GW method applied to localized 4f electron systems

We apply a recently developed quasiparticle self-consistent $GW$ method (QSGW) to Gd, Er, EuN, GdN, ErAs, YbN and GdAs. We show that QSGW combines advantages separately found in conventional $GW$ and LDA+$U$ theory, in a simple and fully \emph{ab initio} way. \qsgw reproduces the experimental occupied $4f$ levels well, though unoccupied levels are systematically overestimated. Properties of the Fermi surface responsible for electronic properties are in good agreement with available experimental data. GdN is predicted to be very near a critical point of a first-order metal-insulator transition.Comment: 5 pages,3 figures, 2 table

Ab-initio Prediction of Conduction Band Spin Splitting in Zincblende Semiconductors

We use a recently developed self-consistent $GW$ approximation to present systematic \emph{ab initio} calculations of the conduction band spin splitting in III-V and II-V zincblende semiconductors. The spin orbit interaction is taken into account as a perturbation to the scalar relativistic hamiltonian. These are the first calculations of conduction band spin splittings based on a quasiparticle approach; and because the self-consistent $GW$ scheme accurately reproduces the relevant band parameters, it is expected to be a reliable predictor of spin splittings. The results are compared to the few available experimental data and a previous calculation based on a model one-particle potential. We also briefly address the widely used {\bf k}$\cdot${\bf p} parameterization in the context of these results.Comment: 9 pages, 1 figur

GW correlation effects on plutonium quasiparticle energies: changes in crystal-field splitting

We present results for the electronic structure of plutonium by using a recently developed quasiparticle self-consistent $GW$ method (\qsgw). We consider a paramagnetic solution without spin-orbit interaction as a function of volume for the face-centered cubic (fcc) unit cell. We span unit-cell volumes ranging from 10% greater than the equilibrium volume of the $\delta$ phase to 90 % of the equivalent for the $\alpha$ phase of Pu. The self-consistent $GW$ quasiparticle energies are compared to those obtained within the Local Density Approximation (LDA). The goal of the calculations is to understand systematic trends in the effects of electronic correlations on the quasiparticle energy bands of Pu as a function of the localization of the $f$ orbitals. We show that correlation effects narrow the $f$ bands in two significantly different ways. Besides the expected narrowing of individual $f$ bands (flatter dispersion), we find that an even more significant effect on the $f$ bands is a decrease in the crystal-field splitting of the different bands.Comment: 9 pages, 7 figures, 3 table

Ab-initio calculations of spin tunneling through an indirect barrier

We use a fully relativistic layer Green's functions approach to investigate spin-dependent tunneling through a symmetric indirect band gap barrier like GaAs/AlAs/GaAs heterostructure along [100] direction. The method is based on Linear Muffin Tin Orbitals and it is within the Density Functional Theory (DFT) in the Local Density Approximation (LDA). We find that the results of our {\it ab-initio} calculations are in good agreement with the predictions of our previous empirical tight binding model [Phys. Rev. {\bf B}, 075313 (2006)]. In addition we show the $k_{||}$-dependence of the spin polarization which we did not previously include in the model. The {\it ab-initio} calculations indicate a strong $k_{||}$-dependence of the transmission and the spin polarization due to band non-parabolicity. A large window of 25-50 % spin polarization was found for a barrier of 8 AlAs monolayers at $k_{||}$ = 0.03 $2\pi/a$. Our calculations show clearly that the appearance of energy windows with significant spin polarization depends mostly on the location of transmission resonances and their corresponding zeros and not on the magnitude of the spin splitting in the barrier.Comment: 10 pages, 3 figure

Spin tunneling through an indirect barrier

Spin-dependent tunneling through an indirect bandgap barrier like the GaAs/AlAs/GaAs heterostructure along [001] direction is studied by the tight-binding method. The tunneling is characterized by the proportionality of the Dresselhaus Hamiltonians at $\Gamma$ and $X$ points in the barrier and by Fano resonances. The present results suggest that large spin polarization can be obtained for energy windows that exceed significantly the spin splitting. We also formulate two conditions that are necessary for the existence of energy windows with large polarization.Comment: 19 pages, 7 figure

