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Register a new userGW quasiparticle calculations with spin-orbit coupling for the light actinides
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We report on the importance of GW self-energy corrections for the electronic structure of light actinides in the weak-to-intermediate coupling regime. Our study is based on calculations of the band structure and total density of states of Np, U, and Pu using a one-shot GW approximation that includes spin-orbit coupling within a full potential LAPW framework. We also present RPA screened effective Coulomb interactions for the f-electron orbitals for different lattice constants, and show that there is an increased contribution from electron-electron correlation in these systems for expanded lattices. We find a significant amount of electronic correlation in these highly localized electronic systems.
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Finding an accurate ab initio approach for calculating the electronic properties of transition metal oxides has been a problem for several decades. In this paper, we investigate the electronic structure of the transition metal monoxides MnO, CoO, and NiO in their undistorted rock-salt structure within a fully iterated quasiparticle self-consistent GW (QPscGW) scheme. We study the convergence of the QPscGW method, i.e., how the quasiparticle energy eigenvalues and wavefunctions converge as a function of the QPscGW iterations, and we compare the converged outputs obtained from different starting wavefunctions. We find that the convergence is slow and that a one-shot G$_0$W$_0$ calculation does not significantly improve the initial eigenvalues and states. It is important to notice that in some cases the path to convergence may go through energy band reordering which cannot be captured by the simple initial unperturbed Hamiltonian. When we reach a fully iterated solution, the converged density of states, band-gaps and magnetic moments of these oxides are found to be only weakly dependent on the choice of the starting wavefunctions and in reasonably good agreement with the experiment. Finally, this approach provides a clear picture of the interplay between the various orbitals near the Fermi level of these simple transition metal monoxides. The results of these accurate {it ab initio} calculations can provide input for models aiming at describing the low energy physics in these materials.
Within the framework of the full potential projector-augmented wave methodology, we present a promising low-scaling $GW$ implementation. It allows for quasiparticle calculations with a scaling that is cubic in the system size and linear in the number of $k$ points used to sample the Brillouin zone. This is achieved by calculating the polarizability and self-energy in the real space and imaginary time domain. The transformation from the imaginary time to the frequency domain is done by an efficient discrete Fourier transformation with only a few nonuniform grid points. Fast Fourier transformations are used to go from real space to reciprocal space and vice versa. The analytic continuation from the imaginary to the real frequency axis is performed by exploiting Thieles reciprocal difference approach. Finally, the method is applied successfully to predict the quasiparticle energies and spectral functions of typical semiconductors (Si, GaAs, SiC, and ZnO), insulators (C, BN, MgO, and LiF), and metals (Cu and SrVO$_3$). The results are compared with conventional $GW$ calculations. Good agreement is achieved, highlighting the strength of the present method.
We present quasiparticle (QP) energies from fully self-consistent $GW$ (sc$GW$) calculations for a set of prototypical semiconductors and insulators within the framework of the projector-augmented wave methodology. To obtain converged results, both finite basis-set corrections and $k$-point corrections are included, and a simple procedure is suggested to deal with the singularity of the Coulomb kernel in the long-wavelength limit, the so called head correction. It is shown that the inclusion of the head corrections in the sc$GW$ calculations is critical to obtain accurate QP energies with a reasonable $k$-point set. We first validate our implementation by presenting detailed results for the selected case of diamond, and then we discuss the converged QP energies, in particular the band gaps, for a set of gapped compounds and compare them to single-shot $G_0W_0$, QP self-consistent $GW$, and previously available sc$GW$ results as well as experimental results.
We chart out the phase diagram of ultracold `spin-half bosons in a one-dimensional optical lattice in the presence of Aubry-Andre (AA) potential and with spin-orbit (SO) and Raman couplings investigating the transition from superfluid (SF) to localized phases and the existence of density wave phase for nearest-neighbor interaction (NNI). We show that the presence of SO coupling and AA potential leads to a novel spin-split momentum distribution of the bosons in the localized phase near the boundary with the SF phase, which can act as a signature of such a transition. We also obtain the level statistics of the bosons in the superfluid phase with finite NNI and demonstrate its change from Gaussian Unitary Ensemble (GUE) to Gaussian Orthogonal Ensemble (GOE) as a function of the Raman coupling. We discuss experiments which can test our theory.
A hole injected into a Mott insulator will gain an internal structure as recently identified by exact numerics, which is characterized by a nontrivial quantum number whose nature is of central importance in understanding the Mott physics. In this work, we show that a spin texture associated with such an internal degree of freedom can explicitly manifest after the spin degeneracy is lifted by a emph{weak} Rashba spin-orbit coupling (SOC). It is described by an emergent angular momentum $J_{z}=pm3/2$ as shown by both exact diagonalization (ED) and variational Monte Carlo (VMC) calculations, which are in good agreement with each other at a finite size. In particular, as the internal structure such a spin texture is generally present in the hole composite even at high excited energies, such that a corresponding texture in momentum space, extending deep inside the Brillouin zone, can be directly probed by the spin-polarized angle-resolved photoemission spectroscopy (ARPES). This is in contrast to a Landau quasiparticle under the SOC, in which the spin texture induced by SOC will not be protected once the excited energy is larger than the weak SOC coupling strength, away from the Fermi energy. We point out that the spin texture due to the SOC should be monotonically enhanced with reducing spin-spin correlation length in the superconducting/pseudogap phase at finite doping. A brief discussion of a recent experiment of the spin-polarized ARPES will be made.
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