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1.
D. Gao A. K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):13-22
Electronic structures of double hexagonal close-packed americium and the
(0001) surface have been studied via full-potential all-electron
density-functional calculations with a mixed APW+lo/LAPW basis. The
electronic and geometric properties of bulk dhcp Am as well as quantum size
effects in the surface energies and the work functions of the dhcp Am (0001)
ultra thin films up to seven layers have been examined at nonmagnetic,
ferromagnetic, and antiferromagnetic configurations with and without spin
orbit coupling. The anti-ferromagnetic state including spin-orbit coupling
is found to be the ground state of dhcp Am with the 5f electrons primarily
localized. Our results show that both magnetic configurations and spin-orbit
coupling play important roles in determining the equilibrium lattice
constant, the bulk modulus as well as the localized feature of 5f electrons
for dhcp Am. Our calculated equilibrium lattice constant and bulk modulus at
the ground state are in good agreement with the experimental values
respectively. The work function of dhcp Am (0001) 7-layer surface at the
ground state is predicted to be 2.90 eV. The surface energy for dhcp Am
(0001) semi-infinite surface energy at the ground state is predicted to be
0.84 J/m2. Quantum size effects are found to be more pronounced in work
functions than in surface energies. 相似文献
2.
A.K. Ray J.C. Boettger 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):429-433
The linear combinations of Gaussian type orbitals fitting function (LCGTO-FF) method is used to study the electronic and geometrical
properties of plutonium monolayers with square and hexagonal symmetry. The effects of several common approximations are examined:
(1) scalar-relativity vs. full-relativity (i.e., with spin-orbit coupling included); (2) paramagnetic vs. spin-polarized; and (3) local-density approximation (LDA) vs. generalized- gradient approximation (GGA). The results indicate that spin-orbit coupling has a much stronger effect on the
monolayer properties compared to the effects of spin-polarization. In general, the GGA is found to predict a larger lattice
constant and a smaller cohesive energy compared to LDA predictions. We also find a significant compression of the monolayers
compared to the bulk, contradicting the only other published result on a Pu monolayer. The current result supports the existence
of a δ-like surface on α-Pu.
Received 17 October 2001 Published online 6 June 2002 相似文献
3.
P. P. Dholabhai R. Atta-Fynn A. K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):261-270
Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen
and oxygen chemisorption on the (0001) surface of double hexagonal packed americium using a full-potential all-electron linearized
augmented plane wave plus local orbitals method. Chemisorption energies were optimized with respect to the distance of the
adatom from the relaxed surface for three adsorption sites, namely top, bridge, and hollow hcp sites, the adlayer structure
corresponding to coverage of a 0.25 monolayer in all cases. Chemisorption energies were computed at the scalar-relativistic
level (no spin-orbit coupling NSOC) and at the fully relativistic level (with spin-orbit coupling SOC). The two-fold bridge
adsorption site was found to be the most stable site for O at both the NSOC and SOC theoretical levels with chemisorption
energies of 8.204 eV and 8.368 eV respectively, while the three-fold hollow hcp adsorption site was found to be the most stable
site for H with chemisorption energies of 3.136 eV at the NSOC level and 3.217 eV at the SOC level. The respective distances
of the H and O adatoms from the surface were found to be 1.196 ?and 1.164 ?. Overall our calculations indicate that chemisorption
energies in cases with SOC are slightly more stable than the cases with NSOC in the 0.049–0.238 eV range. The work functions
and net magnetic moments respectively increased and decreased in all cases compared with the corresponding quantities of bare
dhcp Am (0001) surface. The partial charges inside the muffin-tins, difference charge density distributions, and the local
density of states have been used to analyze the Am-adatom bond interactions in detail. The implications of chemisorption on
Am 5f electron localization-delocalization are also discussed. 相似文献
4.
We present experimental and theoretical evidence of the role played by the spin–orbit coupling in the electronic structure of a pseudomorphic Au monolayer on Nb(001) substrate. The bands found with the help of the angle‐resolved ultraviolet photoelectron spectroscopy (ARUPS) are compared with those obtained from ab initio self‐consistent calculations by the VASP and WIEN2k codes. The slab calculations are performed including geometric relaxation and using both the generalized‐gradient (GGA) and local‐density (LDA) approximations for the exchange–correlation energy. The dispersions and energy positions of the calculated bands agree with the experimentally determined band structure only if the LDA is used and the spin–orbit coupling is included. Therefore, both the structure relaxation and spin–orbit coupling are essential in understanding the electronic structure of the Au/Nb(001) system.
