be sensitive to the amount of correlation. Using nonempirical values of Ueff, the calculated electronic configurations are in agreement with the experiments: 4A2 g ,3E2 g ,6A1 g ,1A1 g ,2E1 g , and 3A2 g for the VCp2,CrCp2,MnCp2,FeCp2,CoCp2 , and NiCp2, respectively.
NASA Astrophysics Data System (ADS)
Kuhn, Bernd; Rizzo, Thomas R.; Luckhaus, David; Quack, Martin; Suhm, Martin A.
1999-08-01
We report calculations of the electronic ground state potential energy surface (PES) of hydrogen peroxide covering, in an almost global fashion, all six internal degrees of freedom by two different ab initio techniques. Density functional theory (DFT) calculations using the Becke 3 parameter Lee-Yang-Parr (B3LYP) hybrid functional and multiconfigurational second order perturbation theory (CASPT2) calculations, both using large basis sets, are performed for a wide range of geometries (8145 DFT and 5310 CASPT2 single-point energies). We use a combined data set of mostly DFT with additional CASPT2 ab initio points and the complete CASPT2 surface to fit a total of four different 6D analytical representations. The resulting potentials contain 70-76 freely adjusted parameters and represent the ground state PES up to 40000 cm-1 above the equilibrium energy with a standard deviation of 100-107 cm-1 without any important artifacts. One of the model surfaces is further empirically refined to match the bond dissociation energy D0 for HOOH→2OH . The potentials are designed for energy regions accessible by vibrational fundamental and overtone spectroscopy including the dissociation channel into hydroxyl radicals. Characteristic properties of the model surfaces are investigated by means of stationary point analyses, torsional barrier heights, harmonic frequencies, low-dimensional cuts and minimum energy paths for dissociation. Overall good agreement with high-level ab initio calculations, especially for the CASPT2 based potentials, is achieved. The drastic change in geometry at intermediate O-O distances, which reflects the transition from covalent to hydrogen bonding, is reproduced quantitatively. We calculate fully 6D anharmonic zero point energies and ground state torsional splittings with the diffusion quantum Monte Carlo method in perfect agreement, within statistical error bars, with experiment for the CASPT2 based potentials. Variational vibrational calculations in the
NASA Astrophysics Data System (ADS)
Aimi, Takeshi; Imada, Masatoshi
2007-08-01
We examine Gaussian-basis Monte Carlo (GBMC) method introduced by Corney and Drummond. This method is based on an expansion of the density-matrix operator \\hatρ by means of the coherent Gaussian-type operator basis \\hatΛ and does not suffer from the minus sign problem. The original method, however, often fails in reproducing the true ground state and causes systematic errors of calculated physical quantities because the samples are often trapped in some metastable or symmetry broken states. To overcome this difficulty, we combine the quantum-number projection scheme proposed by Assaad, Werner, Corboz, Gull, and Troyer in conjunction with the importance sampling of the original GBMC method. This improvement allows us to carry out the importance sampling in the quantum-number-projected phase-space. Some comparisons with the previous quantum-number projection scheme indicate that, in our method, the convergence with the ground state is accelerated, which makes it possible to extend the applicability and widen the range of tractable parameters in the GBMC method. The present scheme offers an efficient practical way of computation for strongly correlated electron systems beyond the range of system sizes, interaction strengths and lattice structures tractable by other computational methods such as the quantum Monte Carlo method.
Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Covinsky, M.H.; Lee, Y.T. )
1991-04-18
The reactions of ground- and excited-state Na atoms with methyl bromide (CH{sub 3}Br) and chlorine (Cl{sub 2}) have been studied by using the crossed molecular beams method. For both reactions, the cross sections increase with increasing electronic energy. The product recoil energies change little with increasing Na electronic energy, implying that the product internal energies increase substantially. For Na + CH{sub 3}Br, the steric angle of acceptance opens with increasing electronic energy.
NASA Astrophysics Data System (ADS)
Säkkinen, Niko; Peng, Yang; Appel, Heiko; van Leeuwen, Robert
2015-12-01
We study ground-state properties of a two-site, two-electron Holstein model describing two molecules coupled indirectly via electron-phonon interaction by using both exact diagonalization and self-consistent diagrammatic many-body perturbation theory. The Hartree and self-consistent Born approximations used in the present work are studied at different levels of self-consistency. The governing equations are shown to exhibit multiple solutions when the electron-phonon interaction is sufficiently strong, whereas at smaller interactions, only a single solution is found. The additional solutions at larger electron-phonon couplings correspond to symmetry-broken states with inhomogeneous electron densities. A comparison to exact results indicates that this symmetry breaking is strongly correlated with the formation of a bipolaron state in which the two electrons prefer to reside on the same molecule. The results further show that the Hartree and partially self-consistent Born solutions obtained by enforcing symmetry do not compare well with exact energetics, while the fully self-consistent Born approximation improves the qualitative and quantitative agreement with exact results in the same symmetric case. This together with a presented natural occupation number analysis supports the conclusion that the fully self-consistent approximation describes partially the bipolaron crossover. These results contribute to better understanding how these approximations cope with the strong localizing effect of the electron-phonon interaction.
Säkkinen, Niko; Leeuwen, Robert van; Peng, Yang; Appel, Heiko
2015-12-21
We study ground-state properties of a two-site, two-electron Holstein model describing two molecules coupled indirectly via electron-phonon interaction by using both exact diagonalization and self-consistent diagrammatic many-body perturbation theory. The Hartree and self-consistent Born approximations used in the present work are studied at different levels of self-consistency. The governing equations are shown to exhibit multiple solutions when the electron-phonon interaction is sufficiently strong, whereas at smaller interactions, only a single solution is found. The additional solutions at larger electron-phonon couplings correspond to symmetry-broken states with inhomogeneous electron densities. A comparison to exact results indicates that this symmetry breaking is strongly correlated with the formation of a bipolaron state in which the two electrons prefer to reside on the same molecule. The results further show that the Hartree and partially self-consistent Born solutions obtained by enforcing symmetry do not compare well with exact energetics, while the fully self-consistent Born approximation improves the qualitative and quantitative agreement with exact results in the same symmetric case. This together with a presented natural occupation number analysis supports the conclusion that the fully self-consistent approximation describes partially the bipolaron crossover. These results contribute to better understanding how these approximations cope with the strong localizing effect of the electron-phonon interaction.
Inelastic electron tunneling through degenerate and nondegenerate ground state polymeric junctions
NASA Astrophysics Data System (ADS)
Golsanamlou, Z.; Bagheri Tagani, M.; Rahimpour Soleimani, H.
2015-05-01
The inelastic electron transport properties through two polymeric (trans-polyacetylene and polythiophene) molecular junctions are studied using Keldysh nonequilibrium Green function formalism. The Hamiltonian of the polymers is described via Su-Schrieffer-Heeger model and the metallic electrodes are modeled by the wide-band approximation. Results show that the step-like behavior of the current-voltage characteristics is deformed in presence of strong electron-phonon interaction. Also, the magnitude of current is slightly decreased in the phonon assistant electron transport regime. In addition, it is observed that the I-V curves are independent of temperature.
NASA Astrophysics Data System (ADS)
Patil, S. H.; Tang, K. T.; Toennies, J. P.
1999-10-01
Simple analytical wave functions satisfying appropriate boundary conditions are constructed for the ground states of one-and two-electron homonuclear molecules. Both the asymptotic condition when one electron is far away and the cusp condition when the electron coalesces with a nucleus are satisfied by the proposed wave function. For H2+, the resulting wave function is almost identical to the Guillemin-Zener wave function which is known to give very good energies. For the two electron systems H2 and He2++, the additional electron-electron cusp condition is rigorously accounted for by a simple analytic correlation function which has the correct behavior not only for r12→0 and r12→∞ but also for R→0 and R→∞, where r12 is the interelectronic distance and R, the internuclear distance. Energies obtained from these simple wave functions agree within 2×10-3 a.u. with the results of the most sophisticated variational calculations for all R and for all systems studied. This demonstrates that rather simple physical considerations can be used to derive very accurate wave functions for simple molecules thereby avoiding laborious numerical variational calculations.
Non-relativistic s-wave binding energies of Λ-particle in hypernuclei
NASA Astrophysics Data System (ADS)
Armat, A.; Hassanabadi, H.
2016-04-01
In this work, the ground state binding energy of Λ-particle in hypernuclei is investigated by using analytical solution of non-relativistic Schrödinger equation in the presence of a generalized Woods-Saxon-type interaction. The comparison with the experimental data is motivating.
Badri, Zahra; Foroutan-Nejad, Cina
2016-04-28
In the present account we investigate a theoretical link between the bond length, electron sharing, and bond energy within the context of quantum chemical topology theories. The aromatic stabilization energy, ASE, was estimated from this theoretical link without using isodesmic reactions for the first time. The ASE values obtained from our method show a meaningful correlation with the number of electrons contributing to the aromaticity. This theoretical link demonstrates that structural, electronic, and energetic criteria of aromaticity - ground-state aromaticity - belong to the same class and guarantees that they assess the same property as aromaticity. Theory suggests that interatomic exchange-correlation potential, obtained from the theory of Interacting Quantum Atoms (IQA), is linearly connected to the delocalization index of Quantum Theory of Atoms in Molecules (QTAIM) and the bond length through a first order approximation. Our study shows that the relationship between energy, structure and electron sharing marginally deviates from the ideal linear form expected from the first order approximation. The observed deviation from linearity was attributed to a different contribution of exchange-correlation to the bond energy for the σ- and π-frameworks. Finally, we proposed two-dimensional energy-structure-based aromaticity indices in analogy to the electron sharing indices of aromaticity. PMID:26678719
Non-relativistic scale anomalies
NASA Astrophysics Data System (ADS)
Arav, Igal; Chapman, Shira; Oz, Yaron
2016-06-01
We extend the cohomological analysis in arXiv:1410.5831 of anisotropic Lifshitz scale anomalies. We consider non-relativistic theories with a dynamical critical exponent z = 2 with or without non-relativistic boosts and a particle number symmetry. We distinguish between cases depending on whether the time direction does or does not induce a foliation structure. We analyse both 1 + 1 and 2 + 1 spacetime dimensions. In 1 + 1 dimensions we find no scale anomalies with Galilean boost symmetries. The anomalies in 2 + 1 dimensions with Galilean boosts and a foliation structure are all B-type and are identical to the Lifshitz case in the purely spatial sector. With Galilean boosts and without a foliation structure we find also an A-type scale anomaly. There is an infinite ladder of B-type anomalies in the absence of a foliation structure with or without Galilean boosts. We discuss the relation between the existence of a foliation structure and the causality of the field theory.
Komasa, J; Słupski, R; Jankowski, K; Wasilewski, J; Teale, A M
2013-04-28
Benchmark results for electron densities in the ground states of Li(-), Be, C(2+), Ne(6+), and Ar(14+) have been generated from very accurate variational wave functions represented in terms of extensive basis sets of exponentially correlated Gaussian functions. For Ne(6+), and Ar(14+), the upper bounds to the energies improve over previous results known from the literature. For the remaining systems our bounds are from 0.1 to 1.1 μhartree higher than the most accurate ones. We present in graphical and, partially, numerical form results both for the radial electron densities and for the difference radial density distributions (DRD) (defined with respect to the Hartree-Fock radial density) that highlight the impact of correlation effects on electron densities. Next, we have employed these DRD distributions in studies of the performance of several broadly used orbital-based quantum-chemical methods in accounting for correlation effects on the density. Our computed benchmark densities for Be have been also applied for testing the possibility of using the mathematically strict result concerning exact atomic electron densities, obtained by Ahlrichs et al. [Phys. Rev. A 23, 2106 (1981)], for the determination of the reliability range of computed densities in the long-range asymptotic region. The results obtained for Be are encouraging. PMID:23635137
High accuracy ab initio studies of electron-densities for the ground state of Be-like atomic systems
NASA Astrophysics Data System (ADS)
Komasa, J.; Słupski, R.; Jankowski, K.; Wasilewski, J.; Teale, A. M.
2013-04-01
Benchmark results for electron densities in the ground states of Li-, Be, C2+, Ne6+, and Ar14+ have been generated from very accurate variational wave functions represented in terms of extensive basis sets of exponentially correlated Gaussian functions. For Ne6+, and Ar14+, the upper bounds to the energies improve over previous results known from the literature. For the remaining systems our bounds are from 0.1 to 1.1 μhartree higher than the most accurate ones. We present in graphical and, partially, numerical form results both for the radial electron densities and for the difference radial density distributions (DRD) (defined with respect to the Hartree-Fock radial density) that highlight the impact of correlation effects on electron densities. Next, we have employed these DRD distributions in studies of the performance of several broadly used orbital-based quantum-chemical methods in accounting for correlation effects on the density. Our computed benchmark densities for Be have been also applied for testing the possibility of using the mathematically strict result concerning exact atomic electron densities, obtained by Ahlrichs et al. [Phys. Rev. A 23, 2106 (1981), 10.1103/PhysRevA.23.2106], for the determination of the reliability range of computed densities in the long-range asymptotic region. The results obtained for Be are encouraging.
NASA Astrophysics Data System (ADS)
Vlček, Vojtěch; Steinle-Neumann, Gerd; Leppert, Linn; Armiento, Rickard; Kümmel, Stephan
2015-01-01
A recently published generalized gradient approximation functional within density functional theory (DFT) has shown, in a few paradigm tests, an improved KS orbital description over standard (semi)local approximations. The characteristic feature of this functional is an enhancement factor that diverges like s ln(s ) for large reduced density gradients s which leads to unusual properties. We explore the improved orbital description of this functional more thoroughly by computing the electronic band structure, band gaps, and the optical dielectric constants in semiconductors, Mott insulators, and ionic crystals. Compared to standard semilocal functionals, we observe improvement in both the band gaps and the optical dielectric constants. In particular, the results are similar to those obtained with orbital functionals or by perturbation theory methods in that it opens band gaps in systems described as metallic by standard (semi)local density functionals, e.g., Ge, α -Sn, and CdO.
Kamat, P.V.; Lichtin, N.N.
1981-04-02
A Q-switched pulsed ruby laser emitting at 694.3 nm was used in an investigation by means of flash photolysis-kinetic spectrophotometry of the mechanism of quenching of the monoprotonated lowest triplet state of methylene blue, /sup 3/MBH/sup 2 +/, by the ground state of the dye, MB/sup +/. Quenching in 0.01 N acid is accompanied by electron transfer to give the half-oxidized and half-reduced ion radicals, MB/sup 2 +/. and MBH/sup +/.. The absorption spectrum of MB/sup 2 +/. has been characterized in several media from 360 to 600 nm. The rate constant for quenching, k/sub q/, varies with solvent, ionic strength, and nature of anions with values around 1 x 10/sup 8/ M/sup -1/ s/sup -1/ in water, aqueous CH/sub 3/CN, and aqueous EtOH. The efficiency of net electron transfer in quenching, F/sub 1/(= k/sub et//k/sub q/), varies with solvent but is independent of the ionic strength or the nature of the anions. F/sub 1/ varies inversely with polarity of the solvent from 0.055 in water to 0.48 in 90% (vol/vol) aqueous CH/sub 3/CN. On the basis of analogy to the behavior of a number of other quenchers and the observed linear variation of the function ln ((1/F/sub 1/)-1) with Kosower's polarity parameter Z, it is suggested that reversible electron transfer is the only significant mechanism of quenching of /sup 3/MBH/sup 2 +/ by MB/sup +/(S/sub 0/). Both MBH/sup +/. and MB/sup 2 +/. decay by second-order processes in solvents containing 75% (vol/vol) or less of organic component but the specific rates are different for the two species in most media. It is suggested that in the latter media both cross reaction of MBH/sup +/. with MB/sup 2 +/. and biomolecular reaction of two molecules of the same radical occur. This study shows that ground-state quenching can significantly reduce the sunlight engineering efficency of photogalvanic conversion in systems incorporating relatively concentrated dyes.
Egorova, Dassia
2015-06-07
Several recent experiments report on possibility of dark-state detection by means of so called beating maps of two-dimensional photon-echo spectroscopy [Ostroumov et al., Science 340, 52 (2013); Bakulin et al., Ultrafast Phenomena XIX (Springer International Publishing, 2015)]. The main idea of this detection scheme is to use coherence induced upon the laser excitation as a very sensitive probe. In this study, we investigate the performance of ground-state coherence in the detection of dark electronic states. For this purpose, we simulate beating maps of several models where the excited-state coherence can be hardly detected and is assumed not to contribute to the beating maps. The models represent strongly coupled electron-nuclear dynamics involving avoided crossings and conical intersections. In all the models, the initially populated optically accessible excited state decays to a lower-lying dark state within few hundreds femtoseconds. We address the role of Raman modes and of interstate-coupling nature. Our findings suggest that the presence of low-frequency Raman active modes significantly increases the chances for detection of dark states populated via avoided crossings, whereas conical intersections represent a more challenging task.
Comments on variational ground states for lattice hamiltonians
NASA Astrophysics Data System (ADS)
Anishetty, Ramesh; Bovier, Anton
1984-02-01
We find that the nearest neighbour Jastrow type ground state cannot yield a Lorentz invariant vacuum in the continuum. This is explicitly demonstrated for the chiral model in 1+1 dimensions. The Jastrow ground state is found to be an exact ground state of a new hamiltonian which differs from the original by seemingly ``irrelevant terms'' at the continuum. However these terms prevent the restoration of Lorentz invariance. Finally we speculate that the new hamiltonian can be a non-relativistic approximation with galilean invariance.
Ab initio non-relativistic spin dynamics
Ding, Feizhi; Goings, Joshua J.; Li, Xiaosong; Frisch, Michael J.
2014-12-07
Many magnetic materials do not conform to the (anti-)ferromagnetic paradigm where all electronic spins are aligned to a global magnetization axis. Unfortunately, most electronic structure methods cannot describe such materials with noncollinear electron spin on account of formally requiring spin alignment. To overcome this limitation, it is necessary to generalize electronic structure methods and allow each electron spin to rotate freely. Here, we report the development of an ab initio time-dependent non-relativistic two-component spinor (TDN2C), which is a generalization of the time-dependent Hartree-Fock equations. Propagating the TDN2C equations in the time domain allows for the first-principles description of spin dynamics. A numerical tool based on the Hirshfeld partitioning scheme is developed to analyze the time-dependent spin magnetization. In this work, we also introduce the coupling between electron spin and a homogenous magnetic field into the TDN2C framework to simulate the response of the electronic spin degrees of freedom to an external magnetic field. This is illustrated for several model systems, including the spin-frustrated Li{sub 3} molecule. Exact agreement is found between numerical and analytic results for Larmor precession of hydrogen and lithium atoms. The TDN2C method paves the way for the ab initio description of molecular spin transport and spintronics in the time domain.
Ab initio non-relativistic spin dynamics
NASA Astrophysics Data System (ADS)
Ding, Feizhi; Goings, Joshua J.; Frisch, Michael J.; Li, Xiaosong
2014-12-01
Many magnetic materials do not conform to the (anti-)ferromagnetic paradigm where all electronic spins are aligned to a global magnetization axis. Unfortunately, most electronic structure methods cannot describe such materials with noncollinear electron spin on account of formally requiring spin alignment. To overcome this limitation, it is necessary to generalize electronic structure methods and allow each electron spin to rotate freely. Here, we report the development of an ab initio time-dependent non-relativistic two-component spinor (TDN2C), which is a generalization of the time-dependent Hartree-Fock equations. Propagating the TDN2C equations in the time domain allows for the first-principles description of spin dynamics. A numerical tool based on the Hirshfeld partitioning scheme is developed to analyze the time-dependent spin magnetization. In this work, we also introduce the coupling between electron spin and a homogenous magnetic field into the TDN2C framework to simulate the response of the electronic spin degrees of freedom to an external magnetic field. This is illustrated for several model systems, including the spin-frustrated Li3 molecule. Exact agreement is found between numerical and analytic results for Larmor precession of hydrogen and lithium atoms. The TDN2C method paves the way for the ab initio description of molecular spin transport and spintronics in the time domain.
NASA Astrophysics Data System (ADS)
Lal, Sohan; Pandey, Sudhir K.
2016-08-01
In the present work, we investigate the applicability of the LSDA+U method in understanding the electronic and magnetic properties of a geometrically frustrated ZnV2O4 compound, where the delicate balance of electrons, lattice, orbital and spin interactions play an important role in deciding its physical properties. In the ferromagnetic solution of the compound, only one type of orbital solution is found to exist in all ranges of U studied here. However, in antiferromagnetic (AFM) phase, two types of orbital solutions, AFM(OS1) and AFM(OS2), exist for U > 3 eV. If the difference of the electronic occupancy of dxz and dyz orbitals is less than 0.25, then AFM(OS1) solution is stabilized, whereas for higher values AFM(OS2) solution is stabilized. The use of unconstrained calculations within the fully localized double counting scheme is unable to predict the AFM ground state for U ≤ 3 eV. Our results clearly suggest the importance of constrained calculations in understanding the electronic and magnetic properties of a compound, where various competing interactions are present. In the AFM solution, the orbital ground state of the compound changes with varying U, where AFM(OS1) is found to be the ground state for U ≤ 3 eV and for higher values of U, AFM(OS2) is the ground state. The analysis of the band gap suggests that the AFM(OS2) is the real ground state of the compound.
