arXiv subjects

I. A. Shvets

Publications and source records attributed to I. A. Shvets.

3 recordsLinked to original sources

arXiv2026

A unified tight-binding description of the electronic structure and Ising protection of superconductivity in misfit layered compounds

Misfit layered compounds (MLCs) offer a unique bulk platform for realizing exotic quantum states typically associated with two-dimensional transition-metal dichalcogenides (TMDs), most notably Ising-protected superconductivity. Yet a theoretical description capturing their electronic structure beyond the simplistic picture of electronically isolated TMD layers has been lacking. Here, we develop a unified tight-binding model for metal dichalcogenide-based MLCs, parameterized by extensive density-functional theory (DFT) calculations across multiple structural configurations and chemical compositions. We show that the intervening tetragonal layers play an active role beyond charge reservoirs: they mediate a significant interlayer spin-orbit coupling entirely absent in the standard rigid-band picture. This emergent interlayer spin-orbit coupling is essential for reproducing the DFT band structure of bulk MLCs and, when incorporated into Bogoliubov--de Gennes calculations, provides a microscopic mechanism for the Ising protection of superconductivity by strongly enhancing the in-plane critical field. Our framework establishes MLCs as a distinct class of three-dimensional materials with intrinsically coupled layers and emergent spin-orbit phenomena.

cond-mat.supr-con↗

arXiv2026

Anomalous phase shift and superconducting diode effect in Josephson junctions via thin films of rare-earth intermetallic magnets

The superconductor/ferromagnet/superconductor (S/F/S) Josephson junctions (JJs) with an anomalous ground state phase shift $φ_0 \neq 0,π$ ($φ_0$-S/F/S JJs) enable the implementation of the zero-field Josephson diode effect with the possibility to control the diode efficiency and polarity. It is just as important that in this case $φ_0$ provides a coupling between the superconducting phase and the magnetization of the interlayer. Such $φ_0$-S/F/S JJs can be used for superconducting memory and logic circuit applications. Here we present the results of theoretical calculation of the current-phase relationship (CPR), exhibiting the Josephson diode effect and $φ_0\neq 0,π$, for a JJ through a specific magnetic material. As the interlayer of the JJ we consider an ultra-thin film of intermetallic lanthanide ($Ln$)-based compound $\mathrm{GdIr_2Si_2}$. Using the density functional theory (DFT) methods, we study the electronic structure and magnetic properties of the film. Then the effective tight-binding Hamiltonian (TBH), demonstrating high quantitative consistency with the electronic properties obtained from DFT calculations, is constructed. The TBH is used to calculate CPR in the framework of the Bogolubov-de Gennes approach. The CPRs demonstrate a pronounced $φ_0$ of the order of unity and a pronounced Josephson diode effect with the diode efficiency $ \lesssim 0.3$. Moreover, the efficiency can be controlled via rotation of in-plane magnetization in the interlayer. The prospects for utilizing alternative magnetic $Ln$-based materials of the $LnT_2X_2$ family ($T$ is a transition metal and $X$ is a $p$-element from groups III-V) for the implementation in $φ_0$-S/F/S JJs are also discussed.

cond-mat.supr-con↗

arXiv2024

Interplay between surface Dirac and Rashba states specific for topologically nontrivial van der Waals superlattices

Here we show that, in contrast to the observed surface states in well studied pnictogen chalcogenide van der Waals (vdW) topological insulators (TIs) with quintuple layer (QL) or septuple layer~(SL) structure, in superlattices, comprising the alternating QL and SL vdW blocks, the Dirac state becomes accompanied by emergent spin-polarized states of the Rashba type. This specific feature is caused by an inequivalence of the surface and subsurface structural blocks and an electrostatic potential bending near the surface. Within density functional theory~(DFT) and $\emph{ab-initio}$ tight-binding~(TB) calculations we analyze peculiarities of these states depending on the surface termination, structural parameters and chemical composition. It is found that their possible hybridization with the Dirac state significantly affects its dispersion and spatial localization. We analyze the influence of intrinsic magnetism on behavior of the termination-dependent surface states for magnetic QL/SL superlattices. These findings provide a better understanding of the existing experimental observations of such QL/SL alternating superlattices.

cond-mat.mtrl-sci↗