5.
6.
《中国物理快报》2021,(8)
The persistent spin helix(PSH) system is considered to have promising applications in energy-conservation spintronics because it supports an extraordinarily long spin lifetime of carriers.Here,we predict that the existence of PSH state in two-dimensional(2 D) ferroelectric NbOI_2 monolayers.Our first-principles calculation results show that there exists Dresselhaus-type spin-orbit coupling(SOC) band splitting near the conduction-band minimum(CBM) of the NbOI_2 monolayer.It is revealed that the spin splitting near CBM merely refers to out-of-plane spin configuration in the wave vector space,which gives rise to a long-lived PSH state that can be controlled by reversible ferroelectric polarization.We believe that the coupling characteristics of ferroelectric polarization and spin texture in NbOI_2 provide a platform for the realization of fully electric controlled spintronic devices. 相似文献
7.
Y. Benmimoun A. Bouhemadou R. Khenata A. H. Reshak B. Amrani M. Ameri H. Baltache 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):165-171
The results of first-principles theoretical study of the structural,
electronic and optical properties of SrCl2 in its cubic structure, have
been performed using the full-potential linear augmented plane-wave method
plus local orbitals (FP-APW+lo) as implemented in the WIEN2k code. In this
approach both the local density approximation (LDA) and the generalized
gradient approximation (GGA) are used for the exchange-correlation (XC)
potential. Also we have used the Engel-Vosko GGA formalism, which optimizes
the corresponding potential for band structure calculations. We performed
these calculations with and without spin-orbit interactions. Including
spin-orbit coupling cause to lifts the triple degeneracy at Γ point
and a double degeneracy at X point. Results are given for structural
properties. The pressure dependence of elastic constants and band gaps are
investigated. The dielectric function, reflectivity spectra and refractive
index are calculated up to 30 eV. Also we calculated the pressure and volume
dependence of the static optical dielectric constant. 相似文献
8.
Mohammed Lach-habDimitrios A. Papaconstantopoulos Michael J. Mehl 《Journal of Physics and Chemistry of Solids》2002,63(5):833-841
In this work, we have extended our study of the mechanical properties and the electronic structure of PbTe to include other Pb chalcogenide compounds (PbSe, PbS). The calculations were performed self-consistently using the scalar-relativistic full-potential linearized augmented plane wave method. Both the local density approximation (LDA) and the generalized gradient approximation (GGA) to density-functional theory were applied.The equilibrium lattice constants and the bulk modulus of a number of structures (NaCl, CsCl, ZnS) were calculated as well as the elastic constants for the structures (NaCl, CsCl). The NaCl structure is found to be the most stable one among all the three phases considered. We have found that the GGA predicts the elastic constants in good agreement with experimental data.Both the LDA and GGA were successful in predicting the location of the band gap at the L point of the Brillouin zone but they are inconclusive regarding the value of the band-gap width. To resolve the issue of the gap, we performed Slater-Koster (SK) tight-binding calculations, including the spin-orbit coupling in the SK Hamiltonian. The SK results that are based on our GGA calculations give the best agreement with experiment.Results are reported for the pressure dependence of the energy gap of these compounds in the NaCl structure. The pressure variation of the energy gap indicates a transition to a metallic phase at high pressure. Band structure calculations in the CsCl structure show a metallic state for all compounds. The electronic band structure in the ZnS phase shows an indirect band gap at the W and X point of the Brillouin zone. 相似文献
9.
Mohammad Reza Khayatzadeh Mahani 《Physics letters. A》2008,372(38):6022-6025
The influence of in-plane magnetic field on spin polarization in the presence of the oft-neglected k3-Dresselhaus spin-orbit coupling was investigated. The k3-Dresselhaus term can produce a limited spin polarization. The in-plane magnetic field plays a great role in the tunneling process. It can generate the perfect spin polarization of the electrons and the ideal transmission coefficient for spin up and down simultaneously. In energy scale, complete separation between spin up and down resonance was obtained by a relatively higher in-plane magnetic field while a comparatively lower in-plane magnetic field vanishes the spin separation. On the other hand, the spin relaxation can be suppressed by compensating the oft-neglected k3-Dresselhaus spin orbit coupling using a relatively lower in-plane magnetic field. 相似文献
10.