NASA Astrophysics Data System (ADS)
Mikhailov, S. A.
2002-03-01
Energy spectra, electron densities, pair-correlation functions, and heat capacity of quantum-dot lithium in zero external magnetic field (a system of three interacting two-dimensional electrons in a parabolic confinement potential) are studied using the exact diagonalization approach. Particular attention is given to a Fermi liquid-Wigner solid crossover in the ground state of the dot, induced by intradot Coulomb interaction.
NASA Astrophysics Data System (ADS)
Hayashi, M.; Nakamura, Y.
1998-10-01
The electron drift velocity in carbon dioxide was calculated at gas temperatures ranging from 193 to 573 K and at E/N values up to 100 Td, assuming that the gas was a mixture of ground state and vibrationally excited molecules and that the mix-ratio was determined by the gas temperature. The elastic momentum cross sections for the ground and the vibrationally excited molecules used in the present calculation were based on the compilation of Hayashi (1990) and recent experiments of Nakamura (1995) and Strakeljahn (1998). We also assumed that all other inelastic cross sections for the ground and the vibrationally excited molecules were the same (Schulz 1969, Srivastava 1983). The calculated electron drift velocity showed marked temperature dependence which agreed fairly well with the measurement of Elford (1980).
Delgado, Juan C; Selsby, Ronald G
2013-01-01
The ground state configuration of the gas phase cationic dyes pinacyanol chloride and rhodamine B are optimized with HF/6-311 + G(2d,2p) method and basis set. B3PW91/6-311 + G(2df,2p) functional and basis set is used to calculate the Mulliken atom charge distribution, total molecular energy, the dipole moment, the vertical ionization potential, the adiabatic electron affinity and the lowest excited triplet state, the last three as an energy difference between separately calculated open shell and ground states. The triplet and extra electron states are optimized to find the relaxation energy. In the ground state optimization of both dyes the chloride anion migrates to a position near the center of the chromophore. For rhodamine B the benzoidal group turns perpendicular to the chromophore plane. For both dyes, the LUMO is mostly of π character associated with the aromatic part of the molecule containing the chromophore. The highest occupied MOs consist of three almost degenerate eigenvectors involving the chloride anion coordinated with σ electrons in the molecular framework. The fourth highest MO is of π character. For both molecules in the gas phase ionization process the chloride anion loses the significant fraction of electric charge. In electron capture, the excess charge goes mainly on the dye cation. PMID:22891949
Gurtubay, I G; Gaudoin, R; Pitarke, J M
2010-02-17
We report variational and diffusion quantum Monte Carlo ground-state energies of the three-dimensional electron gas using a model periodic Coulomb interaction and backflow corrections for N = 54, 102, 178, and 226 electrons. We remove finite-size effects by extrapolation and we find lower energies than previously reported. Using the Hellman-Feynman operator sampling method introduced in Gaudoin and Pitarke (2007 Phys. Rev. Lett. 99 126406), we compute accurately, within the fixed-node approximation, the separate kinetic and interaction contributions to the total ground-state energy. The difference between the interaction energies obtained from the original Slater-determinant nodes and the backflow-displaced nodes is found to be considerably larger than the difference between the corresponding kinetic energies. PMID:21389370
Yoon, Jungjoo; Solomon, Edward I.
2008-01-01
The ground state electronic and magnetic properties of one of the possible structures of the trinuclear CuII site in the native intermediate (NI) of the multicopper oxidases, the μ3-oxo bridged structure, are evaluated using the C3-symmetric Cu3II complex, μ3O. μ3O is unique in that no ligand, other than the oxo, contributes to the exchange coupling. However, μ3O has a ferromagnetic ground state, inconsistent with that of NI. Therefore, two perturbations have been considered: protonation of the μ3-oxo ligand and relaxation of the μ3-oxo ligand into the Cu3 plane. Notably, when the oxo-ligand is sufficiently close to the Cu3 plane (< 0.3 Å), the ground state of μ3O becomes antiferromagnetic and can be correlated to that of NI. In addition, the ferromagnetic 4A ground state of μ3O is found from variable-temperature EPR to undergo a zero-field splitting (ZFS) of 2D = -5.0 cm-1, which derives from the second-order anisotropic exchange. This allows evaluation of the σ-to-π excited state exchange pathways and provides experimental evidence that the orbitally-degenerate 2E ground state of the antiferromagnetic μ3O would also undergo a ZFS by the first-order antisymmetric exchange that has the same physical origin as the anisotropic exchange. The important contribution of the μ3-oxo bridge to the ground-to-ground and ground-to-excited state superexchange pathways that are responsible for the isotropic, antisymmetric and anisotropic exchange are discussed. PMID:16241158
Dai, Xing; Gao, Yang; Xin, Minsi; Wang, Zhigang; Zhou, Ruhong
2014-12-28
As a representative lanthanide endohedral metallofullerene, Gd@C{sub 82} has attracted a widespread attention among theorists and experimentalists ever since its first synthesis. Through comprehensive comparisons and discussions, as well as references to the latest high precision experiments, we evaluated the performance of different computational methods. Our results showed that the appropriate choice of the exchange-correlation functionals is the decisive factor to accurately predict both geometric and electronic structures for Gd@C{sub 82}. The electronic structure of the ground state and energy gap between the septet ground state and the nonet low-lying state obtained from pure density functional methods, such as PBE and PW91, are in good agreement with current experiment. Unlike pure functionals, the popularly used hybrid functionals in previous studies, such as B3LYP, could infer the qualitative correct ground state only when small basis set for C atoms is employed. Furthermore, we also highlighted that other geometric structures of Gd@C{sub 82} with the Gd staying at different positions are either not stable or with higher energies. This work should provide some useful references for various theoretical methodologies in further density functional studies on Gd@C{sub 82} and its derivatives in the future.
NASA Astrophysics Data System (ADS)
Kashima, Tsuyoshi; Imada, Masatoshi
2001-08-01
A new efficient numerical algorithm for interacting fermion systems is proposed and examined in detail. The ground state is expressed approximately by a linear combination of numerically chosen basis states in a truncated Hilbert space. Two procedures lead to a better approximation. The first is a numerical renormalization, which optimizes the chosen basis and projects onto the ground state within the fixed dimension, L, of the Hilbert space. The second is an increase of the dimension of the truncated Hilbert space, which enables the linear combination to converge to a better approximation. The extrapolation L→∞ after the convergence removes the approximation error systematically. This algorithm does not suffer from the negative sign problem and can be applied to systems in any spatial dimension and arbitrary lattice structure. The efficiency is tested and the implementation explained for two-dimensional Hubbard models where Slater determinants are employed as chosen basis. Our results with less than 400 chosen basis indicate good accuracy within the errorbar of the best available results as those of the quantum Monte Carlo for energy and other physical quantities.
NASA Astrophysics Data System (ADS)
Whitfield, James; Faccin, Mauro; Biamonte, Jacob
2013-03-01
Designing and optimizing cost functions and energy landscapes is a problem encountered in many fields of science and engineering. These landscapes and cost functions can be embedded and annealed in experimentally controllable spin Hamiltonians. Using an approach based on group theory and symmetries, we examine the embedding of Boolean logic gates into the ground-state subspace of such spin systems. We describe parameterized families of diagonal Hamiltonians and symmetry operations which preserve the ground-state subspace encoding the truth tables of Boolean formulas. The ground-state embeddings of adder circuits are used to illustrate how gates are combined and simplified using symmetry. Our work is relevant for experimental demonstrations of ground-state embeddings found in both classical optimization as well as adiabatic quantum optimization.
NASA Technical Reports Server (NTRS)
Arnold, J. O.; Nicholls, R. W.
1973-01-01
The CN ground state dissociation energy and the sum of squares of the electronic transition moments of the CN violet bands have been simultaneously determined from spectral emission measurements behind incident shock waves. The unshocked test gases were composed of various CO2-CO-N2-Ar mixtures, and the temperatures behind the incident shocks ranged from 3500 to 8000 K. The variation of the electronic transition moment with internuclear separation was found to be small for both the CN violet and red band systems.
Lefrancois, Daniel; Wormit, Michael; Dreuw, Andreas
2015-09-28
For the investigation of molecular systems with electronic ground states exhibiting multi-reference character, a spin-flip (SF) version of the algebraic diagrammatic construction (ADC) scheme for the polarization propagator up to third order perturbation theory (SF-ADC(3)) is derived via the intermediate state representation and implemented into our existing ADC computer program adcman. The accuracy of these new SF-ADC(n) approaches is tested on typical situations, in which the ground state acquires multi-reference character, like bond breaking of H{sub 2} and HF, the torsional motion of ethylene, and the excited states of rectangular and square-planar cyclobutadiene. Overall, the results of SF-ADC(n) reveal an accurate description of these systems in comparison with standard multi-reference methods. Thus, the spin-flip versions of ADC are easy-to-use methods for the calculation of “few-reference” systems, which possess a stable single-reference triplet ground state.
Entropy current for non-relativistic fluid
NASA Astrophysics Data System (ADS)
Banerjee, Nabamita; Dutta, Suvankar; Jain, Akash; Roychowdhury, Dibakar
2014-08-01
We study transport properties of a parity-odd, non-relativistic charged fluid in presence of background electric and magnetic fields. To obtain stress tensor and charged current for the non-relativistic system we start with the most generic relativistic fluid, living in one higher dimension and reduce the constituent equations along the light-cone direction. We also reduce the equation satisfied by the entropy current of the relativistic theory and obtain a consistent entropy current for the non-relativistic system (we call it "canonical form" of the entropy current). Demanding that the non-relativistic fluid satisfies the second law of thermodynamics we impose constraints on various first order transport coefficients. For parity even fluid, this is straight forward; it tells us positive definiteness of different transport coefficients like viscosity, thermal conductivity, electric conductivity etc. However for parity-odd fluid, canonical form of the entropy current fails to confirm the second law of thermodynamics. Therefore, we need to add two parity-odd vectors to the entropy current with arbitrary coefficients. Upon demanding the validity of second law, we see that one can fix these two coefficients exactly.
NASA Astrophysics Data System (ADS)
Neira Bueno, O. L.; Hincapié H, L.; García Madrid, C.
2016-02-01
The study of geometric, electronic properties and intrinsic chemical reactivity is presented for the case of Quinoline and three-derived molecules (4-Amino-Quinoline, 3- Phenyl-Quinoline, 4-Amino-3-phenylquinoline). The study was carried for the ground state in gas phase in the context of the functional theory density using B3LYP/6 31+G (d) model. The purpose of the study is aimed for identifying a compound derived from quinoline, on based to mono- or bi-substitution, using the amino fragment and the phenyl group.
Electron-Capture Cross Sections of Ground-State O2+ Recoil Ions in Slow Collisions with H2 and O2
Hasan, Asad T.; Gray, Tom J.
2007-01-01
We report the measured total charge-transfer (electron-capture) cross sections for the ground state O2+ (X2Πg) ions with H2 and O2 molecular gases in the collision energy range between 0.50 and 2 keV. The time-of-flight technique has been used to measure the fast neutral products from O2+ charge transfer reactions. The analyzed process has cross sections that continue to increase slowly, as a function of incident energy. Measured cross sections for O2++H2, O2 systems are compared with previously available experimental and theoretical results in the literature.
Koga, T.; Yamamoto, Y. ); Kryachko, E.S.
1989-10-15
The recently proposed method of density mapping between momentum and position spaces is applied to the ground state of the helium atom. The Kellner densities and wave functions are used as reference, and the Eckart densities {gamma}({bold p}) and {rho}({bold r}) are employed as test densities keeping their parent wave functions in blind. From the momentum density {gamma}({bold p}), the corresponding position density {rho}{sub {gamma}}({bold r}) and the position moments {l angle}{ital r}{sup {ital n}}{r angle}{sub {gamma}} ({minus}2{le}{ital n}{le}4) are generated within a few percent error. The inverse procedure generates the momentum density {gamma}{sub {rho}}({bold p}) and the momentum moments {l angle}{ital p}{sup {ital n}}{r angle}{sub {rho}} ({minus}2{le}{ital n}{le}4) from the position density {rho}({bold r}) with a better accuracy. Density-functional calculations are performed in a simplified manner and the energies close to the Hartree--Fock limit value are obtained.
NASA Astrophysics Data System (ADS)
Suzuki, M.-T.; Magnani, N.; Oppeneer, P. M.
2013-11-01
The electronic states of the actinide dioxides AnO2 (with An = U, Np, Pu, Am, and Cm) are investigated employing first-principles calculations within the framework of the local density approximation +U (LDA+U) approach, implemented in a full-potential linearized augmented plane-wave scheme. A systematic analysis of the An-5f states is performed which provides intuitive connections between the electronic structures and the local crystalline fields of the f states in the AnO2 series. Particularly the mechanisms leading to the experimentally observed insulating ground states are investigated. These are found to be caused by the strong spin-orbit and Coulomb interactions of the 5f orbitals; however, as a result of the different configurations, this mechanism works in distinctly different ways for each of the AnO2 compounds. In agreement with experimental observations, the nonmagnetic states of plutonium and curium dioxide are computed to be insulating, whereas those of uranium, neptunium, and americium dioxides require additional symmetry breaking to reproduce the insulator ground states, a condition which is met with magnetic phase transitions. We show that the occupancy of the An-f orbitals is closely connected to each of the appearing insulating mechanisms. We furthermore investigate the detailed constitution of the noncollinear multipolar moments for transverse 3q magnetic ordered states in UO2 and longitudinal 3q high-rank multipolar ordered states in NpO2 and AmO2.
Local supersymmetry in non-relativistic systems
NASA Astrophysics Data System (ADS)
Urrutia, L. F.; Zanelli, J.
1989-10-01
Classical and quantum non-relativistic interacting systems invariant under local supersymmetry are constructed by the method of taking square roots of the bosonic constraints which generate timelike reparameterization, leaving the action unchanged. In particular, the square root of the Schroedinger constraint is shown to be the non-relativistic limit of the Dirac constraint. Contact is made with the standard models of Supersymmetric Quantum Mechanics through the reformulation of the locally invariant systems in terms of their true degrees of freedom. Contrary to the field theory case, it is shown that the locally invariant systems are completely equivalent to the corresponding globally invariant ones, the latter being the Heisenberg picture description of the former, with respect to some fermionic time.
Renormalization group for non-relativistic fermions.
Shankar, R
2011-07-13
A brief introduction is given to the renormalization group for non-relativistic fermions at finite density. It is shown that Landau's theory of the Fermi liquid arises as a fixed point (with the Landau parameters as marginal couplings) and its instabilities as relevant perturbations. Applications to related areas, nuclear matter, quark matter and quantum dots, are briefly discussed. The focus will be on explaining the main ideas to people in related fields, rather than addressing the experts. PMID:21646269
NASA Astrophysics Data System (ADS)
Appel, Markus; Frick, Bernhard; Elbert, Johannes; Gallei, Markus; Stühn, Bernd
2015-01-01
The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene). They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.
NASA Astrophysics Data System (ADS)
Bisogni, Valentina; Catalano, Sara; Green, Robert; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Balandesh, Shadi; Strocov, Vladimir N.; Zubko, Pavlo; Sawatzky, George; Triscone, Jean-Marc; Schmitt, Thorsten
Rare-earth nickelates ReNiO3 attract a lot of interest thanks to their intriguing physical properties like sharp metal to insulator transition, unusual magnetic order and expected superconductivity in nickelate-based heterostructures. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). Taking a NdNiO3 thin film as a representative example, we reveal with x-ray absorption and resonant inelastic x-ray scattering unusual coexistence of bound and continuum excitations, providing strong evidence for abundant O 2p holes in the GS of these materials. Using an Anderson impurity model interpretation, we show that these distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the O 2p valence band, confirming suggestions that these materials exhibit a negative charge-transfer energy, with O 2p states extending across the Fermi level.
Characterizing the electronic ground states of single-layer NbSe2 via STM/STS
NASA Astrophysics Data System (ADS)
Chen, Yi; Ugeda, Miguel; Bradley, Aaron; Zhang, Yi; Onishi, Seita; Ruan, Wei; Ojeda-Aristizabal, Claudia; Ryu, Hyejin; Edmonds, Mark; Tsai, Hsin-Zon; Riss, Alexander; Mo, Sung-Kwan; Lee, Dunghai; Zettl, Alex; Hussain, Zahid; Shen, Zhi-Xun; Crommie, Michael
Layered transition metal dichalcogenides (TMDs) are ideal systems for exploring collective electronic phases such as charge density wave (CDW) order and superconductivity. In bulk NbSe2 the CDW sets in at TCDW = 33K and superconductivity sets in at Tc = 7.2K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single 2D layer of NbSe2 by means of low temperature scanning tunneling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and electrical transport measurements. We demonstrate that the CDW order remains intact in 2D and exhibits a robust 3 x 3 superlattice. Superconductivity also still occurs but its onset is depressed to 1.6K. Our STS measurements at 5K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible via STS due to the removal of bands crossing the Fermi surface in the 2D limit. Our observations are consistent with the predicted simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing new insight into CDW formation and superconductivity in this model strongly-correlated system.
On the ground state of metallic hydrogen
NASA Technical Reports Server (NTRS)
Chakravarty, S.; Ashcroft, N. W.
1978-01-01
A proposed liquid ground state of metallic hydrogen at zero temperature is explored and a variational upper bound to the ground state energy is calculated. The possibility that the metallic hydrogen is a liquid around the metastable point (rs = 1.64) cannot be ruled out. This conclusion crucially hinges on the contribution to the energy arising from the third order in the electron-proton interaction which is shown here to be more significant in the liquid phase than in crystals.
Marquardt, Roberto; Sagui, Kenneth; Zheng, Jingjing; Thiel, Walter; Luckhaus, David; Yurchenko, Sergey; Mariotti, Fabio; Quack, Martin
2013-08-15
The analytical, full-dimensional, and global representation of the potential energy surface of NH(3) in the lowest adiabatic electronic state developed previously (Marquardt, R.; et al. J. Phys. Chem. B 2005, 109, 8439–8451) is improved by adjustment of parameters to an enlarged set of electronic energies from ab initio calculations using the coupled cluster method with single and double substitutions and a perturbative treatment of connected triple excitations (CCSD(T)) and the method of multireference configuration interaction (MRCI). CCSD(T) data were obtained from an extrapolation of aug-cc-pVXZ results to the basis set limit (CBS), as described in a previous work (Yurchenko, S.N.; et al. J. Chem. Phys 2005, 123, 134308); they cover the region around the NH3 equilibrium structures up to 20,000 hc cm(–1). MRCI energies were computed using the aug-cc-pVQZ basis to describe both low lying singlet dissociation channels. Adjustment was performed simultaneously to energies obtained from the different ab initio methods using a merging strategy that includes 10,000 geometries at the CCSD(T) level and 500 geometries at the MRCI level. Characteristic features of this improved representation are NH3 equilibrium geometry r(eq)(NH(3)) ≈ 101.28 pm, α(eq)(NH(3)) ≈ 107.03°, the inversion barrier at r(inv)(NH(3)) ≈ 99.88 pm and 1774 hc cm(–1) above the NH(3) minimum, and dissociation channel energies 41,051 hc cm(–1) (for NH(3) → ((2)B(2))NH(2) + ((2)S(1/2))H) and 38,450 hc cm(–1) (for NH(3) → ((3)Σ(–))NH +((1)Σ(g)(+))H(2)); the average agreement between calculated and experimental vibrational line positions is 11 cm(–1) for (14)N(1)H(3) in the spectral region up to 5000 cm(–1). A survey of our current knowledge on the vibrational spectroscopy of ammonia and its isotopomers is also given. PMID:23688044
Non-relativistic fields from arbitrary contracting backgrounds
NASA Astrophysics Data System (ADS)
Bergshoeff, Eric; Rosseel, Jan; Zojer, Thomas
2016-09-01
We discuss a non-relativistic contraction of massive and massless field theories minimally coupled to gravity. Using the non-relativistic limiting procedure introduced in our previous work, we (re-)derive non-relativistic field theories of massive and massless spins 0 to 3/2 coupled to torsionless Newton–Cartan backgrounds. We elucidate the relativistic origin of the Newton–Cartan central charge gauge field {m}μ and explain its relation to particle number conservation.
