arXiv subjects

Igor R. Shein

Publications and source records attributed to Igor R. Shein.

4 recordsLinked to original sources

arXiv2025

Universal negative magnetoresistance in antiferromagnetic metals caused by symmetry breaking of electron wave functions

Layered van der Waals crystals of topologically non-trivial and trivial semimetals with antiferromagnetic (AFM) ordering of magnetic sublattice are known to exhibit a negative magnetoresistance that is well correlated with AFM magnetization changes in a magnetic field. This effect is reported in several experimental studies with EuFe2As2, EuSn2As2, EuSn2P2, etc., where the resistance decreases quadratically with field by about 5% up to the spin-polarization field. Although this effect is well documented experimentally, its theoretical explanation is missing up to date. Here, we propose a theoretical mechanism describing the observed magnetoresistance that is inherent in AFM metals and is based on violation the binary T2 symmetry. It is almost isotropic to the field and current directions, contrary to the known mechanisms such as giant magnetoresistance and chiral anomaly. The proposed intrinsic mechanism of magnetoresistance is strong in a wide class of the layered AFM-ordered semimetals. The theoretically calculated magnetoresistance is qualitatively consistent with experimental data for crystals of various composition.

cond-mat.str-el↗

arXiv2023

Anatomy of the band structure of the newest apparent near-ambient superconductor LuH$_{3-x}$N$_x$

Recently it was claimed that nitrogen-doped lutetium hydride exhibited a near-ambient superconducting transition with a temperature of 294 K at a pressure of only 10 kbar, this pressure being several orders of magnitude lower than previously demonstrated for hydrides under pressure. In this paper, we investigate within DFT+U the electronic structure of both parent lutetium hydride LuH$_3$ and nitrogen doped lutetium hydride LuH$_{2.75}$N$_{0.25}$. We calculated corresponding bands, density of states and Fermi surfaces. It is shown that in the stoichiometric system the Lu-5d states cross the Fermi level while the H-1s states make almost no contribution at the Fermi level. However, with nitrogen doping, the N-2p states enter the Fermi level in large quantities and bring together a significant contribution from the H-1s states. The presence of N-2p and H-1s states at the Fermi level in a doped compound can facilitate the emergence of superconductivity. For instance, nitrogen doping almost doubles the value of DOS at the Fermi level. Simple BCS analysis shows that the nitrogen doping of LuH$_3$ can provide T$_c$ more than 100K and even increase it with further hole doping.

cond-mat.supr-con↗

arXiv2011

Structural, electronic properties and Fermi surface of ThCr2Si2-type charge-balanced KFe2AsSe phase as a parent system for a new group of "mixed" pnictide-chalcogenide superconductors

The ThCr2Si2-type arsenide-selenide phase KFe2AsSe is proposed as a parent system for a new "intermediate" group of Fe-based superconducting materials bridging the known families of Fe-pnictides (such as BaFe2As2) and Fe-chalcogenides (such as KxFe2-ySe2) superconductors. The characterization of the proposed charge-balanced phase by means of FLAPW-GGA approach covers the crystal structure, As/Se atomic ordering, stability, electronic bands, Fermi surface, and density of electronic states.

cond-mat.supr-con↗

arXiv2011

Stability, structural, elastic and electronic properties of polymorphs of the superconducting disilicide YIr2Si2

Using the ab initio approaches, the comparative stability, structural, elastic, and electronic properties of three polymorphs of the superconducting disilicide YIr2Si2, which differ in the atomic configurations of [Ir2Si2] (or [Si2Ir2]) blocks, were examined. For these YIr2Si2 polymorphs, the optimized structural data, elastic parameters, electronic bands, total and partial densities of states, Fermi surface topology, and chemical bonding have been obtained and analyzed. Our studies showed that although ThCr2Si2- and CaBe2Ge2-type polymorphs are mechanically stable and relatively hard materials with low compressibility, they will behave as ductile systems. Among them, ThCr2Si2-type polymorph will show enhanced elastic anisotropy. In the vicinity of the Fermi energy, the topology of the electronic bands and the Fermi surface for various polymorphs are quite different. Besides, the CaBe2Ge2-type polymorph is expected to be anisotropic, i.e. happening mainly in the [Si2Ir2] blocks. The inter-atomic bonding for YIr2Si2 polymorph phases can be described as an anisotropic mixture of covalent, metallic, and ionic contributions, where inside the [Ir2Si2] (or [Si2Ir2]) blocks, Ir-Si and Ir-Ir bonds take place, whereas between the adjacent [Ir2Si2] (or [Si2Ir2]) blocks and Y atomic sheets, Si-Si and Ir-Y, Si-Ir and Si-Y, or mainly Ir-Ir bonds emerge for various polymorphs.

cond-mat.supr-con↗