S. Bhattacharjee S. M. Jaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):305-311
The influence of correlation and temperature on the electronic structure of bulk and
thin film GdN
has been studied using the s-f model, which combines
the one electron band structure with a many body procedure.
The tight binding linear muffin tin orbital (TB-LMTO) method was used to obtain
the one electron band structure of
the system. The s-f exchange coupling constants
for each band were obtained from the spin polarized band structure of
the system using a mean field model.
Correlation effects are found to be present in the system. However they
are not sufficiently strong to cause a correlation induced splitting in the
spectrum. Some bands of the thin films of GdN exhibit splitting at T=Tc
and it is due to the combined effect
of correlation and temperature. The conduction bands of both the bulk and
the thin films of GdN exhibit a red shift with respect to temperature. 相似文献
11.
We theoretically investigate the electron transport properties in a non-magnetic heterostructure with both Dresselhaus and Rashba spin-orbit interactions. The detailed-numerical results show that (1) the large spin polarization can be achieved due to Dresselhaus and Rashba spin-orbit couplings induced splitting of the resonant level, although the magnetic field is zero in such a structure, (2) the Rashba spin-orbit coupling plays a greater role on the spin polarization than the Dresselhaus spin-orbit interaction does, and (3) the transmission probability and the spin polarization both periodically change with the increase of the well width. 相似文献
12.
Consistency in formulation of spin current and torque associated with a variance of angular momentum
Based on the Noether's theorem, we develop systematically and rigorously the spin-dependent formulation of the conservation laws. The effect of the electronic polarization due to the spin-orbit coupling is included in the Maxwell equations. The polarization is related to the antisymmetric components of spin current, and it provides a possibility to measure the spin current directly. The variances of spin and orbit angular momentum currents imply a torque on the "electric dipole" associated with the moving electron. The dependencies of the torque on the polarization and the force on the motions of spin-polarized electrons in a two-dimensional electron gas with the Rashba spin-orbit coupling are discussed. 相似文献
13.
A study on characteristics of electrons tunneling through semiconductor barrier is evaluated, in which we take into account the effects of Rashba spin-orbit interaction. Our numerical results show that Rashba spin-orbit effect originating from the inversion asymmetry can give rise to the spin polarization. The spin polarization does not increase linearly but shows obvious resonant features as the strength of Rashba spin-orbit coupling increases, and the amplitudes of spin polarization can reach the highest around the first resonant energy level. Furthermore, it is found that electrons with different spin orientations will spend quite different time through the same heterostructures. The difference of the dwell time between spin-up and spin-down electrons arise from the Rashba spin-orbit coupling. And it is also found that the dwell time will reach its maximum at the first resonant energy level. It can be concluded that, in the time domain, the tunneling processes of the spin-up and spin-down electrons can be separated by modulating the strength of Rashba spin-orbit coupling. Study results indicate that Rashba spin-orbit effect can cause a nature spin filter mechanism in the time domain. 相似文献
14.
G. H. Liu Y. H. Chen C. H. Jia Z. G. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):397-401
We theoretically study the spatial behaviors of spin precessions modulated by an effective magnetic field in a two-dimensional
electron system with spin-orbit interaction. Through analysis of
interaction between the spin and the effective magnetic field, we find some laws of spin precession in the system, by which
we explain some previous phenomena of spin precession, and predict a controllable electron spin polarization wave in [001]-grown
quantum wells. The shape of the wave, like water wave, mostly are ellipse-like or circle-like, and the wavelength is anisotropic
in the quantum wells with two unequal coupling strengths of the Rashba and Dresselhaus interactions, and is isotropic in the
quantum wells with only one spin orbit interaction. 相似文献
15.
The influence of the Dresselhaus spin-orbit coupling on spin polarization by tunneling through a disordered semiconductor superlattice was investigated. The Dresselhaus spin-orbit coupling causes the spin polarization of the electron due to transmission possibilities difference between spin up and spin down electrons. The electron tunneling through a zinc-blende semiconductor superlattice with InAs and GaAs layers and two variable distance InxGa(1−x)As impurity layers was studied. One hundred percent spin polarization was obtained by optimizing the distance between two impurity layers and impurity percent in disordered layers in the presence of Dresselhaus spin-orbit coupling. In addition, the electron transmission probability through the mentioned superlattice is too much near to one and an efficient spin filtering was recommended. 相似文献
16.