NASA Astrophysics Data System (ADS)
Kristyan, Sandor
2013-11-01
Using orbital-free framework, a simple numerical optimization of the density functional for ground state electronic energy is described for any type of functional approximation, demonstrated via the example of linear combinations of homogeneous functionals of the density. The numerical recipe is given and analyzed for solution: Originating from the linear dependence of nuclear-electron attraction functional on one-electron density ( V ne[ ρ 0( r 1)] = -ΣA = 1,…,MZA∫ ρ 0( r 1)rA1 -1d r 1), and a quadratic LCAO approximation for ρ 0, the optimization can be done with iterative use of lin-solver. This quadratic approximation, as simplest educated choice for ρ 0, is compared and analyzed algebraically to the HF-SCF one in the Appendices. We call the attention that the introduction of a self-consistent field optimization of non-linear density functional is a new element in this part of the related, general theory.
Cho, Daeheum; Ko, Kyoung Chul; Lamiel-García, Oriol; Bromley, Stefan T; Lee, Jin Yong; Illas, Francesc
2016-08-01
We investigated the influence of size and structure on the electronic structure of TiO2 nanoparticles 0.5-3.2 nm in diameter, in both vacuum and water, using density functional theory (DFT) calculations. Specifically, we tracked the optical and electronic energy gap of a set of (TiO2)n nanoparticles ranging from small non-bulklike clusters with n = 4, 8, and 16, to larger nanoparticles derived from the anatase bulk crystal with n = 35 and 84. As the difference between these two energy gaps (the exciton binding energy) becomes negligible in the bulk, this magnitude provides an indicator of the bulklike character of the electronic structure of the nanoparticles under study. Extrapolating our results to larger sizes, we obtain a rough estimate of the nanoparticle size at which the electronic structure will begin to be effectively bulklike. Our results generally confirmed that the electronic structure of the nanoparticle ground state and excited state has a more pronounced structure dependency than size dependency within a size range of 0.5-1.5 nm. We also showed that the thermodynamic preference for the photocatalytic species is the first S1 exciton. This S1 exciton is stable under vacuum but may evolve to free charge carriers upon structural relaxation in an aqueous environment for particles 0.5-1.5 nm in size studied in the present article. An analysis of ionization potentials and electron affinities, relative to the standard reduction potential for the water splitting half-reactions, revealed the importance of considering the structural relaxation in the excited states and the presence of water for assessing the thermodynamic conditions for photocatalytic water splitting. PMID:27379415
Microscopic picture of non-relativistic classicalons
Berkhahn, Felix; Müller, Sophia; Niedermann, Florian; Schneider, Robert E-mail: sophia.x.mueller@physik.uni-muenchen.de E-mail: robert.bob.schneider@physik.uni-muenchen.de
2013-08-01
A theory of a non-relativistic, complex scalar field with derivatively coupled interaction terms is investigated. This toy model is considered as a prototype of a classicalizing theory and in particular of general relativity, for which the black hole constitutes a prominent example of a classicalon. Accordingly, the theory allows for a non-trivial solution of the stationary Gross-Pitaevskii equation corresponding to a black hole in the case of GR. Quantum fluctuations on this classical background are investigated within the Bogoliubov approximation. It turns out that the perturbative approach is invalidated by a high occupation of the Bogoliubov modes. Recently, it was proposed that a black hole is a Bose-Einstein condensate of gravitons that dynamically ensures to stay at the verge of a quantum phase transition. Our result is understood as an indication for that claim. Furthermore, it motivates a non-linear numerical analysis of the model.
Ionization energies and term energies of the ground states 1s22s of lithium-like systems
NASA Astrophysics Data System (ADS)
Li, Jin-Ying; Wang, Zhi-Wen
2014-01-01
We extend the Hamiltonian method of the full-core plus correlation (FCPC) by minimizing the expectation value to calculate the non-relativistic energies and the wave functions of 1s22s states for the lithium-like systems from Z = 41 to 50. The mass-polarization and the relativistic corrections including the kinetic-energy correction, the Darwin term, the electron—electron contact term, and the orbit—orbit interaction are calculated perturbatively as first-order correction. The contribution from quantum electrodynamic (QED) is also explored by using the effective nuclear charge formula. The ionization potential and term energies of the ground states 1s22s are derived and compared with other theoretical calculation results. It is shown that the FCPC methods are also effective for theoretical calculation of the ionic structure for high nuclear ion of lithium-like systems.
The Thomas–Fermi quark model: Non-relativistic aspects
Liu, Quan Wilcox, Walter
2014-02-15
The first numerical investigation of non-relativistic aspects of the Thomas–Fermi (TF) statistical multi-quark model is given. We begin with a review of the traditional TF model without an explicit spin interaction and find that the spin splittings are too small in this approach. An explicit spin interaction is then introduced which entails the definition of a generalized spin “flavor”. We investigate baryonic states in this approach which can be described with two inequivalent wave functions; such states can however apply to multiple degenerate flavors. We find that the model requires a spatial separation of quark flavors, even if completely degenerate. Although the TF model is designed to investigate the possibility of many-quark states, we find surprisingly that it may be used to fit the low energy spectrum of almost all ground state octet and decuplet baryons. The charge radii of such states are determined and compared with lattice calculations and other models. The low energy fit obtained allows us to extrapolate to the six-quark doubly strange H-dibaryon state, flavor symmetric strange states of higher quark content and possible six quark nucleon–nucleon resonances. The emphasis here is on the systematics revealed in this approach. We view our model as a versatile and convenient tool for quickly assessing the characteristics of new, possibly bound, particle states of higher quark number content. -- Highlights: • First application of the statistical Thomas–Fermi quark model to baryonic systems. • Novel aspects: spin as generalized flavor; spatial separation of quark flavor phases. • The model is statistical, but the low energy baryonic spectrum is successfully fit. • Numerical applications include the H-dibaryon, strange states and nucleon resonances. • The statistical point of view does not encourage the idea of bound many-quark baryons.
Woertink, Julia S.; Tian, Li; Maiti, Debabrata; Lucas, Heather R.; Himes, Richard A.; Karlin, Kenneth D.; Neese, Frank; Würtele, Christian; Holthausen, Max; Bill, Eckhard; Sundermeyer, Jörg; Schindler, Siegfried; Solomon, Edward I.
2010-01-01
A variety of techniques including absorption, magnetic circular dichroism (MCD), variable-temperature, variable-field MCD (VTVH-MCD), and resonance Raman (rR) spectroscopies are combined with density function theory (DFT) calculations to elucidate the electronic structure of the end-on (η1) bound superoxo-Cu(II) complex [TMG3trenCuO2]+ (where TMG3tren is 1,1,1-tris[2-[N2-(1,1,3,3- tetramethylguanidino)]ethyl]amine). The spectral features of [TMG3trenCuO2]+ are assigned, including the first definitive assignment of a superoxo intraligand transition in a metal-superoxo complex, and a detailed description of end-on superoxo-Cu(II) bonding is developed. The lack of overlap between the two magnetic orbitals of [TMG3trenCuO2]+ eliminates antiferromagnetic coupling between the copper(II) and the superoxide, while the significant superoxo π*σ character of the copper dz2 orbital leads to its ferromagneticly coupled, triplet, ground state. PMID:20857998
NASA Astrophysics Data System (ADS)
Abdel-Rahim, G. P.; Rodríguez M, J. A.; Moreno-Armenta, M. G.
2013-11-01
We study the structural and electronic properties of YC in volume using density functional theory (DFT) within the generalized gradient approximation (GGA), using the scheme of Wu-Cohen 2006 and Tran et al. 2007. Several crystal structures were considered: Nickel Arsenide (NiAs), Sodium Chloride (NaCl), Cesium Chloride (CsCl), and zincblende (ZB). A new fact that we present in this paper is the inclusion of the NiAs-like structure, which is the true ground state (GS) for YC. We calculated the density of states (DOS) and the band structure and found that YC is non-magnetic and its behavior is metallic-like. The lattice parameter alatt is 3.69 Å and the c/a = 1.47. Cohesion energy (Ecoh) is -12.90 eV, which is very close to Ecoh of the NaCl structure. Therefore, YC exists in these two structures. Our results with respect to alatt, bulk modulus (B), Ecoh, and the main features of the electronic properties are in good agreement with those found by other researchers. Other researchers found a transition from NaCl to CsCl, but we found a new transition from NiAs to CsCl, where the volume diminishes ~10% and its transition pressure (PT ~79 GPa) is very close to the 80 GPa of the former. The contraction can fracture the material if it is worked on near the transition. For pressures before and after the transition, YC maintains non-magnetic and metallic behaviors.
Accuracy of the non-relativistic approximation for momentum diffusion
NASA Astrophysics Data System (ADS)
Liang, Shiuan-Ni; Lan, Boon Leong
2016-06-01
The accuracy of the non-relativistic approximation, which is calculated using the same parameter and the same initial ensemble of trajectories, to relativistic momentum diffusion at low speed is studied numerically for a prototypical nonlinear Hamiltonian system -the periodically delta-kicked particle. We find that if the initial ensemble is a non-localized semi-uniform ensemble, the non-relativistic approximation to the relativistic mean square momentum displacement is always accurate. However, if the initial ensemble is a localized Gaussian, the non-relativistic approximation may not always be accurate and the approximation can break down rapidly.
Serra, Pablo
2006-07-15
In a recent paper [Phys. Rev. A 71, 042501 (2005)], Howard and March presented the exact ground state wave function of the spherical He-like atom, and many physical aspects of this solution were analyzed. We show that this function is not the exact solution of the model.
Ground state energy of large polaron systems
Benguria, Rafael D.; Frank, Rupert L.; Lieb, Elliott H.
2015-02-15
The last unsolved problem about the many-polaron system, in the Pekar–Tomasevich approximation, is the case of bosons with the electron-electron Coulomb repulsion of strength exactly 1 (the “neutral case”). We prove that the ground state energy, for large N, goes exactly as −N{sup 7/5}, and we give upper and lower bounds on the asymptotic coefficient that agree to within a factor of 2{sup 2/5}.
NASA Astrophysics Data System (ADS)
Whitfield, J. D.; Faccin, M.; Biamonte, J. D.
2012-09-01
Designing and optimizing cost functions and energy landscapes is a problem encountered in many fields of science and engineering. These landscapes and cost functions can be embedded and annealed in experimentally controllable spin Hamiltonians. Using an approach based on group theory and symmetries, we examine the embedding of Boolean logic gates into the ground-state subspace of such spin systems. We describe parameterized families of diagonal Hamiltonians and symmetry operations which preserve the ground-state subspace encoding the truth tables of Boolean formulas. The ground-state embeddings of adder circuits are used to illustrate how gates are combined and simplified using symmetry. Our work is relevant for experimental demonstrations of ground-state embeddings found in both classical optimization as well as adiabatic quantum optimization.
Aucar, I Agustín; Gómez, Sergio S; Melo, Juan I; Giribet, Claudia C; Ruiz de Azúa, Martín C
2013-04-01
In the present work, numerical results of the nuclear spin-rotation (SR) tensor in the series of compounds HX (X = H,F,Cl,Br,I) within relativistic 4-component expressions obtained by Aucar et al. [J. Chem. Phys. 136, 204119 (2012)] are presented. The SR tensors of both the H and X nuclei are discussed. Calculations were carried out within the relativistic Linear Response formalism at the Random Phase Approximation with the DIRAC program. For the halogen nucleus X, correlation effects on the non-relativistic values are shown to be of similar magnitude and opposite sign to relativistic effects. For the light H nucleus, by means of the linear response within the elimination of the small component approach it is shown that the whole relativistic effect is given by the spin-orbit operator combined with the Fermi contact operator. Comparison of "best estimate" calculated values with experimental results yield differences smaller than 2%-3% in all cases. The validity of "Flygare's relation" linking the SR tensor and the NMR nuclear magnetic shielding tensor in the present series of compounds is analyzed. PMID:23574208
NASA Astrophysics Data System (ADS)
Aucar, I. Agustín; Gómez, Sergio S.; Melo, Juan I.; Giribet, Claudia C.; Ruiz de Azúa, Martín C.
2013-04-01
In the present work, numerical results of the nuclear spin-rotation (SR) tensor in the series of compounds HX (X=H,F,Cl,Br,I) within relativistic 4-component expressions obtained by Aucar et al. [J. Chem. Phys. 136, 204119 (2012), 10.1063/1.4721627] are presented. The SR tensors of both the H and X nuclei are discussed. Calculations were carried out within the relativistic Linear Response formalism at the Random Phase Approximation with the DIRAC program. For the halogen nucleus X, correlation effects on the non-relativistic values are shown to be of similar magnitude and opposite sign to relativistic effects. For the light H nucleus, by means of the linear response within the elimination of the small component approach it is shown that the whole relativistic effect is given by the spin-orbit operator combined with the Fermi contact operator. Comparison of "best estimate" calculated values with experimental results yield differences smaller than 2%-3% in all cases. The validity of "Flygare's relation" linking the SR tensor and the NMR nuclear magnetic shielding tensor in the present series of compounds is analyzed.
Ground state of the hydrogen negative ion
NASA Astrophysics Data System (ADS)
Obreshkov, Boyan
2009-03-01
Based on recently developed variational many-body Schr"odinger equation for electrons with Coulomb interactions [1], we provide first numerical results for the ground state electron structure of the hydrogen negative ion. It is shown that Fermi-Teller promotion effect together with non-adiabatic screening effects due to the Pauli's exclusion principle are responsible for the weak binding of the anion. The calculated ionization potential J=-1/2 - 2 λ+ <1/r12> of the hydrogen negative ion is compared with the experiment, where λ is the mean binding energy per one electron in the ground state.[0pt] [1] B. D. Obreshkov , Phys. Rev. A 78, 032503 (2008).
Influence of electron doping on the ground state of (Sr_{1-x}La_{x})_{2}IrO_{4}
Chen, Xiang; Hogan, Tom; Walkup, D.; Zhou, Wenwen; Pokharel, M.; Yao, Mengliang; Tian, Wei; Ward, Thomas Zac; Zhao, Y.; Parshall, Dr. D.; Opeil, C.; Lynn, J. W.; Madhavan, Vidya; Wilson, Stephen
2015-08-17
The evolution of the electronic properties of electron-doped (Sr_{1-x}La_{x})_{2}IrO_{4} is experimentally explored as the doping limit of La is approached. As electrons are introduced, the electronic ground state transitions from a spin-orbit Mott phase into an electronically phase separated state, where long-range magnetic order vanishes beyond x = 0:02 and charge transport remains percolative up to the limit of La substitution (x =0:06). In particular, the electronic ground state remains inhomogeneous even beyond the collapse of the parent state's long-range antiferromagnetic order, while persistent short-range magnetism survives up to the highest La-substitution levels. Furthermore, as electrons are doped into Sr_{2}IrO_{4}, we observe the appearance of a low temperature magnetic glass-like state intermediate to the complete suppression of antiferromagnetic order. Universalities and di erences in the electron-doped phase diagrams of single layer and bilayer Ruddlesden-Popper strontium iridates are discussed.
Ground states of holographic superconductors
Gubser, Steven S.; Nellore, Abhinav
2009-11-15
We investigate the ground states of the Abelian Higgs model in AdS{sub 4} with various choices of parameters, and with no deformations in the ultraviolet other than a chemical potential for the electric charge under the Abelian gauge field. For W-shaped potentials with symmetry-breaking minima, an analysis of infrared asymptotics suggests that the ground state has emergent conformal symmetry in the infrared when the charge of the complex scalar is large enough. But when this charge is too small, the likeliest ground state has Lifshitz-like scaling in the infrared. For positive mass quadratic potentials, Lifshitz-like scaling is the only possible infrared behavior for constant nonzero values of the scalar. The approach to Lifshitz-like scaling is shown in many cases to be oscillatory.
Kaizaki, Sumio; Shirotani, Dai; Sato, Hisako
2013-06-28
For Δ-SAPR-8-Cs[Ln((+)-hfbc)4]((+)-hfbc = (+)-heptafluoro-butyrylcamphorate; Cs-Ln), the vibrational circular dichroism pattern and intensity of Cs-La, Cs-Nd, Cs-Gd, Cs-Ho, Cs-Er, Cs-Lu and Cs-Sm, Cs-Eu, Cs-Tb, Cs-Dy, Cs-Tm, Cs-Yb, respectively, are correlated with the even and the odd parity of total orbital angular momentum in the ground state terms. PMID:23689479
Ground-state properties of the periodic Anderson model
NASA Technical Reports Server (NTRS)
Blankenbecler, R.; Fulco, J. R.; Gill, W.; Scalapino, D. J.
1987-01-01
The ground-state energy, hybridization matrix element, local moment, and spin-density correlations of a one-dimensional, finite-chain, periodic, symmetric Anderson model are obtained by numerical simulations and compared with perturbation theory and strong-coupling results. It is found that the local f-electron spins are compensated by correlation with other f-electrons as well as band electrons leading to a nonmagnetic ground state.
Compton Effect with Non-Relativistic Kinematics
ERIC Educational Resources Information Center
Shivalingaswamy, T.; Kagali, B. A.
2011-01-01
In deducing the change of wavelength of x-rays scattered by atomic electrons, one normally makes use of relativistic kinematics for electrons. However, recoiling energies of the electrons are of the order of a few keV which is less than 0.2% of their rest energies. Hence the authors may ask whether relativistic formulae are really necessary. In…
Holographic forced fluid dynamics in non-relativistic limit
NASA Astrophysics Data System (ADS)
Cai, Rong-Gen; Li, Li; Nie, Zhang-Yu; Zhang, Yun-Long
2012-11-01
We study the thermodynamics and non-relativistic hydrodynamics of the holographic fluid on a finite cutoff surface in the Gauss-Bonnet gravity. It is shown that the isentropic flow of the fluid is equivalent to a radial component of gravitational field equations. We use the non-relativistic fluid expansion method to study the Einstein-Maxwell-dilaton system with a negative cosmological constant, and obtain the holographic incompressible forced Navier-Stokes equations of the dual fluid at AdS boundary and at a finite cutoff surface, respectively. The concrete forms of external forces are given.
Unstable particles in non-relativistic quantum mechanics?
Hernandez-Coronado, H.
2011-10-14
The Schroedinger equation is up-to-a-phase invariant under the Galilei group. This phase leads to the Bargmann's superselection rule, which forbids the existence of the superposition of states with different mass and implies that unstable particles cannot be described consistently in non-relativistic quantum mechanics (NRQM). In this paper we claim that Bargmann's rule neglects physical effects and that a proper description of non-relativistic quantum mechanics requires to take into account this phase through the Extended Galilei group and the definition of its action on spacetime coordinates.
Intense non-relativistic cesium ion beam
Lampel, M.C.
1984-02-01
The Heavy Ion Fusion group at Lawrence Berkeley Laboratory has constructed the One Ampere Cesium Injector as a proof of principle source to supply an induction linac with a high charge density and high brightness ion beam. This is studied here. An electron beam probe was developed as the major diagnostic tool for characterizing ion beam space charge. Electron beam probe data inversion is accomplished with the EBEAM code and a parametrically adjusted model radial charge distribution. The longitudinal charge distribution was not derived, although it is possible to do so. The radial charge distribution that is derived reveals an unexpected halo of trapped electrons surrounding the ion beam. A charge fluid theory of the effect of finite electron temperature on the focusing of neutralized ion beams (Nucl. Fus. 21, 529 (1981)) is applied to the problem of the Cesium beam final focus at the end of the injector. It is shown that the theory's predictions and assumptions are consistent with the experimental data, and that it accounts for the observed ion beam radius of approx. 5 cm, and the electron halo, including the determination of an electron Debye length of approx. 10 cm.
Relativistic and non-relativistic solitons in plasmas
NASA Astrophysics Data System (ADS)
Barman, Satyendra Nath
This thesis entitled as "Relativistic and Non-relativistic Solitons in Plasmas" is the embodiment of a number of investigations related to the formation of ion-acoustic solitary waves in plasmas under various physical situations. The whole work of the thesis is devoted to the studies of solitary waves in cold and warm collisionless magnetized or unmagnetized plasmas with or without relativistic effect. To analyze the formation of solitary waves in all our models of plasmas, we have employed two established methods namely - reductive perturbation method to deduce the Korteweg-de Vries (KdV) equation, the solutions of which represent the important but near exact characteristic concepts of soliton-physics. Next, the pseudopotential method to deduce the energy integral with total nonlinearity in the coupling process for exact characteristic results of solitons has been incorporated. In Chapter 1, a brief description of plasma in nature and laboratory and its generation are outlined elegantly. The nonlinear differential equations to characterize solitary waves and the relevant but important methods of solutions have been mentioned in this chapter. The formation of solitary waves in unmagnetized and magnetized plasmas, and in relativistic plasmas has been described through mathematical entity. Applications of plasmas in different fields are also put forwarded briefly showing its importance. The study of plasmas as they naturally occur in the universe encompasses number of topics including sun's corona, solar wind, planetary magnetospheres, ionospheres, auroras, cosmic rays and radiation. The study of space weather to understand the universe, communications and the activities of weather satellites are some useful areas of space plasma physics. The surface cleaning, sterilization of food and medical appliances, killing of bacteria on various surfaces, destroying of viruses, fungi, spores and plasma coating in industrial instruments ( like computers) are some of the fields
Non-Relativistic Twistor Theory and Newton-Cartan Geometry
NASA Astrophysics Data System (ADS)
Dunajski, Maciej; Gundry, James
2016-03-01
We develop a non-relativistic twistor theory, in which Newton-Cartan structures of Newtonian gravity correspond to complex three-manifolds with a four-parameter family of rational curves with normal bundle O oplus O(2)}. We show that the Newton-Cartan space-times are unstable under the general Kodaira deformation of the twistor complex structure. The Newton-Cartan connections can nevertheless be reconstructed from Merkulov's generalisation of the Kodaira map augmented by a choice of a holomorphic line bundle over the twistor space trivial on twistor lines. The Coriolis force may be incorporated by holomorphic vector bundles, which in general are non-trivial on twistor lines. The resulting geometries agree with non-relativistic limits of anti-self-dual gravitational instantons.