Detection of the spin character of Fe(001) surface states by scanning tunneling microscopy: A theoretical proposal

We consider the magnetic structure on the Fe(001) surface and theoretically study the scanning tunneling spectroscopy using a spin-polarized tip (SP-STM). We show that minority-spin surface states induce a strong bias dependence of the tunneling differential conductance which largely depends on the orientation of the magnetization in the SP-STM tip relative to the easy magnetization axis in the Fe(001) surface. We propose to use this effect in order to determine the spin character of the Fe(001) surface states. This technique can be applied also to other magnetic surfaces in which surface states are observed.Comment: 5 pages, 4 figure

Incommensurate spin resonance in URu2Si2

We focus on inelastic neutron scattering in $URu_2Si_2$ and argue that observed gap in the fermion spectrum naturally leads to the spin feature observed at energies $\omega_{res} = 4-6 meV$ at momenta at \bQ^* = (1\pm 0.4, 0,0). We discuss how spin features seen in $URu_2Si_2$ can indeed be thought of in terms of {\em spin resonance} that develops in HO state and is {\em not related} to superconducting transition at 1.5K. In our analysis we assume that the HO gap is due to a particle-hole condensate that connects nested parts of the Fermi surface with nesting vector $\bf{Q}^*$. Within this approach we can predicted the behavior of the spin susceptibility at \bQ^* and find it to be is strikingly similar to the phenomenology of resonance peaks in high-T$_c$ and heavy fermion superconductors. The energy of the resonance peak scales with $T_{HO}$ $\omega_{res} \simeq 4 k_BT_{HO}$. We discuss observable consequences spin resonance will have on neutron scattering and local density of states.Comment: 8 pgaes latex, 4 fig

Many-body Electronic Structure of Metallic alpha-Uranium

We present results for the electronic structure of alpha uranium using a recently developed quasiparticle self-consistent GW method (QSGW). This is the first time that the f-orbital electron-electron interactions in an actinide has been treated by a first-principles method beyond the level of the generalized gradient approximation (GGA) to the local density approximation (LDA). We show that the QSGW approximation predicts an f-level shift upwards of about 0.5 eV with respect to the other metallic s-d states and that there is a significant f-band narrowing when compared to LDA band-structure results. Nonetheless, because of the overall low f-electron occupation number in uranium, ground-state properties and the occupied band structure around the Fermi energy is not significantly affected. The correlations predominate in the unoccupied part of the f states. This provides the first formal justification for the success of LDA and GGA calculations in describing the ground-state properties of this material.Comment: 4 pages, 3 fihgure

The Electronic Correlation Strength of Pu

An electronic quantity, the correlation strength, is defined as a necessary step for understanding the properties and trends in strongly correlated electronic materials. As a test case, this is applied to the different phases of elemental Pu. Within the GW approximation we have surprisingly found a "universal" scaling relationship, where the f-electron bandwidth reduction due to correlation effects is shown to depend only on the local density approximation bandwidth and is otherwise independent of crystal structure and lattice constant.Comment: 7 pages, 4 figures, This version of the paper has been revised to add additional background informatio

Strain-Induced Conduction Band Spin Splitting in GaAs from First Principles Calculations

We use a recently developed self-consistent GW approximation to present first principles calculations of the conduction band spin splitting in GaAs under [110] strain. The spin orbit interaction is taken into account as a perturbation to the scalar relativistic hamiltonian. These are the first calculations of conduction band spin splitting under deformation based on a quasiparticle approach; and because the self-consistent GW scheme accurately reproduces the relevant band parameters, it is expected to be a reliable predictor of spin splittings. We also discuss the spin relaxation time under [110] strain and show that it exhibits an in-plane anisotropy, which can be exploited to obtain the magnitude and sign of the conduction band spin splitting experimentally.Comment: 8 pages, 4 figures, 1 tabl