Superconductivity, valence-skipping and topological crystalline metal in AgSnSe${}_2$

Abstract

The recent suggestion of valence-skipping phenomenon driving a two-gap superconductivity in $Ag$-doped SnSe, by Kataria, \textit{et al.} [Phys. Rev. B 107, 174517 (2023)], has brought to the fore a long-standing issue once again. The absence of crystallographically inequivalent Sn cites corroborated by electronic properties of AgSnSe${}_2$, calculated using first-principles density functional theory, however, does not appear to provide a strong support in favor of valence-skipping in this system. Interestingly, the signature of avoided band-crossings (with the inclusion of SOC) and non-zero \textit{mirror} Chern number ($n_{\mathcal{M}}$) confirm a non-trivial topology. The presence of mirror symmetry-protected surface states along the mirror planes indicates that AgSnSe${}_2$ could be a potential candidate for topological crystalline metals (TCMs). Moreover, our calculation of electron-phonon coupling and anisotropic superconducting properties of AgSnSe${}_2$, using Migdal-Eliashberg theory, gives a single-gap superconductivity with critical temperature $T_c\approx 7$K, consistent with the experimental value of $5$K. The interplay of topology and superconductivity in this three-dimensional material appears quite intriguing and it may provide new insights into the exploration of superconductivity and topology.

arXiv comment9 pages including references, and 7 figures

References in corpus (35)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Berry Phase Effects on Electronic Properties
• Maximally-localized generalized Wannier functions for composite energy bands
• Wannier90: A Tool for Obtaining Maximally-Localised Wannier Functions
• WannierTools: An open-source software package for novel topological materials
• Maximally-localized Wannier functions for entangled energy bands
• Topological Crystalline Insulators
• Quantum ESPRESSO toward the exascale
• Topological Crystalline Insulators in the SnTe Material Class
• EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions
• Experimental realization of a topological crystalline insulator in SnTe
• Surface States of the Topological Insulator Bi_{1-x}Sb_x
• A topological crystalline insulator (TCI) phase via topological phase transition and crystalline mirror symmetry
• Topological Insulators and Nematic Phases from Spontaneous Symmetry Breaking in 2D Fermi Systems with a Quadratic Band Crossing
• Anisotropic Migdal-Eliashberg theory using Wannier functions
• Surface States of Topological Crystalline Insulators in IV-VI Semiconductors
• Electronic structure and thermoelectric properties of n- and p-type SnSe from first principles calculations
• Effective theory of quadratic degeneracies
• Rock-salt SnS and SnSe: Native Topological Crystalline Insulators
• Berry-phase description of Topological Crystalline Insulators
• Superconductivity in charge Kondo systems
• Pressure-induced Topological Phase Transitions in Rock-salt Chalcogenides
• Non-trivial spin-texture of the coaxial Dirac cones on the surface of topological crystalline insulator SnTe
• Band structure of a IV-VI black phosphorus analogue, the thermoelectric SnSe
• Surface States of Perovskite Iridates AIrO${}_3$; Signatures of Topological Crystalline Metal with Nontrivial ${\mathbb{Z}}_2$ Index
• Quantum Spin Hall Effect in IV-VI Topological Crystalline Insulators
• Electrically Tunable Quantum Spin Hall State in Topological Crystalline Insulator Thin films
• Anomalous metallic state above the upper critical field of the conventional three-dimensional superconductor AgSnSe2 with strong intrinsic disorder
• Topological superconductivity and Majorana bound states at the LaAlO${}_3$/SrTiO${}_3$ interface
• The Exotic Barium Bismuthates
• Observation of oscillatory relaxation in the Sn-terminated surface of epitaxial rock-salt SnSe $\{111\}$ topological crystalline insulator
• Efficient anisotropic Migdal-Eliashberg calculations with the Intermediate Representation basis and Wannier interpolation
• Electron-phonon coupling, critical temperatures and gaps in $\mathrm{NbS}{\mathrm{e}}_2$/$\mathrm{Mo}{\mathrm{S}}_2$ Ising Superconductors
• Superconducting ground state study of valence skip compound AgSnSe${}_2$