Cyclotron resonance in topological insulators: non-relativistic effects
NASA Astrophysics Data System (ADS)
Tabert, C. J.; Carbotte, J. P.
2015-09-01
The low-energy Hamiltonian used to describe the dynamics of the helical Dirac fermions on the surface of a topological insulator contains a subdominant non-relativistic (Schrödinger) contribution. This term can have an important effect on some properties while having no effect on others. The Hall plateaus retain the same relativistic quantization as the pure Dirac case. The height of the universal interband background conductivity is unaltered, but its onset is changed. However, the non-relativistic term leads directly to particle-hole asymmetry. It also splits the interband magneto-optical lines into doublets. Here, we find that, while the shape of the semiclassical cyclotron resonance line is unaltered, the cyclotron frequency and its optical spectral weight are changed. There are significant differences in both of these quantities for a fixed value of chemical potential or fixed doping away from charge neutrality depending on whether the Fermi energy lies in the valence or conduction band.
The geometry of Schroedinger symmetry in non-relativistic CFT
Duval, C. Hassaine, M. Horvathy, P.A.
2009-05-15
The non-relativistic conformal 'Schroedinger' symmetry of some gravity backgrounds proposed recently in the AdS/CFT context, is explained in the 'Bargmann framework'. The formalism incorporates the Equivalence Principle. Newton-Hooke conformal symmetries, which are analogs of those of Schroedinger in the presence of a negative cosmological constant, are discussed in a similar way. Further examples include topologically massive gravity with negative cosmological constant and the Madelung hydrodynamical description.
Süllow, S; Maksimov, I; Otop, A; Litterst, F J; Perucchi, A; Degiorgi, L; Mydosh, J A
2004-12-31
We present a detailed study of the electronic transport properties on a single crystalline specimen of the moderately disordered heavy-fermion system URh2Ge2. For this material, we find glassy electronic transport in a single crystalline compound. We derive the temperature dependence of the electrical conductivity and establish metallicity by means of optical conductivity and Hall effect measurements. The overall behavior of the electronic transport properties closely resembles that of metallic glasses, with at low temperatures an additional minor spin disorder contribution. We argue that this glassy electronic behavior in a crystalline compound reflects the enhancement of disorder effects as a consequence of strong electronic correlations. PMID:15698001
On the non-relativistic limit of charge conjugation in QED
NASA Astrophysics Data System (ADS)
Carballo Pérez, B.; Socolovsky, M.
2011-01-01
Even if at the level of the non-relativistic limit of full QED, C is not a symmetry, the limit of this operation does exist for the particular case when the electromagnetic field is considered a classical external object coupled to the Dirac field. This result extends the one obtained when fermions are described by the Schrödinger-Pauli equation. We give the expressions for both the C matrix and the hat{{C}} operator for Galilean electrons and positrons interacting with the external electromagnetic field. The result is relevant in relation to recent experiments with antihydrogen.
Curved non-relativistic spacetimes, Newtonian gravitation and massive matter
Geracie, Michael Prabhu, Kartik Roberts, Matthew M.
2015-10-15
There is significant recent work on coupling matter to Newton-Cartan spacetimes with the aim of investigating certain condensed matter phenomena. To this end, one needs to have a completely general spacetime consistent with local non-relativistic symmetries which supports massive matter fields. In particular, one cannot impose a priori restrictions on the geometric data if one wants to analyze matter response to a perturbed geometry. In this paper, we construct such a Bargmann spacetime in complete generality without any prior restrictions on the fields specifying the geometry. The resulting spacetime structure includes the familiar Newton-Cartan structure with an additional gauge field which couples to mass. We illustrate the matter coupling with a few examples. The general spacetime we construct also includes as a special case the covariant description of Newtonian gravity, which has been thoroughly investigated in previous works. We also show how our Bargmann spacetimes arise from a suitable non-relativistic limit of Lorentzian spacetimes. In a companion paper [M. Geracie et al., e-print http://arxiv.org/abs/1503.02680 ], we use this Bargmann spacetime structure to investigate the details of matter couplings, including the Noether-Ward identities, and transport phenomena and thermodynamics of non-relativistic fluids.
Lake, M.L.
1981-08-01
Experiments were undertaken to determine electron impact cross sections of atoms in metastable states. One or two electron guns were used to first produce atoms in metastable states, then further excite these atoms to other levels. Limits on certain cross sections of helium atoms were obtained, but the detection limits of the apparatus prevented exhaustive study. Excitation functions and cross sections of xenon were obtained in the wavelength range from 3000 A to 9000 A.
Crespo Lopez-Urrutia, J.R.; Beiersdorfer, P.; Savin, D.; Widmann, K.
1996-07-01
We report the first direct laboratory measurement of the spontaneous emission due to the hyperfine splitting of the ground state of a highly charged hydrogenlike ion excited by electron collisions. The transition between the {ital F}=4 and {ital F}=3 levels of the 1{ital s}{sup 2}{ital S}{sub 1/2} configuration of hydrogenlike {sup 165}Ho{sup 65+} was observed and its wavelength was determined to 5726.4{plus_minus}1.5. After taking into account relativistic, nuclear charge distribution, Bohr-Weisskopf, and QED corrections, we observe a significant deviation from commonly tabulated values of the nuclear dipole magnetic moment of this nucleus. {copyright} {ital 1996 The American Physical Society.}
Continuity properties of the semi-group and its integral kernel in non-relativistic QED
NASA Astrophysics Data System (ADS)
Matte, Oliver
2016-07-01
Employing recent results on stochastic differential equations associated with the standard model of non-relativistic quantum electrodynamics by B. Güneysu, J. S. Møller, and the present author, we study the continuity of the corresponding semi-group between weighted vector-valued Lp-spaces, continuity properties of elements in the range of the semi-group, and the pointwise continuity of an operator-valued semi-group kernel. We further discuss the continuous dependence of the semi-group and its integral kernel on model parameters. All these results are obtained for Kato decomposable electrostatic potentials and the actual assumptions on the model are general enough to cover the Nelson model as well. As a corollary, we obtain some new pointwise exponential decay and continuity results on elements of low-energetic spectral subspaces of atoms or molecules that also take spin into account. In a simpler situation where spin is neglected, we explain how to verify the joint continuity of positive ground state eigenvectors with respect to spatial coordinates and model parameters. There are no smallness assumptions imposed on any model parameter.
Shrestha, Kushal; Jakubikova, Elena
2015-08-20
Light-harvesting antennas are protein-pigment complexes that play a crucial role in natural photosynthesis. The antenna complexes absorb light and transfer energy to photosynthetic reaction centers where charge separation occurs. This work focuses on computational studies of the electronic structure of the pigment networks of light-harvesting complex I (LH1), LH1 with the reaction center (RC-LH1), and light-harvesting complex II (LH2) found in purple bacteria. As the pigment networks of LH1, RC-LH1, and LH2 contain thousands of atoms, conventional density functional theory (DFT) and ab initio calculations of these systems are not computationally feasible. Therefore, we utilize DFT in conjunction with the energy-based fragmentation with molecular orbitals method and a semiempirical approach employing the extended Hückel model Hamiltonian to determine the electronic properties of these pigment assemblies. Our calculations provide a deeper understanding of the electronic structure of natural light-harvesting complexes, especially their pigment networks, which could assist in rational design of artificial photosynthetic devices. PMID:26215074
A Remark on the Ground State Energy of Bosonic Atoms
NASA Astrophysics Data System (ADS)
Hogreve, H.
2011-08-01
Monotonicity properties of the ground state energy of bosonic atoms as established in a recent paper by M.K.H. Kiessling [J. Stat. Phys. 139:1063 (2009)] are studied. Symmetry and scaling arguments lead to a more direct proof of a slightly stronger result of this monotonicity and the behavior of the ground state energy as a function of the number of bosonic electrons. Furthermore, invoking appropriate lower and upper bounds on two-electron systems, the stability of the bosonics He- ion is rigorously demonstrated.
Anderson, Nickolas H; Odoh, Samuel O; Williams, Ursula J; Lewis, Andrew J; Wagner, Gregory L; Lezama Pacheco, Juan; Kozimor, Stosh A; Gagliardi, Laura; Schelter, Eric J; Bart, Suzanne C
2015-04-15
The electronic structures of a series of highly reduced uranium complexes bearing the redox-active pyridine(diimine) ligand, (Mes)PDI(Me) ((Mes)PDI(Me) = 2,6-(2,4,6-Me3-C6H2-N═CMe)2C5H3N) have been investigated. The complexes, ((Mes)PDI(Me))UI3(THF) (1), ((Mes)PDI(Me))UI2(THF)2 (2), [((Mes)PDI(Me))UI]2 (3), and [((Mes)PDI(Me))U(THF)]2 (4), were examined using electronic and X-ray absorption spectroscopies, magnetometry, and computational analyses. Taken together, these studies suggest that all members of the series contain uranium(IV) centers with 5f (2) configurations and reduced ligand frameworks, specifically [(Mes)PDI(Me)](•/-), [(Mes)PDI(Me)](2-), [(Mes)PDI(Me)](3-) and [(Mes)PDI(Me)](4-), respectively. In the cases of 2, 3, and 4 no unpaired spin density was found on the ligands, indicating a singlet diradical ligand in monomeric 2 and ligand electron spin-pairing through dimerization in 3 and 4. Interaction energies, representing enthalpies of dimerization, of -116.0 and -144.4 kcal mol(-1) were calculated using DFT for the monomers of 3 and 4, respectively, showing there is a large stabilization gained by dimerization through uranium-arene bonds. Highlighted in these studies is compound 4, bearing a previously unobserved pyridine(diimine) tetraanion, that was uniquely stabilized by backbonding between uranium cations and the η(5)-pyridyl ring. PMID:25830409
SIMULATIONS AND THEORY OF ION INJECTION AT NON-RELATIVISTIC COLLISIONLESS SHOCKS
Caprioli, Damiano; Pop, Ana-Roxana; Spitkovsky, Anatoly
2015-01-10
We use kinetic hybrid simulations (kinetic ions-fluid electrons) to characterize the fraction of ions that are accelerated to non-thermal energies at non-relativistic collisionless shocks. We investigate the properties of the shock discontinuity and show that shocks propagating almost along the background magnetic field (quasi-parallel shocks) reform quasi-periodically on ion cyclotron scales. Ions that impinge on the shock when the discontinuity is the steepest are specularly reflected. This is a necessary condition for being injected, but it is not sufficient. Also, by following the trajectories of reflected ions, we calculate the minimum energy needed for injection into diffusive shock acceleration, as a function of the shock inclination. We construct a minimal model that accounts for the ion reflection from quasi-periodic shock barrier, for the fraction of injected ions, and for the ion spectrum throughout the transition from thermal to non-thermal energies. This model captures the physics relevant for ion injection at non-relativistic astrophysical shocks with arbitrary strengths and magnetic inclinations, and represents a crucial ingredient for understanding the diffusive shock acceleration of cosmic rays.
March, N H; Nagy, A
2008-11-21
Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell. PMID:19026052
Feasibility of OTR imaging of non-relativistic ions at GSI
Lumpkin, A.H.; /Fermilab
2011-03-01
The feasibility of using the optical transition radiation (OTR) generated as a 11.4- to 300-MeV/u ion beam passes through a single metal conducting plane for a minimally intercepting beam profile monitor for GSI/Darmstadt has been evaluated for the first time. Although these are non-relativistic beams, their beta and gamma values are similar to the 80-keV electron-beam imaging studies previously done on the CTF3 injector. With anticipated beam intensities of 10{sup 9} to 10{sup 11} particles per pulse and the predicted charge-squared dependence of OTR, the ion charge state becomes a critical factor for photon production. The OTR signal from the ion charge integrated over the video field time should be comparable to or larger than the CTF3 electron case. These signal strengths will allow a series of experiments to be done that should further elucidate the working regime of this technique.
Constrained Path Quantum Monte Carlo Method for Fermion Ground States
NASA Astrophysics Data System (ADS)
Zhang, Shiwei; Carlson, J.; Gubernatis, J. E.
1995-05-01
We propose a new quantum Monte Carlo algorithm to compute fermion ground-state properties. The ground state is projected from an initial wave function by a branching random walk in an over-complete basis space of Slater determinants. By constraining the determinants according to a trial wave function \\|ΨT>, we remove the exponential decay of signal-to-noise ratio characteristic of the sign problem. The method is variational and is exact if \\|ΨT> is exact. We report results on the two-dimensional Hubbard model up to size 16×16, for various electron fillings and interaction strengths.
Estimation of beryllium ground state energy by Monte Carlo simulation
NASA Astrophysics Data System (ADS)
Kabir, K. M. Ariful; Halder, Amal
2015-05-01
Quantum Monte Carlo method represent a powerful and broadly applicable computational tool for finding very accurate solution of the stationary Schrödinger equation for atoms, molecules, solids and a variety of model systems. Using variational Monte Carlo method we have calculated the ground state energy of the Beryllium atom. Our calculation are based on using a modified four parameters trial wave function which leads to good result comparing with the few parameters trial wave functions presented before. Based on random Numbers we can generate a large sample of electron locations to estimate the ground state energy of Beryllium. Our calculation gives good estimation for the ground state energy of the Beryllium atom comparing with the corresponding exact data.
Estimation of beryllium ground state energy by Monte Carlo simulation
Kabir, K. M. Ariful; Halder, Amal
2015-05-15
Quantum Monte Carlo method represent a powerful and broadly applicable computational tool for finding very accurate solution of the stationary Schrödinger equation for atoms, molecules, solids and a variety of model systems. Using variational Monte Carlo method we have calculated the ground state energy of the Beryllium atom. Our calculation are based on using a modified four parameters trial wave function which leads to good result comparing with the few parameters trial wave functions presented before. Based on random Numbers we can generate a large sample of electron locations to estimate the ground state energy of Beryllium. Our calculation gives good estimation for the ground state energy of the Beryllium atom comparing with the corresponding exact data.
Engineering the Ground State of Complex Oxides
NASA Astrophysics Data System (ADS)
Meyers, Derek Joseph
Transition metal oxides featuring strong electron-electron interactions have been at the forefront of condensed matter physics research in the past few decades due to the myriad of novel and exciting phases derived from their competing interactions. Beyond their numerous intriguing properties displayed in the bulk they have also shown to be quite susceptible to externally applied perturbation in various forms. The dominant theme of this work is the exploration of three emerging methods for engineering the ground states of these materials to access both their applicability and their deficiencies. The first of the three methods involves a relatively new set of compounds which adhere to a unique paradigm in chemical doping, a-site ordered perovskites. These compounds are iso-structural, i.e. constant symmetry, despite changing the dopant ions. We find that these materials, featuring Cu at the doped A-site, display the Zhang-Rice state, to varying degrees, found in high temperature superconducting cuprates, with the choice of B-site allowing "self-doping" within the material. Further, we find that within CaCu3Ir 4O12 the Cu gains a localized magnetic moment and leads to the experimentally observed heavy fermion state in the materials, one of only two such non-f-electron heavy fermion materials. Next, epitaxial constraint is used to modify the ground state of the rare-earth nickelates in ultra thin film form. Application of compressive (tensile) strain is found to suppress (maintain) the temperature at which the material goes through a Mott metal-insulator transition. Further, while for EuNiO3 thin films the typical bulk-like magnetic and charge ordering is found to occur, epitaxial strain is found to suppress the charge ordering in NdNiO3 thin films due to pinning to the substrate and the relatively weak tendency to monoclinically distort. Finally, the creation of superlattices of EuNiO3 and LaNiO3 was shown to not only allow the selection of the temperature at which
Non-relativistic metrics from back-reacting fermions
NASA Astrophysics Data System (ADS)
Hung, Ling-Yan; Jatkar, Dileep P.; Sinha, Aninda
2011-01-01
It has recently been pointed out that under certain circumstances the back-reaction of charged, massive Dirac fermions causes important modifications to AdS2 spacetimes arising as the near-horizon geometry of extremal black holes. In a WKB approximation, the modified geometry becomes a non-relativistic Lifshitz spacetime. In three dimensions, it is known that integrating out charged, massive fermions gives rise to gravitational and Maxwell Chern-Simons terms. We show that Schrödinger (warped AdS3) spacetimes exist as solutions to a gravitational and Maxwell Chern-Simons theory with a cosmological constant. Motivated by this, we look for warped AdS3 or Schrödinger metrics as exact solutions to a fully back-reacted theory containing Dirac fermions in three and four dimensions. We work out the dynamical exponent in terms of the fermion mass and generalize this result to arbitrary dimensions.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; Ramos, Mike; Trouw, Frans; Zhu, Jian -Xin; Haule, Kristjan; Kotliar, Gabriel; Bauer, Eric D.
2015-07-10
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. In addition, our study reveals that the ground state of plutonium is governed by valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; Ramos, Mike; Trouw, Frans; Zhu, Jian-Xin; Haule, Kristjan; Kotliar, Gabriel; Bauer, Eric D.
2015-01-01
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. Our study reveals that the ground state of plutonium is governed by valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials. PMID:26601219
Variable energy, high flux, ground-state atomic oxygen source
NASA Technical Reports Server (NTRS)
Chutjian, Ara (Inventor); Orient, Otto J. (Inventor)
1987-01-01
A variable energy, high flux atomic oxygen source is described which is comprised of a means for producing a high density beam of molecules which will emit O(-) ions when bombarded with electrons; a means of producing a high current stream of electrons at a low energy level passing through the high density beam of molecules to produce a combined stream of electrons and O(-) ions; means for accelerating the combined stream to a desired energy level; means for producing an intense magnetic field to confine the electrons and O(-) ions; means for directing a multiple pass laser beam through the combined stream to strip off the excess electrons from a plurality of the O(-) ions to produce ground-state O atoms within the combined stream; electrostatic deflection means for deflecting the path of the O(-) ions and the electrons in the combined stream; and, means for stopping the O(-) ions and the electrons and for allowing only the ground-state O atoms to continue as the source of the atoms of interest. The method and apparatus are also adaptable for producing other ground-state atoms and/or molecules.
Triplet (S = 1) Ground State Aminyl Diradical
Rajca, Andrzej; Shiraishi, Kouichi; Pink, Maren; Rajca, Suchada
2008-04-02
Aminyl diradical, which is stable in solution at low temperatures, is prepared. EPR spectra and SQUID magnetometry indicate that the diradical is planar and it possesses triplet ground state, with strong ferromagnetic coupling.
A signed particle formulation of non-relativistic quantum mechanics
Sellier, Jean Michel
2015-09-15
A formulation of non-relativistic quantum mechanics in terms of Newtonian particles is presented in the shape of a set of three postulates. In this new theory, quantum systems are described by ensembles of signed particles which behave as field-less classical objects which carry a negative or positive sign and interact with an external potential by means of creation and annihilation events only. This approach is shown to be a generalization of the signed particle Wigner Monte Carlo method which reconstructs the time-dependent Wigner quasi-distribution function of a system and, therefore, the corresponding Schrödinger time-dependent wave-function. Its classical limit is discussed and a physical interpretation, based on experimental evidences coming from quantum tomography, is suggested. Moreover, in order to show the advantages brought by this novel formulation, a straightforward extension to relativistic effects is discussed. To conclude, quantum tunnelling numerical experiments are performed to show the validity of the suggested approach.
Nonmagnetic ground state of PuO2
NASA Astrophysics Data System (ADS)
Shick, A. B.; Kolorenč, J.; Havela, L.; Gouder, T.; Caciuffo, R.
2014-01-01
The correlated band theory implemented as a combination of the local density approximation with the exact diagonalization of the Anderson impurity model is applied to PuO2. We obtain an insulating electronic structure consistent with the experimental photoemission spectra. The calculations yield a band gap of 1.8 eV and a nonmagnetic singlet ground state that is characterized by a noninteger filling of the plutonium f shell (nf≈4.5). Due to sizable hybridization of the f shell with the p states of oxygen, the ground state is more complex than the four-electron Russell-Saunders 5I4 manifold split by the crystal field. The inclusion of hybridization improves the agreement between the theory and experiment for the magnetic susceptibility.