M. Ilkhani M. R. Abolhassani M. Aslaninejad 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):21-28
The impacts of pressure on the structural and electronic properties of CeIn3 have been calculated. The calculations are performed in the presence and the absence of spin-orbit interaction as well as
GGA+U using density functional theory within the PBE-GGA approximation. It is shown that energy and density of states analyses
are considerably influenced by the spin-orbit interaction. The spin and orbital magnetic moments of Ce are calculated under
pressure up to 22 GPa. An almost linear relation is observed between the magnetic moment and the density of states of Ce-4f at Fermi level. At ambient pressure, a good agreement between the values of the electric field gradients, EFG, and bulk modulus
with experimental results is observed. The strongest anisotropy in charge distribution originates from In-5p orbital, which has the main contribution to EFG. 相似文献
17.
《Current Applied Physics》2019,19(12):1362-1366
Based on a spin drift-diffusion model, we theoretically investigate the spin-orbit torque in ferromagnet/normal metal/insulator trilayers with considering the Rashba interfacial spin-orbit coupling at the normal metal/insulator interface. We find that the spin-orbit torque shows the opposite normal-metal-thickness dependences for the bulk spin-orbit coupling effect in the normal metal layer and for the interfacial spin-orbit coupling effect at the normal metal/insulator interface, offering a way to disentangle these two spin-orbit coupling effects. Moreover, we show that the conventional interpretation based on the bulk spin-orbit coupling effect overestimates the spin Hall angle and underestimates the spin diffusion length of the normal metal layer, when the interfacial contribution is non-negligible. Our result, a concise analytic expression of the spin-orbit torque considering both bulk and interface spin-orbit coupling effects, will be useful to design and interpret experiments on spin-orbit torque experiments in ferromagnet/normal metal/insulator trilayers. 相似文献
18.
We present a combined experimental (angle resolved photoemission: ARUPS) and theoretical study of the Shockley-type surface state in the L-gap of the (1 1 1)-face of Au covered with one monolayer of Ar. As known also from other systems consisting of rare-gas monolayers on noble metal (1 1 1) surfaces, the adsorbed rare-gas shifts the Shockley-state towards the Fermi level and increases the spin-orbit splitting, whereas the effective band mass remains unchanged. We analyze the observed changes by a comparison with ab initio slab-layer calculations based on the density functional theory (DFT), both within the local density approximation (LDA) and the generalized gradient approximation (GGA). Although the attractive van der Waals interaction between rare-gas and substrate is not properly considered in DFT there are considerable hybridization effects which allow to describe such weakly bound adsorbates quantitatively. We show to what extent the various DFT calculations correspond to the experimental results. Furthermore, we discuss the importance of lattice relaxation and the exact absorption position into the calculations. 相似文献
19.
The atomic and electronic structures of a graphene monolayer on a Ru(0001)
surface under compressive strain are investigated by using
first-principles calculations. Three models of graphene monolayers
with different carbon periodicities due to the lattice mismatch are proposed in the presence and the absence of the Ru(0001) substrate separately. Considering the strain induced by the lattice mismatch, we optimize the atomic structures and investigate the electronic properties of the graphene. Our calculation results show that the graphene layers turn into periodic corrugations and there exist strong chemical bonds in the interface between the graphene N×N superlattice and the substrate. The strain does not induce significant changes in electronic structure. Furthermore, the results calculated in the local density approximation (LDA) are compared with those obtained in the generalized gradient approximation (GGA), showing that the LDA results are more reasonable than the GGA results when only two substrate layers are used in calculation. 相似文献
20.
We study the effect of Rashba spin-orbit coupling on the Hofstadter spectrum of a two-dimensional tight-binding electron system in a perpendicular magnetic field. We obtain the generalized coupled Harper spin-dependent equations which include the Rashba spin-orbit interaction and solve for the energy spectrum and spin polarization. We investigate the effect of spin-orbit coupling on the fractal energy spectrum and the spin polarization for some characteristic states as a function of the magnetic flux α and the spin-orbit coupling parameter. We characterize the complexity of the fractal geometry of the spin-dependent Hofstadter butterfly with the correlation dimension and show that it grows quadratically with the amplitude of the spin-orbit coupling. We study some ground state properties and the spin polarization shows a fractal-like behavior as a function of α, which is demonstrated with the exponent close to unity of the decaying power spectrum of the spin polarization. Some degree of spin localization or distribution around +1 or -1, for small spin-orbit coupling, is found with the determination of the entropy function as a function of the spin-orbit coupling. The excited states show a more extended (uniform) distribution of spin states. 相似文献