arXiv subjects

Walber Hugo Brito

Publications and source records attributed to Walber Hugo Brito.

4 recordsLinked to original sources

arXiv2026

Interplay of spin-orbit coupling, crystal field splitting and correlations: a ghost rotationally invariant slave boson treatment

We investigate the interplay of spin-orbit coupling, crystal field splittings, and electronic correlations in the $t_{2g}$ Hubbard-Kanamori model within the recently formulated ghost rotationally invariant slave-boson method (GRISB). In particular, we study a tight binding model of Sr$_2$RuO$_4$ with parameters extracted from density functional theory and linearized quasiparticle self-consistent GW (LQSGW) calculations; we study the behavior of different physical quantities as the number of ghosts increases to examine the convergence of GRISB to dynamical mean field theory (DMFT) and experimental results; and we leverage the ability of GRISB to investigate the model over a wide range of parameters at low temperature. In particular, we examine both static and dynamical observables driven by the spin orbit coupling (SOC) and study how they vary as a function of the Hubbard $U$ and Hund's coupling $J$. GRISB converges quickly for most of these observables, and the calculations reveal the following: $U$ enhances the spin-orbit coupling while $J$ suppresses it. We also study the shape of the Fermi surface within different methodologies, and examine the Lifshitz transition which takes place as a function of strain in this material.

cond-mat.str-el↗

arXiv2023

Provoking topology by octahedral tilting in strained SrNbO$_3$

Transition metal oxides with a wide variety of electronic and magnetic properties offer an extraordinary possibility to be a platform for developing future electronics based on unconventional quantum phenomena, for instance, the topology. The formation of topologically non-trivial states is related to crystalline symmetry, spin-orbit coupling, and magnetic ordering. Here, we demonstrate how lattice distortions and octahedral rotation in SrNbO$_3$ films induce the band topology. By employing angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations, we verify the presence of in-phase $a^0a^0c^+$ octahedral rotation in ultra-thin SrNbO$_3$ films, which causes the formation of topologically-protected Dirac band crossings. Our study illustrates that octahedral engineering can be effectively exploited for implanting and controlling quantum topological phases in transition metal oxides.

cond-mat.mtrl-sci↗

arXiv2023

Orbital Selective Mott Transition Effects and Non-Trivial Topology of Iron Chalcogenide

The iron-based superconductor FeSe$_{1-x}$Te$_{x}$ (FST) has recently gained significant attention as a host of two distinct physical phenomena: ($i$) Majorana zero modes which can serve as potential topologically protected qubits, and ($ii$) a realization of the orbital selective Mott transition (OSMT). In this Letter, we connect these two phenomena and provide new insights into the interplay between strong electronic correlations and non-trivial topology in FST. Using linearized quasiparticle self-consistent GW plus dynamical mean-field theory, we show that the topologically protected Dirac surface state has substantial Fe($d_{xy}$) character. The proximity to the OSMT plays a dual role, it facilitates the appearance of the topological surface state by bringing the Dirac cone close to the chemical potential, but destroys the Z$_{2}$ topological superconductivity when the system is too close to the orbital selective Mott phase (OSMP). We derive a reduced effective Hamiltonian that describes the topological band. Its parameters capture all the chemical trends found in the first principles calculation. Our findings provide a framework for further study of the interplay between strong electronic correlations and non-trivial topology in other iron-based superconductors.

cond-mat.str-el↗

arXiv2023

Octahedral distortions in SrNbO$_3$: Unraveling the structure-property relation

Strontium niobate has triggered a lot of interest as a transparent conductor and as a possible realization of a correlated Dirac semi-metal. Using the lattice parameters as a tunable knob, the energy landscape of octahedral tilting was mapped using density functional theory calculations. We find that biaxial compressive strain induces tilting around the out-of-plane axis, while tensile strain induces tilting around the two in-plane axes. The two competing distorted structures for compressive strain show semi-Dirac dispersions above the Fermi level in their electronic structure. Our density functional theory calculations combined with dynamical mean field theory (DFT+DMFT) reveals that dynamical correlations downshift these semi-Dirac like cones towards the Fermi energy. More generally, our study reveals that the competition between the in-phase and out-of-phase tilting in SrNbO$_3$ provides a new degree of freedom which allows for tuning the thermoelectric and optical properties. We show how the tilt angle and mode is reflected in the behavior of the Seebeck coefficient and the plasma frequency, due to changes in the band structure.

cond-mat.mtrl-sci↗