Ground-state energy and relativistic corrections for positronium hydride
Bubin, Sergiy; Varga, Kalman
2011-07-15
Variational calculations of the ground state of positronium hydride (HPs) are reported, including various expectation values, electron-positron annihilation rates, and leading relativistic corrections to the total and dissociation energies. The calculations have been performed using a basis set of 4000 thoroughly optimized explicitly correlated Gaussian basis functions. The relative accuracy of the variational energy upper bound is estimated to be of the order of 2x10{sup -10}, which is a significant improvement over previous nonrelativistic results.
Numerical Evaluation of 2D Ground States
NASA Astrophysics Data System (ADS)
Kolkovska, Natalia
2016-02-01
A ground state is defined as the positive radial solution of the multidimensional nonlinear problem
The combined non-relativistic and quasi-neutral limit of two-fluid Euler-Maxwell equations
NASA Astrophysics Data System (ADS)
Li, Yachun; Peng, Yue-Jun; Xi, Shuai
2015-12-01
We consider two-fluid Euler-Maxwell equations for magnetized plasmas composed of electrons and ions. By using the method of asymptotic expansions, we analyze the combined non-relativistic and quasi-neutral limit for periodic problems with well-prepared initial data. It is shown that the small parameter problems have a unique solution existing in a finite time interval where the corresponding limit problems (compressible Euler equations) have smooth solutions. The proof is based on energy estimates for symmetrizable hyperbolic equations and on the exploration of the coupling between the Euler equations and the Maxwell equations.
Ground state number fluctuations of trapped particles
NASA Astrophysics Data System (ADS)
Tran, Muoi N.
This thesis encompasses a number of problems related to the number fluctuations from the ground state of ideal particles in different statistical ensembles. In the microcanonical ensemble most of these problems may be solved using number theory. Given an energy E, the well-known problem of finding the number of ways of distributing N bosons over the excited levels of a one-dimensional harmonic spectrum, for instance, is equivalent to the number of restricted partitions of E. As a result, the number fluctuation from the ground state in the microcanonical ensemble for this system may be found analytically. When the particles are fermions instead of bosons, however, it is difficult to calculate the exact ground state number fluctuation because the fermionic ground state consists of many levels. By breaking up the energy spectrum into particle and hole sectors, and mapping the problem onto the classic number partitioning theory, we formulate a method of calculating the particle number fluctuation from the ground state in the microcanonical ensemble for fermions. The same quantity is calculated for particles interacting via an inverse-square pairwise interaction in one dimension. In the canonical ensemble, an analytical formula for the ground state number fluctuation is obtained by using the mapping of this system onto a system of noninteracting particles obeying the Haldane-Wu exclusion statistics. In the microcanonical ensemble, however, the result can be obtained only for a limited set of values of the interacting strength parameter. Usually, for a discrete set of a mean-field single-particle quantum spectrum and in the microcanonical ensemble, there are many combinations of exciting particles from the ground state. The spectrum given by the logarithms of the prime number sequence, however, is a counterexample to this rule. Here, as a consequence of the fundamental theorem of arithmetic, there is a one-to-one correspondence between the microstate and the macrostate
Trapped antihydrogen in its ground state.
Gabrielse, G; Kalra, R; Kolthammer, W S; McConnell, R; Richerme, P; Grzonka, D; Oelert, W; Sefzick, T; Zielinski, M; Fitzakerley, D W; George, M C; Hessels, E A; Storry, C H; Weel, M; Müllers, A; Walz, J
2012-03-16
Antihydrogen atoms (H¯) are confined in an Ioffe trap for 15-1000 s-long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons (p¯) and positrons (e(+)) interact, 5±1 simultaneously confined ground-state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped H¯ are critical if laser cooling of trapped H¯ is to be demonstrated and spectroscopic studies at interesting levels of precision are to be carried out. PMID:22540471
Mizel, Ari
2004-07-01
Ground-state quantum computers mimic quantum-mechanical time evolution within the amplitudes of a time-independent quantum state. We explore the principles that constrain this mimicking. A no-cloning argument is found to impose strong restrictions. It is shown, however, that there is flexibility that can be exploited using quantum teleportation methods to improve ground-state quantum computer design.
Kohn-Sham Theory for Ground-State Ensembles
Ullrich, C. A.; Kohn, W.
2001-08-27
An electron density distribution n(r) which can be represented by that of a single-determinant ground state of noninteracting electrons in an external potential v(r) is called pure-state v -representable (P-VR). Most physical electronic systems are P-VR. Systems which require a weighted sum of several such determinants to represent their density are called ensemble v -representable (E-VR). This paper develops formal Kohn-Sham equations for E-VR physical systems, using the appropriate coupling constant integration. It also derives local density- and generalized gradient approximations, and conditions and corrections specific to ensembles.
a Variational Ground State for the Fractional Quantum Hall Effect.
NASA Astrophysics Data System (ADS)
Galejs, Robert Julian
1987-09-01
The fractional quantum Hall effect has aroused much interest in recent years. A large portion of the research in this field has centered on the theoretical understanding of the ground state properties of a system of two-dimensional electrons in a perpendicular magnetic field. One of the most successful models for such a system is that of Laughlin, who proposed a trial wavefunction to model the ground state for certain electron densities. The present work examines the ground state of this system variationally for three and four electrons. The ground state was modeled as a sum of Slater determinants composed of one-electron functions from the lowest Landau level. This wavefunction was placed on a disk of neutralizing charge and the coefficients of the determinants varied to minimize the energy. This variational wavefunction may be compared directly with Laughlin's, as well as model densities not described by Laughlin. The energy per electron was found to vary smoothly as a function of filling factor except at discrete points where there was an upward cusp. Downward cusps, as found by other investigators, were not found in this work. In the smooth portions, the wavefunction is incompressible whereas at the cusps, the wavefunction undergoes a drastic change. In the presence of impurities, these upward cusps smooth out and the wavefunction is now charge-density-wave -like near the former location of the cusps. This variation between incompressible and charge-density-wave behavior may give an explanation of the behavior of the Hall plateau widths as a function of impurity concentration. At a filling factor of 1/3 it was found that the Laughlin wavefunction is a very good approximation to the ground state, giving a very large overlap with and only a slightly higher energy than the variational state calculated here. Laughlin's excited states appear to be a good approximation as well, although the details of their charge density may not be. A new class of wavefunctions was
Cavity optomechanics -- beyond the ground state
NASA Astrophysics Data System (ADS)
Meystre, Pierre
2011-05-01
The coupling of coherent optical systems to micromechanical devices, combined with breakthroughs in nanofabrication and in ultracold science, has opened up the exciting new field of cavity optomechanics. Cooling of the vibrational motion of a broad range on oscillating cantilevers and mirrors near their ground state has been demonstrated, and the ground state of at least one such system has now been reached. Cavity optomechanics offers much promise in addressing fundamental physics questions and in applications such as the detection of feeble forces and fields, or the coherent control of AMO systems and of nanoscale electromechanical devices. However, these applications require taking cavity optomechanics ``beyond the ground state.'' This includes the generation and detection of squeezed and other non-classical states, the transfer of squeezing between electromagnetic fields and motional quadratures, and the development of measurement schemes for the characterization of nanomechanical structures. The talk will present recent ``beyond ground state'' developments in cavity optomechanics. We will show how the magnetic coupling between a mechanical membrane and a BEC - or between a mechanical tuning fork and a nanoscale cantilever - permits to control and monitor the center-of-mass position of the mechanical system, and will comment on the measurement back-action on the membrane motion. We will also discuss of state transfer between optical and microwave fields and micromechanical devices. Work done in collaboration with Dan Goldbaum, Greg Phelps, Keith Schwab, Swati Singh, Steve Steinke, Mehmet Tesgin, and Mukund Vengallatore and supported by ARO, DARPA, NSF, and ONR.
Constrained path Monte Carlo method for fermion ground states
Zhang, S. |; Carlson, J.; Gubernatis, J.E.
1997-03-01
We describe and discuss a recently proposed quantum Monte Carlo algorithm to compute the ground-state properties of various systems of interacting fermions. In this method, the ground state is projected from an initial wave function by a branching random walk in an overcomplete basis of Slater determinants. By constraining the determinants according to a trial wave function {vert_bar}{psi}{sub T}{r_angle}, we remove the exponential decay of signal-to-noise ratio characteristic of the sign problem. The method is variational and is exact if {vert_bar}{psi}{sub T}{r_angle} is exact. We illustrate the method by describing in detail its implementation for the two-dimensional one-band Hubbard model. We show results for lattice sizes up to 16{times}16 and for various electron fillings and interaction strengths. With simple single-determinant wave functions as {vert_bar}{psi}{sub T}{r_angle}, the method yields accurate (often to within a few percent) estimates of the ground-state energy as well as correlation functions, such as those for electron pairing. We conclude by discussing possible extensions of the algorithm. {copyright} {ital 1997} {ital The American Physical Society}
Constrained path Monte Carlo method for fermion ground states
NASA Astrophysics Data System (ADS)
Zhang, Shiwei; Carlson, J.; Gubernatis, J. E.
1997-03-01
We describe and discuss a recently proposed quantum Monte Carlo algorithm to compute the ground-state properties of various systems of interacting fermions. In this method, the ground state is projected from an initial wave function by a branching random walk in an overcomplete basis of Slater determinants. By constraining the determinants according to a trial wave function \\|ψT>, we remove the exponential decay of signal-to-noise ratio characteristic of the sign problem. The method is variational and is exact if \\|ψT> is exact. We illustrate the method by describing in detail its implementation for the two-dimensional one-band Hubbard model. We show results for lattice sizes up to 16×16 and for various electron fillings and interaction strengths. With simple single-determinant wave functions as \\|ψT>, the method yields accurate (often to within a few percent) estimates of the ground-state energy as well as correlation functions, such as those for electron pairing. We conclude by discussing possible extensions of the algorithm.
Room temperature skyrmion ground state stabilized through interlayer exchange coupling
Chen, Gong Schmid, Andreas K.; Mascaraque, Arantzazu; N'Diaye, Alpha T.
2015-06-15
Possible magnetic skyrmion device applications motivate the search for structures that extend the stability of skyrmion spin textures to ambient temperature. Here, we demonstrate an experimental approach to stabilize a room temperature skyrmion ground state in chiral magnetic films via exchange coupling across non-magnetic spacer layers. Using spin polarized low-energy electron microscopy to measure all three Cartesian components of the magnetization vector, we image the spin textures in Fe/Ni films. We show how tuning the thickness of a copper spacer layer between chiral Fe/Ni films and perpendicularly magnetized Ni layers permits stabilization of a chiral stripe phase, a skyrmion phase, and a single domain phase. This strategy to stabilize skyrmion ground states can be extended to other magnetic thin film systems and may be useful for designing skyrmion based spintronics devices.
Ground-state phases of polarized deuterium species
Panoff, R.M.; Clark, J.W.
1987-10-01
Microscopic prediction of the ground-state phase of electron-spin-aligned bulk atomic deuterium (Darrow-down) is attempted, based on the variational Monte Carlo method. The accurate pair potential of Kolos and Wolniewicz is assumed, and three versions of Darrow-down are considered, which, respectively, involve one, two, and three equally occupied nuclear spin states. The most definitive results on the zero-temperature equations of state of these systems are obtained with optimized ground-state trial wave functions incorporating Jastrow pair correlations, triplet correlations, and momentum-dependent backflow effects. The species Darrow-down/sub 3/ is bound already at the pure Jastrow level, while the energy expectation value of Darrow-down/sub 2/ dips below zero upon supplementing the Jastrow description by triplets and momentum-dependent backflow. The variational energy of Darrow-down/sub 1/ remains positive under all current refinements of the ground-state trial function. We conclude that the systems Darrow-down/sub 3/ and Darrow-down/sub 2/, if they could be manufactured and stabilized at relevant densities, would be Fermi liquids at sufficiently low temperature; on the other hand, it is likely that Darrow-down/sub 1/ would remain gaseous down to absolute zero.
Magnetic properties of ground-state mesons
NASA Astrophysics Data System (ADS)
Šimonis, V.
2016-04-01
Starting with the bag model a method for the study of the magnetic properties (magnetic moments, magnetic dipole transition widths) of ground-state mesons is developed. We calculate the M1 transition moments and use them subsequently to estimate the corresponding decay widths. These are compared with experimental data, where available, and with the results obtained in other approaches. Finally, we give the predictions for the static magnetic moments of all ground-state vector mesons including those containing heavy quarks. We have a good agreement with experimental data for the M1 decay rates of light as well as heavy mesons. Therefore, we expect our predictions for the static magnetic properties ( i.e., usual magnetic moments) to be of sufficiently high quality, too.
On the ground state of quantum gravity
NASA Astrophysics Data System (ADS)
Cacciatori, S.; Preparata, G.; Rovelli, S.; Spagnolatti, I.; Xue, S.-S.
1998-05-01
In order to gain insight into the possible ground state of quantized Einstein's gravity, we have devised a variational calculation of the energy of the quantum gravitational field in an open space, as measured by an asymptotic observer living in an asymptotically flat space-time. We find that for quantum gravity (QG) it is energetically favourable to perform its quantum fluctuations not upon flat space-time but around a ``gas'' of wormholes, whose size is the Planck length ap (ap~=10-33 cm). As a result, assuming such configuration to be a good approximation to the true ground state of quantum gravity, space-time, the arena of physical reality, turns out to be well described by Wheeler's Quantum Foam and adequately modeled by a space-time lattice with lattice constant ap, the Planck lattice. All rights reserved
Ground-state energy of nuclear matter
NASA Astrophysics Data System (ADS)
Baker, George A., Jr.; Benofy, L. P.; Fortes, Mauricio
1988-07-01
The low-density expansion of the ground-state energy for spin-dependent forces is given, through order k6F for the ladder approximation and through order k6FlnkF for the complete energy, in terms of derivatives with respect to the strength of the attractive part of the interaction defined by the Baker-Hind-Kahane potential. The ladder approximation is also computed by the numerical solution of the K-matrix equation. The resulting series gives a satisfactory representation of the energy at interesting densities. Using Padé extrapolation techniques, both in the density and in the attractive part of the interaction, we obtain the ground-state energy of nuclear matter.
Individual Atoms in their Quantum Ground State
NASA Astrophysics Data System (ADS)
Schwartz, Eyal; Sompet, Pimonpan; Fung, Yin Hsien; Andersen, Mikkel F.
2016-05-01
An ultimate control of pure quantum states is an excellent platform for various quantum science and engineering. In this work, we perform quantum manipulation of individual Rubidium atoms in a tightly focus optical tweezer in order to cool them into their vibrational ground state via Raman sideband cooling. Our experimental scheme involves a combination of Raman sideband transitions and optical pumping of the atoms that couples two magnetic field sublevels indifferent to magnetic noise thus providing a much longer atomic coherence time compared to previous cooling schemes. By installing most of the atoms in their ground state, we managed to achieve two-dimensional cooling on the way to create a full nil entropy quantum state of single atoms and single molecules. We acknowledge the Marsden Fund, CORE and DWC for their support.
Ground state degeneracy of interacting spinless fermions
NASA Astrophysics Data System (ADS)
Wei, Zhong-Chao; Han, Xing-Jie; Xie, Zhi-Yuan; Xiang, Tao
2015-10-01
We propose an eigenoperator scheme to study the lattice model of interacting spinless fermions at half filling and show that this model possesses a hidden form of reflection positivity in its Majorana fermion representation. Based on this observation, we prove rigourously that the ground state of this model is either unique or doubly degenerate if the lattice size N is even, and is always doubly degenerate if N is odd. This proof holds in all dimensions with arbitrary lattice structures.
Ground state searches in fcc intermetallics
Wolverton, C.; de Fontaine, D. ); Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)
1991-12-01
A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.
The valence-fluctuating ground state of plutonium
Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; Abernathy, Douglas L.; Lumsden, Mark D.; Lawrence, John M.; Thompson, Joe D.; Lander, Gerard H.; Mitchell, Jeremy N.; Richmond, Scott; et al
2015-07-10
A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. In addition, our study reveals that the ground state of plutonium is governed bymore » valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.« less
NASA Astrophysics Data System (ADS)
Fu, X.; Waters, T.; Gary, S. P.
2014-12-01
Collisionless space plasmas often deviate from Maxwellian-like velocity distributions. To study kinetic waves and instabilities in such plasmas, the dispersion relation, which depends on the velocity distribution, needs to be solved numerically. Most current dispersion solvers (e.g. WHAMP) take advantage of mathematical properties of the Gaussian (or generalized Lorentzian) function, and assume that the velocity distributions can be modeled by a combination of several drift-Maxwellian (or drift-Lorentzian) components. In this study we are developing a kinetic dispersion solver that admits nearly arbitrary non-relativistic parallel velocity distributions. A key part of any dispersion solver is the evaluation of a Hilbert transform of the velocity distribution function and its derivative along Landau contours. Our new solver builds upon a recent method to compute the Hilbert transform accurately and efficiently using the fast Fourier transform, while simultaneously treating the singularities arising from resonances analytically. We have benchmarked our new solver against other codes dealing with Maxwellian distributions. As an example usage of our code, we will show results for several instabilities that occur for electron velocity distributions observed in the solar wind.
Particle Acceleration and Magnetic Field Amplification at Non-relativistic Collisionless Shocks
NASA Astrophysics Data System (ADS)
Caprioli, Damiano; Spitkovsky, A.
2013-04-01
We investigate the dynamics of non-relativistic, collisionless shocks by using unprecedentedly large 2D and 3D hybrid (kinetic ions - fluid electrons) simulations. We find that, at parallel shocks, ions are efficiently accelerated via first-order Fermi mechanism; the current driven by the energetic particles propagating into the upstream medium excites plasma instabilities that strongly perturb the initial electromagnetic configuration. In particular, the filamentation instability produces tubular, underdense, magnetic-field-depleted cavities, in which accelerated particles are channeled. These structures grow while being advected with the fluid, effectively corrugating the shock surface and triggering turbulent motions in the downstream. The net result is a marked increase of the magnetic field, both ahead and behind the shock, in agreement with the high levels of magnetization inferred at the blast waves of young supernova remnants. We also discuss the dependence of the ion acceleration efficiency on the orientation and on the strength of the upstream magnetic field, finding that ions are preferentially accelerated at parallel, fast shocks (i.e., shocks propagating along the initial magnetic field, with velocities much larger than the Alfvén speed).
Two different ground states in K-intercalated polyacenes
NASA Astrophysics Data System (ADS)
Phan, Quynh T. N.; Heguri, Satoshi; Tamura, Hiroyuki; Nakano, Takehito; Nozue, Yasuo; Tanigaki, Katsumi
2016-02-01
The electronic states of potassium- (K-) intercalated zigzag-type polycyclic aromatic (PLA) hydrocarbon [polyacene PLAs] Kx(PLAs ) are studied for a series of the four smallest molecules: naphthalene (NN), anthracene (AN), tetracene (TN), and pentacene (PN), focusing on their 1:1 stoichiometric phases. Clear experimental differences are identified between the first group [K1(NN ) and K1(AN ) ] and the second group [K1(TN ) and K1(PN ) ] by magnetic, vibrational, and optical measurements. The first group is categorized as a Mott insulator with an antiferromagnetic ground state with energy of ˜10 meV, whereas the second group is classified as a band insulator via dimer formation due to the spin Peierls instability. In the latter system, the first thermally accessible triplet states are located far apart from the singlet ground states and are not detected by electron spin-resonance spectroscopy until 300 K being very different from what is observed for the hole-doped PN reported earlier. The results give a new systematic understanding on the electronic states of electron-doped PLAs sensitive to the energetic balance among on-site Coulomb repulsion, bandwidth, and the Peierls instability.
Effect of disorder on the ground-state properties of graphene
NASA Astrophysics Data System (ADS)
Asgari, R.; Vazifeh, M. M.; Ramezanali, M. R.; Davoudi, E.; Tanatar, B.
2008-03-01
We calculate the ground-state energy of Dirac electrons in graphene in the presence of disorder. We take randomly distributed charged impurities at a fixed distance from the graphene sheet and surface fluctuations (ripples) as the main scattering mechanisms. A mode-coupling approach to the scattering rate and random-phase approximation for the ground-state energy incorporating the many-body interactions and the disorder effects yields good agreement with the experimental inverse compressibility.
Ground state fidelity from tensor network representations.
Zhou, Huan-Qiang; Orús, Roman; Vidal, Guifre
2008-02-29
For any D-dimensional quantum lattice system, the fidelity between two ground state many-body wave functions is mapped onto the partition function of a D-dimensional classical statistical vertex lattice model with the same lattice geometry. The fidelity per lattice site, analogous to the free energy per site, is well defined in the thermodynamic limit and can be used to characterize the phase diagram of the model. We explain how to compute the fidelity per site in the context of tensor network algorithms, and demonstrate the approach by analyzing the two-dimensional quantum Ising model with transverse and parallel magnetic fields. PMID:18352611
Correspondence of I- and Q-balls as non-relativistic condensates
Mukaida, Kyohei; Takimoto, Masahiro E-mail: takimoto@hep-th.phys.s.u-tokyo.ac.jp
2014-08-01
If a real scalar field is dominated by non-relativistic modes, then it approximately conserves its particle number and obeys an equation that governs a complex scalar field theory with a conserved global U(1) symmetry. From this fact, it is shown that the I-ball (oscillon) can be naturally understood as a projection (e.g., real part) of the non-relativistic Q-ball solution. In particular, we clarify that the stability of the I-ball is guaranteed by the U(1) symmetry in the corresponding complex scalar field theory as long as the non-relativistic condition holds. We also discuss the longevity of I-ball from the perspective of the complex scalar field in terms of U(1) charge violating processes.
Light-Cone Distribution Amplitudes for Non-Relativistic Bound States
Feldmann, Th.; Bell, G.
2007-11-19
We calculate light-cone distribution amplitudes for non-relativistic bound states, including radiative corrections from relativistic gluon exchange to first order in the strong coupling constant. Our results apply to hard exclusive reactions with non-relativistic bound states in the QCD factorization approach like, for instance, B{sub c}{yields}{eta}{sub c}l{nu} or e{sup +}e{sup -}{yields}J/{psi}{eta}{sub c}. They also serve as a toy model for light-cone distribution amplitudes of light mesons or heavy B and D mesons.
Proteome Analysis of Ground State Pluripotency
Taleahmad, Sara; Mirzaei, Mehdi; Parker, Lindsay M.; Hassani, Seyedeh-Nafiseh; Mollamohammadi, Sepideh; Sharifi-Zarchi, Ali; Haynes, Paul A.; Baharvand, Hossein; Salekdeh, Ghasem Hosseini
2015-01-01
The differentiation potential of pluripotent embryonic stem cells (ESCs) can be manipulated via serum and medium conditions for direct cellular development or to maintain a naïve ground state. The self-renewal state of ESCs can thus be induced by adding inhibitors of mitogen activated protein kinase (MAPK) and glycogen synthase kinase-3 (Gsk3), known as 2 inhibitors (2i) treatment. We have used a shotgun proteomics approach to investigate differences in protein expressions between 2i- and serum-grown mESCs. The results indicated that 164 proteins were significantly upregulated and 107 proteins downregulated in 2i-grown cells compared to serum. Protein pathways in 2i-grown cells with the highest enrichment were associated with glycolysis and gluconeogenesis. Protein pathways related to organ development were downregulated in 2i-grown cells. In serum-grown ESCs, protein pathways involved in integrin and focal adhesion, and signaling proteins involved in the actin cytoskeleton regulation were enriched. We observed a number of nuclear proteins which were mostly involved in self-renewal maintenance and were expressed at higher levels in 2i compared to serum - Dnmt1, Map2k1, Parp1, Xpo4, Eif3g, Smarca4/Brg1 and Smarcc1/Baf155. Collectively, the results provided an insight into the key protein pathways used by ESCs in the ground state or metastable conditions through 2i or serum culture medium, respectively. PMID:26671762
Ground-state structures of Hafnium clusters
Ng, Wei Chun; Yoon, Tiem Leong; Lim, Thong Leng
2015-04-24
Hafnium (Hf) is a very large tetra-valence d-block element which is able to form relatively long covalent bond. Researchers are interested to search for substitution to silicon in the semi-conductor industry. We attempt to obtain the ground-state structures of small Hf clusters at both empirical and density-functional theory (DFT) levels. For calculations at the empirical level, charge-optimized many-body functional potential (COMB) is used. The lowest-energy structures are obtained via a novel global-minimum search algorithm known as parallel tempering Monte-Carlo Basin-Hopping and Genetic Algorithm (PTMBHGA). The virtue of using COMB potential for Hf cluster calculation lies in the fact that by including the charge optimization at the valence shells, we can encourage the formation of proper bond hybridization, and thus getting the correct bond order. The obtained structures are further optimized using DFT to ensure a close proximity to the ground-state.
B2N2O4: Prediction of a Magnetic Ground State for a Light Main-Group Molecule
Varga, Zoltan; Truhlar, Donald G.
2015-09-08
Cyclobutanetetrone, (CO)4, has a triplet ground state. Here we predict, based on electronic structure calculations, that the B2N2O4 molecule also has a triplet ground state and is therefore paramagnetic; the structure is an analogue of (CO)4 in which the carbon ring is replaced by a (BN)2 ring. Similar to (CO)4, the triplet ground-state structure of B2N2O4 is also thermodynamically unstable. Besides analysis of the molecular orbitals, we found that the partial atomic charges are good indicators for predicting magnetic ground states.
Ground state of the three-band Hubbard model
NASA Astrophysics Data System (ADS)
Yanagisawa, Takashi; Koike, Soh; Yamaji, Kunihiko
2001-11-01
The ground state of the two-dimensional three-band Hubbard model in oxide superconductors is investigated by using the variational Monte Carlo method. The Gutzwiller-projected BCS and spin density wave (SDW) functions are employed in the search for a possible ground state with respect to dependences on electron density. Antiferromagnetic correlations are considerably strong near half-filling. It is shown that the d-wave state may exist away from half-filling for both the hole and electron doping cases. The overall structure of the phase diagram obtained by our calculations qualitatively agrees with experimental indications. The superconducting condensation energy is in reasonable agreement with the experimental value obtained from specific heat and critical magnetic field measurements for optimally doped samples. The inhomogeneous SDW state is also examined near 1/8 doping. Incommensurate magnetic structures become stable due to hole doping in the underdoped region, where the transfer tpp between oxygen orbitals plays an important role in determining a stable stripe structure.
On the nature of the oligoacene ground state
NASA Astrophysics Data System (ADS)
Hachmann, Johannes; Dorando, Jonathan; Aviles, Michael; Kin-Lic Chan, Garnet
2007-03-01
The nature of the oligoacene ground state - its spin, singlet-triplet gap, and diradical character as a function of chain-length - is a question of ongoing theoretical and experimental interest with notable technological implications. Previous computational studies have given inconclusive answers to this challenging electronic structure problem (see e.g. [1]). In the present study we exploit the capabilities of the local ab initio Density Matrix Renormalization Group (DMRG) [2], which allows the numerically exact (FCI) solution of the Schr"odinger equation in a chosen 1-particle basis and active space for quasi-one-dimensional systems. We compute the singlet-triplet gap from first principles as a function of system length ranging from naphthalene to tetradecacene, correlating the full π-space (i.e. up to 58 electrons in 58 orbitals) and converging the results to a few μEh accuracy [3]. In order to study the diradical nature of the oligoacene ground state we calculate expectation values over different diradical occupation and pair-correlation operators. Furthermore we study the natural orbitals and their occupation. [1] Bendikov, Duong, Starkey, Houk, Carter, Wudl, JACS 126 (2004), 7416. [2] Hachmann, Cardoen, Chan, JCP 125 (2006), 144101. [3] Hachmann, Dorando, Avil'es, Chan, in preparation.
Continuous Optical Production of Ultracold Vibronic Ground State Polar Molecules
NASA Astrophysics Data System (ADS)
Bruzewicz, Colin David
We present recent results on the formation of ultracold polar molecules via photoassociation. Beginning with pre-cooled samples of Rb and Cs atoms, we produce electronically-excited molecules that inherit the ultracold temperature of their atomic precursors. In order to create large samples of ultracold molecules in their vibrational and rotational X 1Sigma+(upsilon=J=0) ground state, we study two different photoassociative regimes. In the first, molecules are created in a particular highly vibrationally-excited molecular state and decay strongly to a weakly-bound vibrational level in the ground a3Sigma + state. To study a possible population transfer scheme from this state to the X1Sigma+(upsilon=J=0) ground state, we present high-resolution depletion spectroscopy of the a 3Sigma+ c3Sigma+ transition for use in the first stage of a proposed Stimulated Raman Adiabatic Passage (STIRAP) transfer. In the second photoassociative regime, molecules are created in deeply-bound, electronically-excited vibrational levels that decay directly to the X1Sigma+(upsilon=0) state, obviating the need for population transfer. Through theoretical analysis and subsequent experimental verification, we demonstrate continuous formation of X 1Sigma+(upsilon=0) RbCs molecules at rates in excess of 103/s. We then conclude with detailed calculations of a method to purify the molecular sample of unwanted excited molecular states, based on inelastic scattering with ultracold Cs atoms.
NASA Astrophysics Data System (ADS)
Obukhov, A. E.
2012-06-01
The help of the measurements (the methods are the NMR 1H and 13C, infrared (IR) and the UV-absorption, Raman scattering of light, the fluorescence and the phosphorescence, the pumping of the lasers and lamps, the low-temperature of the spectroscopy in the solutions (77 K) and the Jet-spectroscopy of vapor (2,6 K) and others) and the calculations with application of the developed new complex of the computer of the programs realizing of the quantum-chemical LCAO-MO SCF extended-CI INDO / S of methods are investigated of the photophysical properties of some news and also some known the organic compounds for variations of the electronic and the spatial structures in the series is the mono-, bi-, three, penta- and quincli-cyclic and the bi- and the bis- phenyl, furyl- and tienyl- oxazoles and - oxadiazoles have been studied of the spectroscopy properties in the wavelength range max λ max abs,osc = 208 ÷ 760 nm.
All-Optical Scheme to Produce Quantum Degenerate Dipolar Molecules in the Vibronic Ground State
NASA Astrophysics Data System (ADS)
Mackie, Matt; Debrosse, Catherine
2010-03-01
We consider two-color heteronuclear photoassociation of Bose-condensed atoms into dipolar molecules in the J=1 vibronic ground state, where a free-ground laser couples atoms directly to the ground state and a free-bound laser couples the atoms to an electronically-excited state. The addition of the excited state creates a second pathway for creating ground state molecules, leading to quantum interference between direct photoassociation and photoassociation via the excited molecular state, as well as a dispersive-like shift of the free-ground resonance position. Using LiNa as an example, these results are shown to depend on the detuning and intensity of the free-bound laser, as well as the semi-classical size of both molecular states. Despite strong enhancement, coherent conversion to the LiNa vibronic ground state is possible only in a limited regime near the free-bound resonance.
Ziegler, Tom; Krykunov, Mykhaylo; Autschbach, Jochen
2014-09-01
The random phase approximation (RPA) equation of adiabatic time dependent density functional ground state response theory (ATDDFT) has been used extensively in studies of excited states. It extracts information about excited states from frequency dependent ground state response properties and avoids, thus, in an elegant way, direct Kohn-Sham calculations on excited states in accordance with the status of DFT as a ground state theory. Thus, excitation energies can be found as resonance poles of frequency dependent ground state polarizability from the eigenvalues of the RPA equation. ATDDFT is approximate in that it makes use of a frequency independent energy kernel derived from the ground state functional. It is shown in this study that one can derive the RPA equation of ATDDFT from a purely variational approach in which stationary states above the ground state are located using our constricted variational DFT (CV-DFT) method and the ground state functional. Thus, locating stationary states above the ground state due to one-electron excitations with a ground state functional is completely equivalent to solving the RPA equation of TDDFT employing the same functional. The present study is an extension of a previous work in which we demonstrated the equivalence between ATDDFT and CV-DFT within the Tamm-Dancoff approximation. PMID:26588541
Thermodynamic ground states of platinum metal nitrides
Aberg, D; Sadigh, B; Crowhurst, J; Goncharov, A
2007-10-09
We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.
Probing the ground state in gauge theories
Heinzl, T.; Ilderton, A.; Langfeld, K.; Lavelle, M.; McMullan, D.; Lutz, W.
2008-03-01
We consider two very different models of the flux tube linking two heavy quarks: a string linking the matter fields and a Coulombic description of two separately gauge invariant charges. We compare how close they are to the unknown true ground state in compact U(1) and the SU(2) Higgs model. Simulations in compact U(1) show that the string description is better in the confined phase but the Coulombic description is best in the deconfined phase; the last result is shown to agree with analytical calculations. Surprisingly in the nonabelian theory the Coulombic description is better in both the Higgs and confined phases. This indicates a significant difference in the width of the flux tubes in the two theories.
Ground state of high-density matter
NASA Technical Reports Server (NTRS)
Copeland, ED; Kolb, Edward W.; Lee, Kimyeong
1988-01-01
It is shown that if an upper bound to the false vacuum energy of the electroweak Higgs potential is satisfied, the true ground state of high-density matter is not nuclear matter, or even strange-quark matter, but rather a non-topological soliton where the electroweak symmetry is exact and the fermions are massless. This possibility is examined in the standard SU(3) sub C tensor product SU(2) sub L tensor product U(1) sub Y model. The bound to the false vacuum energy is satisfied only for a narrow range of the Higgs boson masses in the minimal electroweak model (within about 10 eV of its minimum allowed value of 6.6 GeV) and a somewhat wider range for electroweak models with a non-minimal Higgs sector.
Ground states of finite spherical Yukawa crystals
NASA Astrophysics Data System (ADS)
Baumgartner, H.; Asmus, D.; Golubnychiy, V.; Ludwig, P.; Kählert, H.; Bonitz, M.
2008-09-01
Small three-dimensional strongly coupled clusters of charged particles in a spherical confinement potential arrange themselves in nested concentric shells. If the particles are immersed into a background plasma the interaction is screened. The cluster shell configuration is known to be sensitive to the screening strength. With increased screening, an increased population of the inner shell(s) is observed. Here, we present a detailed analysis of the ground state shell configurations and configuration changes in a wide range of screening parameters for clusters with particle numbers N in the range of 11 to 60. We report three types of anomalous behaviors which are observed upon increase of screening, at fixed N or for an increase of N at fixed screening. The results are obtained by means of extensive first principle molecular dynamics simulations.
Essentially exact ground-state calculations by superpositions of nonorthogonal Slater determinants
NASA Astrophysics Data System (ADS)
Goto, Hidekazu; Kojo, Masashi; Sasaki, Akira; Hirose, Kikuji
2013-05-01
An essentially exact ground-state calculation algorithm for few-electron systems based on superposition of nonorthogonal Slater determinants (SDs) is described, and its convergence properties to ground states are examined. A linear combination of SDs is adopted as many-electron wave functions, and all one-electron wave functions are updated by employing linearly independent multiple correction vectors on the basis of the variational principle. The improvement of the convergence performance to the ground state given by the multi-direction search is shown through comparisons with the conventional steepest descent method. The accuracy and applicability of the proposed scheme are also demonstrated by calculations of the potential energy curves of few-electron molecular systems, compared with the conventional quantum chemistry calculation techniques.
The Non-Relativistic Limit for the e-MHD Equations
Zhao, Jie
2014-01-01
We investigate the non-relativistic limit for the e-MHD equations in a three-dimension unit periodic torus. With the prepared initial data, our result shows that the small parameter problems have unique solutions existing in the finite time interval where the corresponding limit problems (incompressible Euler equations) have smooth solutions. Moreover, the formal limit is rigorously justified. PMID:24672303
Simulations of ion acceleration at non-relativistic shocks. I. Acceleration efficiency
Caprioli, D.; Spitkovsky, A.
2014-03-10
We use two-dimensional and three-dimensional hybrid (kinetic ions-fluid electrons) simulations to investigate particle acceleration and magnetic field amplification at non-relativistic astrophysical shocks. We show that diffusive shock acceleration operates for quasi-parallel configurations (i.e., when the background magnetic field is almost aligned with the shock normal) and, for large sonic and Alfvénic Mach numbers, produces universal power-law spectra ∝p {sup –4}, where p is the particle momentum. The maximum energy of accelerated ions increases with time, and it is only limited by finite box size and run time. Acceleration is mainly efficient for parallel and quasi-parallel strong shocks, where 10%-20% of the bulk kinetic energy can be converted to energetic particles and becomes ineffective for quasi-perpendicular shocks. Also, the generation of magnetic turbulence correlates with efficient ion acceleration and vanishes for quasi-perpendicular configurations. At very oblique shocks, ions can be accelerated via shock drift acceleration, but they only gain a factor of a few in momentum and their maximum energy does not increase with time. These findings are consistent with the degree of polarization and the morphology of the radio and X-ray synchrotron emission observed, for instance, in the remnant of SN 1006. We also discuss the transition from thermal to non-thermal particles in the ion spectrum (supra-thermal region) and we identify two dynamical signatures peculiar of efficient particle acceleration, namely, the formation of an upstream precursor and the alteration of standard shock jump conditions.
NASA Astrophysics Data System (ADS)
Long, Andrew J.; Lunardini, Cecilia; Sabancilar, Eray
2014-08-01
We study the physics potential of the detection of the Cosmic Neutrino Background via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of Δ ~ 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m1 simeq m2 simeq m3 = mν gtrsim 0.1 eV. These neutrinos are non-relativistic today; detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2 mν above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is Δ lesssim 0.7 mν . Interestingly, the total capture rate depends on the origin of the neutrino mass, being ΓD simeq 4 and ΓM simeq 8 events per year (for a 100 g tritium target) for unclustered Dirac and Majorana neutrinos, respectively. An enhancement of the rate of up to Script O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Turning to more exotic neutrino physics, PTOLEMY could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. The experiment would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.
Long, Andrew J.; Lunardini, Cecilia; Sabancilar, Eray E-mail: Cecilia.Lunardini@asu.edu
2014-08-01
We study the physics potential of the detection of the Cosmic Neutrino Background via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of Δ ∼ 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m{sub 1} ≅ m{sub 2} ≅ m{sub 3} = m{sub ν} ∼> 0.1 eV. These neutrinos are non-relativistic today; detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2 m{sub ν} above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is Δ ∼< 0.7 m{sub ν} . Interestingly, the total capture rate depends on the origin of the neutrino mass, being Γ{sup D} ≅ 4 and Γ{sup M} ≅ 8 events per year (for a 100 g tritium target) for unclustered Dirac and Majorana neutrinos, respectively. An enhancement of the rate of up to O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Turning to more exotic neutrino physics, PTOLEMY could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. The experiment would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.
Tuning the Ground State Symmetry of Acetylenyl Radicals.
Zeng, Tao; Danovich, David; Shaik, Sason; Ananth, Nandini; Hoffmann, Roald
2015-08-26
The lowest excited state of the acetylenyl radical, HCC, is a (2)Π state, only 0.46 eV above the ground state, (2)Σ(+). The promotion of an electron from a π bond pair to a singly occupied σ hybrid orbital is all that is involved, and so we set out to tune those orbital energies, and with them the relative energetics of (2)Π and (2)Σ(+) states. A strategy of varying ligand electronegativity, employed in a previous study on substituted carbynes, RC, was useful, but proved more difficult to apply for substituted acetylenyl radicals, RCC. However, π-donor/acceptor substitution is effective in modifying the state energies. We are able to design molecules with (2)Π ground states (NaOCC, H2NCC ((2)A″), HCSi, FCSi, etc.) and vary the (2)Σ(+)-(2)Π energy gap over a 4 eV range. We find an inconsistency between bond order and bond dissociation energy measures of the bond strength in the Si-containing molecules; we provide an explanation through an analysis of the relevant potential energy curves. PMID:27162981
Tuning the Ground State Symmetry of Acetylenyl Radicals
2015-01-01
The lowest excited state of the acetylenyl radical, HCC, is a 2Π state, only 0.46 eV above the ground state, 2Σ+. The promotion of an electron from a π bond pair to a singly occupied σ hybrid orbital is all that is involved, and so we set out to tune those orbital energies, and with them the relative energetics of 2Π and 2Σ+ states. A strategy of varying ligand electronegativity, employed in a previous study on substituted carbynes, RC, was useful, but proved more difficult to apply for substituted acetylenyl radicals, RCC. However, π-donor/acceptor substitution is effective in modifying the state energies. We are able to design molecules with 2Π ground states (NaOCC, H2NCC (2A″), HCSi, FCSi, etc.) and vary the 2Σ+–2Π energy gap over a 4 eV range. We find an inconsistency between bond order and bond dissociation energy measures of the bond strength in the Si-containing molecules; we provide an explanation through an analysis of the relevant potential energy curves. PMID:27162981
Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun
2016-01-01
Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986
Magnetic ground state of FeSe.
Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K; Iida, K; Christianson, A D; Walker, H C; Adroja, D T; Abdel-Hafiez, M; Chen, Xiaojia; Chareev, D A; Vasiliev, A N; Zhao, Jun
2016-01-01
Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ∼60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities. PMID:27431986
Strangeness in the baryon ground states
NASA Astrophysics Data System (ADS)
Semke, A.; Lutz, M. F. M.
2012-10-01
We compute the strangeness content of the baryon octet and decuplet states based on an analysis of recent lattice simulations of the BMW, PACS, LHPC and HSC groups for the pion-mass dependence of the baryon masses. Our results rely on the relativistic chiral Lagrangian and large-Nc sum rule estimates of the counter terms relevant for the baryon masses at N3LO. A partial summation is implied by the use of physical baryon and meson masses in the one-loop contributions to the baryon self energies. A simultaneous description of the lattice results of the BMW, LHPC, PACS and HSC groups is achieved. From a global fit we determine the axial coupling constants F ≃ 0.45 and D ≃ 0.80 in agreement with their values extracted from semi-leptonic decays of the baryons. Moreover, various flavor symmetric limits of baron octet and decuplet masses as obtained by the QCDSF-UKQCD group are recovered. We predict the pion- and strangeness sigma terms and the pion-mass dependence of the octet and decuplet ground states at different strange quark masses.
NASA Astrophysics Data System (ADS)
Wang, Qisi; Shen, Yao; Pan, Bingying; Zhang, Xiaowen; Ikeuchi, K.; Iida, K.; Christianson, A. D.; Walker, H. C.; Adroja, D. T.; Abdel-Hafiez, M.; Chen, Xiaojia; Chareev, D. A.; Vasiliev, A. N.; Zhao, Jun
2016-07-01
Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, and its magnetic ground state is intensely debated. Here we report inelastic neutron-scattering experiments that reveal both stripe and Néel spin fluctuations over a wide energy range at 110 K. On entering the nematic phase, a substantial amount of spectral weight is transferred from the Néel to the stripe spin fluctuations. Moreover, the total fluctuating magnetic moment of FeSe is ~60% larger than that in the iron pnictide BaFe2As2. Our results suggest that FeSe is a novel S=1 nematic quantum-disordered paramagnet interpolating between the Néel and stripe magnetic instabilities.
Neutrino ground state in a dense star
NASA Astrophysics Data System (ADS)
Kiers, Ken; Tytgat, Michel H. G.
1998-05-01
It has recently been argued that long range forces due to the exchange of massless neutrinos give rise to a very large self-energy in a dense, finite-ranged, weakly charged medium. Such an effect, if real, would destabilize a neutron star. To address this issue we have studied the related problem of a massless neutrino field in the presence of an external, static electroweak potential of finite range. To be precise, we have computed to one loop the exact vacuum energy for the case of a spherical square well potential of depth α and radius R. For small wells, the vacuum energy is reliably determined by a perturbative expansion in the external potential. For large wells, however, the perturbative expansion breaks down. A manifestation of this breakdown is that the vacuum carries a non-zero neutrino charge. The energy and neutrino charge of the ground state are, to a good approximation for large wells, those of a neutrino condensate with chemical potential μ=α. Our results demonstrate explicitly that long-range forces due to the exchange of massless neutrinos do not threaten the stability of neutron stars.
Ground state energy of N Frenkel excitons
NASA Astrophysics Data System (ADS)
Pogosov, W.; Combescot, M.
2009-03-01
By using the composite many-body theory for Frenkel excitons we have recently developed, we here derive the ground state energy of N Frenkel excitons in the Born approximation through the Hamiltonian mean value in a state made of N identical Q = 0 excitons. While this quantity reads as a density expansion in the case of Wannier excitons, due to many-body effects induced by fermion exchanges between N composite particles, we show that the Hamiltonian mean value for N Frenkel excitons only contains a first order term in density, just as for elementary bosons. Such a simple result comes from a subtle balance, difficult to guess a priori, between fermion exchanges for two or more Frenkel excitons appearing in Coulomb term and the ones appearing in the N exciton normalization factor - the cancellation being exact within terms in 1/Ns where Ns is the number of atomic sites in the sample. This result could make us naively believe that, due to the tight binding approximation on which Frenkel excitons are based, these excitons are just bare elementary bosons while their composite nature definitely appears at various stages in the precise calculation of the Hamiltonian mean value.
Ground state of naphthyl cation: Singlet or triplet?
Dutta, Achintya Kumar; Vaval, Nayana Pal, Sourav; Manohar, Prashant U.
2014-03-21
We present a benchmark theoretical investigation on the electronic structure and singlet-triplet(S-T) gap of 1- and 2-naphthyl cations using the CCSD(T) method. Our calculations reveal that the ground states of both the naphthyl cations are singlet, contrary to the results obtained by DFT/B3LYP calculations reported in previous theoretical studies. However, the triplet states obtained in the two structural isomers of naphthyl cation are completely different. The triplet state in 1-naphthyl cation is (π,σ) type, whereas in 2-naphthyl cation it is (σ,σ{sup ′}) type. The S-T gaps in naphthyl cations and the relative stability ordering of the singlet and the triplet states are highly sensitive to the basis-set quality as well as level of correlation, and demand for inclusion of perturbative triples in the coupled-cluster ansatz.
Ground-state properties of a triangular triple quantum dot connected to superconducting leads
NASA Astrophysics Data System (ADS)
Oguri, Akira; Sato, Izumi; Shimamoto, Masashi; Tanaka, Yoichi
2015-03-01
We study ground-state properties of a triangular triple quantum dot connected to two superconducting (SC) leads. In this system orbital motion along the triangular configuration causes various types of quantum phases, such as the SU(4) Kondo state and the Nagaoka ferromagnetic mechanism, depending on the electron filling. The ground state also evolves as the Cooper pairs penetrate from the SC leads. We describe the phase diagram in a wide range of the parameter space, varying the gate voltage, the couplings between the dots and leads, and also the Josephson phase between the SC gaps. The results are obtained in the limit of large SC gap, carrying out exact diagonalization of an effective Hamiltonian. We also discuss in detail a classification of the quantum states according to the fixed point of the Wilson numerical renormalization group (NRG). Furthermore, we show that the Bogoliubov zero-energy excitation determines the ground state of a π Josephson junction at small electron fillings.
Cavity loss factors of non-relativistic beams for Project X
Lunin, A.; Yakovlev, V.; Kazakov, S.; /Fermilab
2011-03-01
Cavity loss factor calculation is an important part of the total cryolosses estimation for the super conductive (SC) accelerating structures. There are two approaches how to calculate cavity loss factors, the integration of a wake potential over the bunch profile and the addition of loss factors for individual cavity modes. We applied both methods in order to get reliable results for non-relativistic beam. The time domain CST solver was used for a wake potential calculation and the frequency domain HFSS code was used for the cavity eigenmodes spectrum findings. Finally we present the results of cavity loss factors simulations for a non-relativistic part of the ProjectX and analyze it for various beam parameters.
Ground-state energetics of helium and deuterium fermion fluids
NASA Astrophysics Data System (ADS)
Krotscheck, E.; Smith, R. A.; Clark, J. W.; Panoff, R. M.
1981-12-01
description of the ground-state energetics of liquid 3He. Bulk atomic deuterium with all electronic spins aligned is treated at the same level of approximation as applied to helium. Three choices of nuclear-spin distribution are examined, with a single spin state present, or two or three equally populated nuclear spin states. The finite-density energy minimum is found to lie very close to zero energy in all three examples; a very precise many-body calculation will thus be needed to decide their liquid or gaseous nature at zero temperature under zero external pressure.
Condensation for non-relativistic matter in Hořava-Lifshitz gravity
NASA Astrophysics Data System (ADS)
Jing, Jiliang; Chen, Songbai; Pan, Qiyuan
2015-10-01
We study condensation for non-relativistic matter in a Hořava-Lifshitz black hole without the condition of the detailed balance. We show that, for the fixed non-relativistic parameter α2 (or the detailed balance parameter ɛ), it is easier for the scalar hair to form as the parameter ɛ (or α2) becomes larger, but the condensation is not affected by the non-relativistic parameter β2. We also find that the ratio of the gap frequency in conductivity to the critical temperature decreases with the increase of ɛ and α2, but increases with the increase of β2. The ratio can reduce to the Horowitz-Roberts relation ωg /Tc ≈ 8 obtained in the Einstein gravity and Cai's result ωg /Tc ≈ 13 found in a Hořava-Lifshitz gravity with the condition of the detailed balance for the relativistic matter. Especially, we note that the ratio can arrive at the value of the BCS theory ωg /Tc ≈ 3.5 by taking proper values of the parameters.
Interface Representations of Critical Ground States
NASA Astrophysics Data System (ADS)
Kondev, Jane
1995-01-01
We study the critical properties of the F model, the three-coloring model on the honeycomb lattice, and the four-coloring model on the square lattice, by mapping these models to models of rough interfaces. In particular, we construct operators in a systematic way, which is provided by the interface representation, and we show that their scaling dimensions can be related to the stiffness of the interface. Two types of operators are found, and they correspond to electric and magnetic charges in the Coulomb gas which is related to the interface model by the usual duality transformation. Furthermore, we find that the stiffness of the interface models, and therefore all the critical exponents, can be calculated exactly by considering the contour correlation function which measures the probability that two points on the interface belong to the same contour loop. The exact information about the stiffness also allows us to analyze in detail the conformal field theories (CFT) that represent the scaling limits of the interface models. We find that CFT's associated with the F model, the three -coloring model, and the four-coloring model, have chiral symmetry algebras given by the su(2)_{k=1 }, su(3)_{k=1}, and su(4) _{k=1} Kac-Moody algebras, respectively. The three-coloring and the four coloring-model are ground states of certain antiferromagnetic Potts models, and the behavior of these Potts models at small but finite temperatures is determined by topological defects that can be defined in the associated interface models. In this way we calculate the correlation length and the specific heat of the Potts models, and they are in good agreement with numerical simulations. We also present our Monte-Carlo results for the scaling dimensions of operators in the four-coloring model, and they are in excellent agreement with our analytical results. Finally, we define geometrical exponents for contour loops on self -affine interfaces and calculate their values as a function of the
Triaxiality of the ground states in the 174W
NASA Astrophysics Data System (ADS)
Ya, Tu; Chen, Y. S.; Liu, L.; Gao, Z. C.
2016-05-01
We have performed calculations for the ground states in 174W by using the projected total energy surface (PTES) calculations. Both the ground state (g.s.) band and its γ band reproduce the experimental data. Further discussion about the triaxiality in 174W has been made by transition quardrupole moment (Qt) and comparing between the PTES and TRS methods.
Towards Chemically Stable Fermionic Ground State Molecules with Strong Dipolar Interactions
NASA Astrophysics Data System (ADS)
Will, Sebastian; Park, Jee; Wu, Cheng-Hsun; Schloss, Jennifer; Zwierlein, Martin
2013-05-01
Quantum gases with dipolar interactions will open new avenues for the creation of novel quantum many-body systems with intriguing properties, ranging from crystalline over magnetic to topological phases. A promising route for the experimental realization of dipolar quantum gases is the formation of fermionic ground-state molecules with a large electric dipole moment, giving rise to long-range anisotropic interactions. With our experiment we work towards the realization of fermionic ground state molecules of 23Na40K. The NaK ground state molecule is chemically stable and possesses a large induced electric dipole moment of 2.72 Debye. In pioneering studies, we have created nearly degenerate samples of weakly bound 23Na40K Feshbach molecules. With a long lifetime and a significant admixture of the electronic spin singlet state, the Feshbach molecules are an ideal starting point to reach the singlet rovibrational ground state with a two-photon STIRAP transfer. Aiming for an efficient transfer path, we have performed spectroscopic studies on excited and ground state molecular potentials of 23Na40K and will report on our current progress. This work was supported by the NSF, AFOSR-MURI and -PECASE, ARO-MURI, ONR YIP, DARPA YFA, a grant from the Army Research Office with funding from the DARPA OLE program and the David and Lucille Packard Foundation.
Creation of an Ultracold Gas of Ground-State Dipolar 23Na 87 Molecules
NASA Astrophysics Data System (ADS)
Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier; Wang, Dajun
2016-05-01
We report the successful production of an ultracold sample of absolute ground-state 23Na 87Rb molecules. Starting from weakly bound Feshbach molecules formed via magnetoassociation, the lowest rovibrational and hyperfine level of the electronic ground state is populated following a high-efficiency and high-resolution two-photon Raman process. The high-purity absolute ground-state samples have up to 8000 molecules and densities of over 1011 cm-3 . By measuring the Stark shifts induced by external electric fields, we determined the permanent electric dipole moment of the absolute ground-state 23Na 87Rb and demonstrated the capability of inducing an effective dipole moment over 1 D. Bimolecular reaction between ground-state 23Na 87Rb molecules is endothermic, but we still observed a rather fast decay of the molecular sample. Our results pave the way toward investigation of ultracold molecular collisions in a fully controlled manner and possibly to quantum gases of ultracold bosonic molecules with strong dipolar interactions.
Is the ground state of Yang-Mills theory Coulombic?
Heinzl, T.; Ilderton, A.; Langfeld, K.; Lavelle, M.; McMullan, D.; Lutz, W.
2008-08-01
We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-Abelian Coulomb fields is found to have a good overlap with the ground state for all charge separations. In fact, the overlap increases as the lattice regulator is removed. This opens up the possibility that the Coulomb state is the true ground state in the continuum limit.
Ground State Properties of the 1/2 Flux Harper Hamiltonian
NASA Astrophysics Data System (ADS)
Kennedy, Colin; Burton, William Cody; Chung, Woo Chang; Ketterle, Wolfgang
2015-05-01
The Harper Hamiltonian describes the motion of charged particles in an applied magnetic field - the spectrum of which exhibits the famed Hofstadter's butterfly. Recent advances in driven optical lattices have made great strides in simulating nontrivial Hamiltonians, such as the Harper model, in the time-averaged sense. We report on the realization of the ground state of bosons in the Harper Hamiltonian for 1/2 flux per plaquette utilizing a tilted two-dimensional lattice with laser assisted tunneling. We detail progress in studying various ground state properties of the 1/2 flux Harper Hamiltonian including ground state degeneracies, gauge-dependent observables, effects of micromotion, adiabatic loading schemes, and emergence and decay of coherence. Additionally, we describe prospects for flux rectification using a period-tripled superlattice and generalizations to three dimensions. MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, Department of Physics, Massachusetts Institute of Technology.
A MRSDCI characterization of the ground state of CaC
NASA Astrophysics Data System (ADS)
Takada, Hellinton H.; Pelegrini, Marina; Roberto-Neto, Orlando; Machado, Francisco B. C.
2002-09-01
Accurate potential energy curves, dipole moment functions, dissociation energies and spectroscopic constants for six electronic states ( 3Σ-, 3Π, 5Σ-, 1Δ, 1Π, 1Σ+) of the CaC molecule are reported with the multireference singles and doubles configuration interaction methodology. The ground state has symmetry 3Σ -, with a dissociation energy ( D0) equal to 1.94 eV. The 5Σ - state is the first excited state lying 695 cm-1 above the 3Σ - ground state. The 1Δ and 3Π states are the second and third excited states separated, respectively, by 10 763 and 12 167 cm-1 from the 3Σ - ground state.
Dissociative recombination of the ground state of N2(+)
NASA Technical Reports Server (NTRS)
Guberman, Steven L.
1991-01-01
Large-scale calculations of the dissociative recombination cross sections and rates for the v = 0 level of the N2(+) ground state are reported, and the important role played by vibrationally excited Rydberg states lying both below and above the v = 0 level of the ion is demonstrated. The large-scale electronic wave function calculations were done using triple zeta plus polarization nuclear-centered-valence Gaussian basis sets. The electronic widths were obtained using smaller wave functions, and the cross sections were calculated on the basis of the multichannel quantum defect theory. The DR rate is calculated at 1.6 x 10 to the -7th x (Te/300) to the -0.37 cu cm/sec for Te in the range of 100 to 1000 K, and is found to be in excellent agreement with prior microwave afterglow experiments but in disagreement with recent merged beam results. It is inferred that the dominant mechanism for DR imparts sufficient energy to the product atoms to allow for escape from the Martian atmosphere.
NASA Astrophysics Data System (ADS)
Liu, Jia; Xiao, Jing-Ling
2006-10-01
We study theoretically the ground state energy of a polaron near the interface of a polar-polar semiconductor by considering the Rashba spin-orbit (SO) coupling with the Lee-Low-Pines intermediate coupling method. Our numerical results show that the Rashba SO interaction originating from the inversion asymmetry in the heterostructure splits the ground state energy of the polaron. The electron areal density and vector dependence of the ratio of the SO interaction to the total ground state energy or other energy composition are obvious. One can see that even without any external magnetic field, the ground state energy can be split by the Rashba SO interaction, and this split is not a single but a complex one. Since the presents of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the polaron are more stable than electron's.
Ground states of stealthy hyperuniform potentials: I. Entropically favored configurations
NASA Astrophysics Data System (ADS)
Zhang, G.; Stillinger, F. H.; Torquato, S.
2015-08-01
Systems of particles interacting with "stealthy" pair potentials have been shown to possess infinitely degenerate disordered hyperuniform classical ground states with novel physical properties. Previous attempts to sample the infinitely degenerate ground states used energy minimization techniques, introducing algorithmic dependence that is artificial in nature. Recently, an ensemble theory of stealthy hyperuniform ground states was formulated to predict the structure and thermodynamics that was shown to be in excellent agreement with corresponding computer simulation results in the canonical ensemble (in the zero-temperature limit). In this paper, we provide details and justifications of the simulation procedure, which involves performing molecular dynamics simulations at sufficiently low temperatures and minimizing the energy of the snapshots for both the high-density disordered regime, where the theory applies, as well as lower densities. We also use numerical simulations to extend our study to the lower-density regime. We report results for the pair correlation functions, structure factors, and Voronoi cell statistics. In the high-density regime, we verify the theoretical ansatz that stealthy disordered ground states behave like "pseudo" disordered equilibrium hard-sphere systems in Fourier space. The pair statistics obey certain exact integral conditions with very high accuracy. These results show that as the density decreases from the high-density limit, the disordered ground states in the canonical ensemble are characterized by an increasing degree of short-range order and eventually the system undergoes a phase transition to crystalline ground states. In the crystalline regime (low densities), there exist aperiodic structures that are part of the ground-state manifold but yet are not entropically favored. We also provide numerical evidence suggesting that different forms of stealthy pair potentials produce the same ground-state ensemble in the zero
NASA Astrophysics Data System (ADS)
Musiał, Monika; Bartlett, Rodney J.
2007-07-01
New iterative double and triple excitation corrections to the equation-of-motion coupled cluster (EOM-CC) based upon the recently developed nCC methods [Bartlett and Musiał, J. Chem. Phys. 125, 204105-1 (2006)] are applied to excitation energies (EEs), ionization potentials (IPs), and electron affinities (EAs). The methods have been tested by the evaluation of the vertical EEs, IPs, and EAs for Ne, BH, CH2, H2O, N2, C2, CH+, CO, and C2H4 compared to full configuration interaction, EOM-CCSD, EOM-CCSDT, and experimental data.
Sun, Z.; Douglas, J. F.; Wang, Q.; Dessau, D. S.; Fedorov, A. V.; Lin, H.; Sahrakorpi, S.; Barbiellini, B.; Markiewicz, R. S.; Bansil, A.; Zheng, H.; Mitchell, J. F.; Materials Science Division; Univ. of Colorado; LBNL; Northeastern Univ.
2008-01-01
Using angle-resolved photoemission spectroscopy, we present the electronic structure of the metallic ground state of La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x {approx} 0.59) and interpret the results in terms of first-principles band-structure computations, of which the generalized gradient approximation yields the best agreement with the experimental data. No bilayer-split bands are found in this compound, indicating the near degeneracy of electronic states in the neighboring MnO{sub 2} layers due to its A-type antiferromagnetic structure. The d{sub 3z{sup 2}-r{sup 2}} states near the zone center were not observed, which is also consistent with its A-type antiferromagnetic structure. Near the Fermi level, a kink in the dispersion reveals an important electron-phonon many-body interaction. The electron-phonon coupling is {approx}1 near the zone boundary and {approx}2 near the zone diagonal, showing strong k dependence.
NASA Astrophysics Data System (ADS)
De, Sanchari; Ghosh, Sutapa; Chakrabarty, Somenath
2015-11-01
In the conventional scenario, the Hawking radiation is believed to be a tunneling process at the event horizon of the black hole. In the quantum field theoretic approach the Schwinger's mechanism is generally used to give an explanation of this tunneling process. It is the decay of quantum vacuum into particle anti-particle pairs near the black hole surface. However, in a reference frame undergoing a uniform accelerated motion in an otherwise flat Minkowski space-time geometry, in the non-relativistic approximation, the particle production near the event horizon of a black hole may be treated as a kind of Fowler-Nordheim field emission, which is the typical electron emission process from a metal surface under the action of an external electrostatic field. This type of emission from metal surface is allowed even at extremely low temperature. It has been noticed that in one-dimensional scenario, the Schrödinger equation satisfied by the created particle (anti-particle) near the event horizon, can be reduced to a differential form which is exactly identical with that obeyed by an electron immediately after the emission from the metal surface under the action of a strong electrostatic field. The mechanism of particle production near the event horizon of a black hole is therefore identified with Schwinger process in relativistic quantum field theory, whereas in the non-relativistic scenario it may be interpreted as Fowler-Nordheim emission process, when observed from a uniformly accelerated frame.
The ground-state average structure of methyl isocyanide
NASA Astrophysics Data System (ADS)
Mackenzie, M. W.; Duncan, J. L.
The use of recently determined highly precise inertial data for various isotopic modifications of methyl isocyanide has enabled the ground-state average, or rz, structure to be determined to within very narrow limits. Harmonic corrections to ground-state rotational constants have been calculated using a high-quality, experimentally determined harmonic force field. The derived zero-point inertial constants are sufficiently accurate to enable changes in the CH bond length and NCH bond angle on deuteration to be determined. The present rz structure determination is believed to be a physically realistic estimate of the ground-state average geometry of methyl isocyanide.
The ground-state average structure of methyl isocyanide
NASA Astrophysics Data System (ADS)
Mackenzie, M. W.; Duncan, J. L.
1982-11-01
The use of recently determined highly precise inertial data for various isotopic modifications of methyl isocyanide has enabled the ground-state average, or rz, structure to be determined to within very narrow limits. Harmonic corrections to ground-state rotational constants have been calculated using a high-quality, experimentally determined harmonic force field. The derived zero-point inertial constants are sufficiently accurate to enable changes in the CH bond length and NCH bond angle on deuteration to be determined. The present rz structure determination is believed to be a physically realistic estimate of the ground-state average geometry of methyl isocyanide.
Analysis of ground state in random bipartite matching
NASA Astrophysics Data System (ADS)
Shi, Gui-Yuan; Kong, Yi-Xiu; Liao, Hao; Zhang, Yi-Cheng
2016-02-01
Bipartite matching problems emerge in many human social phenomena. In this paper, we study the ground state of the Gale-Shapley model, which is the most popular bipartite matching model. We apply the Kuhn-Munkres algorithm to compute the numerical ground state of the model. For the first time, we obtain the number of blocking pairs which is a measure of the system instability. We also show that the number of blocking pairs formed by each person follows a geometric distribution. Furthermore, we study how the connectivity in the bipartite matching problems influences the instability of the ground state.
NASA Astrophysics Data System (ADS)
Pennisi, S.; Carrisi, M. C.; Scanu, A.
2006-03-01
It is well known that, in the relativistic context the relativity principle isn't imposed by separating variables into convective and non convective parts, but by imposing that the costitutive functions satisfy particular conditions; likely to this, the present considerations show that the same results are obtained also in the classical context. The result is achieved by taking the non-relativistic limit of Einstein's Relativity Principle. This fact furnishes further arguments on the naturalness of the work “A new method to exploit the Entropy Principle and Galilean invariance in the macroscopic approach of Extended Thermodynamics” by Pennisi and Ruggeri.
Approximating the ground state of gapped quantum spin systems
Michalakis, Spyridon; Hamza, Eman; Nachtergaele, Bruno; Sims, Robert
2009-01-01
We consider quantum spin systems defined on finite sets V equipped with a metric. In typical examples, V is a large, but finite subset of Z{sup d}. For finite range Hamiltonians with uniformly bounded interaction terms and a unique, gapped ground state, we demonstrate a locality property of the corresponding ground state projector. In such systems, this ground state projector can be approximated by the product of observables with quantifiable supports. In fact, given any subset {chi} {contained_in} V the ground state projector can be approximated by the product of two projections, one supported on {chi} and one supported on {chi}{sup c}, and a bounded observable supported on a boundary region in such a way that as the boundary region increases, the approximation becomes better. Such an approximation was useful in proving an area law in one dimension, and this result corresponds to a multi-dimensional analogue.
Possible ground-state octupole deformation in /sup 229/Pa
Ahmad, I.; Gindler, J.E.; Betts, R.R.; Chasman, R.R.; Friedman, A.M.
1982-12-13
Evidence is presented for the occurrence of a (5/2)/sup + -/ parity doublet as the ground state of /sup 229/Pa, in agreement with a previous theoretical prediction. The doublet splitting energy is measured to be 0.22 +- 0.05 keV. The relation of this doublet to ground-state octupole deformation is discussed. .ID LV2109 .PG 1762 1764
Theory of ground state factorization in quantum cooperative systems.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2008-05-16
We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range. PMID:18518481
Ground states of baryoleptonic Q-balls in supersymmetric models
Shoemaker, Ian M.; Kusenko, Alexander
2008-10-01
In supersymmetric generalizations of the standard model, all stable Q-balls are associated with some flat directions. We show that, if the flat direction has both the baryon number and the lepton number, the scalar field inside the Q-ball can deviate slightly from the flat direction in the ground state. We identify the true ground states of such nontopological solitons, including the electrically neutral and electrically charged Q-balls.
Antiferromagnetic ground state in NpCoGe
NASA Astrophysics Data System (ADS)
Colineau, E.; Griveau, J.-C.; Eloirdi, R.; Gaczyński, P.; Khmelevskyi, S.; Shick, A. B.; Caciuffo, R.
2014-03-01
NpCoGe, the neptunium analog of the ferromagnetic superconductor UCoGe, has been investigated by dc magnetization, ac susceptibility, specific heat, electrical resistivity, Hall effect, 237Np Mössbauer spectroscopy, and local spin-density approximation (LSDA) calculations. NpCoGe exhibits an antiferromagnetic ground state with a Néel temperature TN≈13 K and an average ordered magnetic moment <μNp>=0.80μB. The magnetic phase diagram has been determined and shows that the antiferromagnetic structure is destroyed by the application of a magnetic field (≈3 T). The value of the isomer shift suggests a Np3+ charge state (configuration 5f4). A high Sommerfeld coefficient value for NpCoGe (170 mJ mol-1 K-2) is inferred from specific heat. LSDA calculations indicate strong magnetic anisotropy and easy magnetization along the c axis. Mössbauer data and calculated exchange interactions support the possible occurrence of an elliptical spin-spiral structure in NpCoGe. The comparison with NpRhGe and uranium analogs suggests the leading role of 5f-d hybridization, the rather delocalized character of 5f electrons in NpCoGe, and the possible proximity of NpRuGe or NpFeGe to a magnetic quantum critical point.
Continuous Vibrational Cooling of Ground State Rb2
NASA Astrophysics Data System (ADS)
Tallant, Jonathan; Marcassa, Luis
2014-05-01
The process of photoassociation generally results in a distribution of vibrational levels in the electronic ground state that is energetically close to the dissociation limit. Several schemes have appeared that aim to transfer the population from the higher vibrational levels to lower ones, especially the ground vibrational state. We demonstrate continuous production of vibrationally cooled Rb2 using optical pumping. The vibrationally cooled molecules are produced in three steps. First, we use a dedicated photoassociation laser to produce molecules in high vibrational levels of the X1Σg+ state. Second, a broadband fiber laser at 1071 nm is used to transfer the molecules to lower vibrational levels via optical pumping through the A1Σu+ state. This process transfers the molecules from vibrational levels around ν ~= 113 to a distribution of levels where ν < 35. The molecules may then be further cooled using a broadband superluminescent diode near 685 nm that has its frequency spectrum shaped. The resulting vibrational distributions are probed using resonance-enhanced multiphoton ionization with a pulsed dye laser near 670 nm. The results are presented and compared with theoretical simulations. This work was supported by Fapesp and INCT-IQ.
New Ground-State Crystal Structure of Elemental Boron.
An, Qi; Reddy, K Madhav; Xie, Kelvin Y; Hemker, Kevin J; Goddard, William A
2016-08-19
Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β-B). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β-B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ-B, is based on the Cmcm orthorhombic space group. Quantum mechanics predicts that the newly identified τ-B structure is 13.8 meV/B more stable than β-B. The τ-B structure allows 6% more charge transfer from B_{57} units to nearby B_{12} units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ-B structure to be the ground state structure for elemental boron at atmospheric pressure. PMID:27588864
New Ground-State Crystal Structure of Elemental Boron
NASA Astrophysics Data System (ADS)
An, Qi; Reddy, K. Madhav; Xie, Kelvin Y.; Hemker, Kevin J.; Goddard, William A.
2016-08-01
Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β -B ). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β -B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ -B , is based on the C m c m orthorhombic space group. Quantum mechanics predicts that the newly identified τ -B structure is 13.8 meV /B more stable than β -B . The τ -B structure allows 6% more charge transfer from B57 units to nearby B12 units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ -B structure to be the ground state structure for elemental boron at atmospheric pressure.
Ensemble Theory for Stealthy Hyperuniform Disordered Ground States
NASA Astrophysics Data System (ADS)
Torquato, Salvatore
Disordered hyperuniform many-particle systems have been receiving recent attention because they are distinguishable exotic states of matter poised between a crystal and liquid that are endowed with novel thermodynamic and physical properties. It has been shown numerically that systems of particles interacting with ``stealthy'' bounded, long-ranged pair potentials (similar to Friedel oscillations) have classical ground states that are, counterintuitively, disordered, hyperuniform and highly degenerate. The task of formulating an ensemble theory that yields analytical predictions for the structural characteristics and other properties of stealthy degenerate ground states in d-dimensional Euclidean space is highly nontrivial because the dimensionality of the configuration space depends on the number density and there is a multitude of ways of sampling the ground-state manifold, each with its own probability measure for finding a particular ground-state configuration. A new type of statistical-mechanical theory had to be invented to characterize these exotic states of matter. I report on some initial progress that we have made in this direction. We show that stealthy disordered ground states behave like ''pseudo''-equilibrium hard-sphere systems in Fourier space. Our theoretical predictions for the structure and thermodynamic properties of the stealthy disordered ground states and associated excited states are in excellent agreement with computer simulations across dimensions.
Non-relativistic Limit of Dirac Equations in Gravitational Field and Quantum Effects of Gravity
NASA Astrophysics Data System (ADS)
Wu, Ning
2006-03-01
Based on unified theory of electromagnetic interactions and gravitational interactions, the non-relativistic limit of the equation of motion of a charged Dirac particle in gravitational field is studied. From the Schrödinger equation obtained from this non-relativistic limit, we can see that the classical Newtonian gravitational potential appears as a part of the potential in the Schrödinger equation, which can explain the gravitational phase effects found in COW experiments. And because of this Newtonian gravitational potential, a quantum particle in the earth's gravitational field may form a gravitationally bound quantized state, which has already been detected in experiments. Three different kinds of phase effects related to gravitational interactions are studied in this paper, and these phase effects should be observable in some astrophysical processes. Besides, there exists direct coupling between gravitomagnetic field and quantum spin, and radiation caused by this coupling can be used to directly determine the gravitomagnetic field on the surface of a star.
Woesler, Richard
2007-02-21
The computations of the present text with non-relativistic quantum teleportation equations and special relativity are totally speculative, physically correct computations can be done using quantum field theory, which remain to be done in future. Proposals for what might be called statistical time loop experiments with, e.g., photon polarization states are described when assuming the simplified non-relativistic quantum teleportation equations and special relativity. However, a closed time loop would usually not occur due to phase incompatibilities of the quantum states. Histories with such phase incompatibilities are called inconsistent ones in the present text, and it is assumed that only consistent histories would occur. This is called an exclusion principle for inconsistent histories, and it would yield that probabilities for certain measurement results change. Extended multiple parallel experiments are proposed to use this statistically for transmission of classical information over distances, and regarding time. Experiments might be testable in near future. However, first a deeper analysis, including quantum field theory, remains to be done in future.
Convex Decompositions of Thermal Equilibrium for Non-interacting Non-relativistic Particles
NASA Astrophysics Data System (ADS)
Chenu, Aurelia; Branczyk, Agata; Sipe, John
2016-05-01
We provide convex decompositions of thermal equilibrium for non-interacting non-relativistic particles in terms of localized wave packets. These quantum representations offer a new tool and provide insights that can help relate to the classical picture. Considering that thermal states are ubiquitous in a wide diversity of fields, studying different convex decompositions of the canonical ensemble is an interesting problem by itself. The usual classical and quantum pictures of thermal equilibrium of N non-interacting, non-relativistic particles in a box of volume V are quite different. The picture in classical statistical mechanics is about (localized) particles with a range of positions and velocities; in quantum statistical mechanics, one considers the particles (bosons or fermions) associated with energy eigenstates that are delocalized through the whole box. Here we provide a representation of thermal equilibrium in quantum statistical mechanics involving wave packets with a localized coordinate representation and an expectation value of velocity. In addition to derive a formalism that may help simplify particular calculations, our results can be expected to provide insights into the transition from quantum to classical features of the fully quantum thermal state.
Meta-Atom Behavior in Clusters Revealing Large Spin Ground States.
Hernández Sánchez, Raúl; Betley, Theodore A
2015-11-01
The field of single molecule magnetism remains predicated on super- and double exchange mechanisms to engender large spin ground states. An alternative approach to achieving high-spin architectures involves synthesizing weak-field clusters featuring close M-M interactions to produce a single valence orbital manifold. Population of this orbital manifold in accordance with Hund's rules could potentially yield thermally persistent high-spin ground states under which the valence electrons remain coupled. We now demonstrate this effect with a reduced hexanuclear iron cluster that achieves an S = 19/2 (χ(M)T ≈ 53 cm(3) K/mol) ground state that persists to 300 K, representing the largest spin ground state persistent to room temperature reported to date. The reduced cluster displays single molecule magnet behavior manifest in both variable-temperature zero-field (57)Fe Mössbauer and magnetometry with a spin reversal barrier of 42.5(8) cm(-1) and a magnetic blocking temperature of 2.9 K (0.059 K/min). PMID:26440452
NASA Astrophysics Data System (ADS)
Zhu, X. P.; Zhang, Z. C.; Pushkarev, A. I.; Lei, M. K.
2016-01-01
High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200-300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.
Solving quantum ground-state problems with nuclear magnetic resonance.
Li, Zhaokai; Yung, Man-Hong; Chen, Hongwei; Lu, Dawei; Whitfield, James D; Peng, Xinhua; Aspuru-Guzik, Alán; Du, Jiangfeng
2011-01-01
Quantum ground-state problems are computationally hard problems for general many-body Hamiltonians; there is no classical or quantum algorithm known to be able to solve them efficiently. Nevertheless, if a trial wavefunction approximating the ground state is available, as often happens for many problems in physics and chemistry, a quantum computer could employ this trial wavefunction to project the ground state by means of the phase estimation algorithm (PEA). We performed an experimental realization of this idea by implementing a variational-wavefunction approach to solve the ground-state problem of the Heisenberg spin model with an NMR quantum simulator. Our iterative phase estimation procedure yields a high accuracy for the eigenenergies (to the 10⁻⁵ decimal digit). The ground-state fidelity was distilled to be more than 80%, and the singlet-to-triplet switching near the critical field is reliably captured. This result shows that quantum simulators can better leverage classical trial wave functions than classical computers. PMID:22355607
Chenu, Aurélia; Christensson, Niklas; Kauffmann, Harald F.; Mančal, Tomáš
2013-01-01
A vibronic-exciton model is applied to investigate the recently proposed mechanism of enhancement of coherent oscillations due to mixing of electronic and nuclear degrees of freedom. We study a dimer system to elucidate the role of resonance coupling, site energies, vibrational frequency and energy disorder in the enhancement of vibronic-exciton and ground-state vibrational coherences, and to identify regimes where this enhancement is significant. For a heterodimer representing two coupled bachteriochloropylls of the FMO complex, long-lived vibronic coherences are found to be generated only when the frequency of the mode is in the vicinity of the electronic energy difference. Although the vibronic-exciton coherences exhibit a larger initial amplitude compared to the ground-state vibrational coherences, we conclude that, due to the dephasing of the former, both type of coherences have a similar magnitude at longer population time. PMID:23778355
Global ab initio ground-state potential energy surface of N4
NASA Astrophysics Data System (ADS)
Paukku, Yuliya; Yang, Ke R.; Varga, Zoltan; Truhlar, Donald G.
2013-07-01
We present a global ground-state potential energy surface for N4 suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in N2-N2 collisions. To obtain the surface, complete active space second-order perturbation theory calculations were performed for the ground singlet state with an active space of 12 electrons in 12 orbitals and the maug-cc-pVTZ triple zeta basis set. About 17 000 ab initio data points have been calculated for the N4 system, distributed along nine series of N2 + N2 geometries and three series of N3 + N geometries. The six-dimensional ground-state potential energy surface is fitted using least-squares fits to the many-body component of the electronic energies based on permutationally invariant polynomials in bond order variables.
Stationary phase method and delay times for relativistic and non-relativistic tunneling particles
NASA Astrophysics Data System (ADS)
Bernardini, A. E.
2009-06-01
The stationary phase method is frequently adopted for calculating tunneling phase times of analytically-continuous Gaussian or infinite-bandwidth step pulses which collide with a potential barrier. This report deals with the basic concepts on deducing transit times for quantum scattering: the stationary phase method and its relation with delay times for relativistic and non-relativistic tunneling particles. After reexamining the above-barrier diffusion problem, we notice that the applicability of this method is constrained by several subtleties in deriving the phase time that describes the localization of scattered wave packets. Using a recently developed procedure - multiple wave packet decomposition - for some specifical colliding configurations, we demonstrate that the analytical difficulties arising when the stationary phase method is applied for obtaining phase (traversal) times are all overcome. In this case, we also investigate the general relation between phase times and dwell times for quantum tunneling/scattering. Considering a symmetrical collision of two identical wave packets with an one-dimensional barrier, we demonstrate that these two distinct transit time definitions are explicitly connected. The traversal times are obtained for a symmetrized (two identical bosons) and an antisymmetrized (two identical fermions) quantum colliding configuration. Multiple wave packet decomposition shows us that the phase time (group delay) describes the exact position of the scattered particles and, in addition to the exact relation with the dwell time, leads to correct conceptual understanding of both transit time definitions. At last, we extend the non-relativistic formalism to the solutions for the tunneling zone of a one-dimensional electrostatic potential in the relativistic (Dirac to Klein-Gordon) wave equation where the incoming wave packet exhibits the possibility of being almost totally transmitted through the potential barrier. The conditions for the
Ground-state properties of Ag/sub 2/: A local-density pseudopotential approach
Luis Martins, J.; Andreoni, W.
1983-12-01
The local-density approximation of the density-functional theory is applied to calculate the ground-state properties of Ag/sub 2/, within the framework of the pseudopotential method. The calculated values of the bond length and the harmonic vibrational frequency are in good agreement with experiment. The bonding properties are found to be influenced by the d-electron states in a significant way. The results are compared with those of configuration-interaction calculations.
Ground state and constrained domain walls in Gd /Fe multilayers
NASA Astrophysics Data System (ADS)
Van Aken, Bas B.; Prieto, José L.; Mathur, Neil D.
2005-03-01
The magnetic ground state of antiferromagnetically coupled Gd /Fe multilayers and the evolution of in-plane domain walls is modeled with micromagnetics. The twisted state is characterized by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios MFe:MGd, the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio MFe:MGd but also by the thicknesses of the layers; that is by the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe-aligned and the Gd-aligned state in favor of the twisted state. On the other hand, ultrathin layers exclude the twisted state, since wider domain walls cannot form in these ultrathin layers.
Probing quantum frustrated systems via factorization of the ground state.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2010-05-21
The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures. PMID:20867055
Magnetization ground state and reversal modes of magnetic nanotori
NASA Astrophysics Data System (ADS)
Vojkovic, Smiljan; Nunez, Alvaro S.; Altbir, Dora; Carvalho-Santos, Vagson L.
2016-07-01
In this work, and by means of micromagnetic simulations, we study the magnetic properties of toroidal nanomagnets. The magnetization ground state for different values of the aspect ratio between the toroidal and polar radii of the nanotorus has been obtained. Besides, we have shown that the vortex and the in-plane single domain states can appear as ground states for different ranges of the aspect ratio, while a single domain state with an out-of-plane magnetization is not observed. The hysteresis curves are also obtained, evidencing the existence of two reversal modes depending on the geometry: a vortex mode and a coherent rotation. A comparison between toroidal and cylindrical nanoparticles has been performed evidencing that nanotori can accommodate a vortex as the ground state for smaller volume than cylindrical nanorings.
Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters.
Souza, T X R; Macedo, C A
2016-01-01
In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh's conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653
Phase diagram of the ground states of DNA condensates.
Hoang, Trinh X; Trinh, Hoa Lan; Giacometti, Achille; Podgornik, Rudolf; Banavar, Jayanth R; Maritan, Amos
2015-12-01
The phase diagram of the ground states of DNA in a bad solvent is studied for a semiflexible polymer model with a generalized local elastic bending potential characterized by a nonlinearity parameter x and effective self-attraction promoting compaction. x=1 corresponds to the wormlike chain model. Surprisingly, the phase diagram as well as the transition lines between the ground states are found to be a function of x. The model provides a simple explanation for the results of prior experimental and computational studies and makes predictions for the specific geometries of the ground states. The results underscore the impact of the form of the microscopic bending energy at macroscopic observable scales. PMID:26764619