Theoretical study of dynamical and electronic properties of noncentrosymmetric superconductor NbReSi

TL;DR

This theoretical study uses ab initio methods to determine the stable symmetry and electronic properties of the NbReSi superconductor, clarifying its phonon and surface state characteristics.

Contribution

The paper identifies Par{6}2m as the stable symmetry of NbReSi and analyzes its dynamical and electronic properties using first-principles calculations.

Findings

Ima2 symmetry is unstable for NbReSi.

Par{6}2m symmetry remains stable under pressure.

NbReSi hosts phonon surface states for specific surfaces.

Abstract

The noncentrosymmetric NbReSi superconductor with $T_{c} \simeq 6.5$ K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested realization of P$\bar{6}$2m or Ima2 symmetry. We discuss the dynamical properties of both symmetries (e.g., phonon spectra). In this paper, using the ab initio techniques, we clarify this ambiguity, and conclude that the Ima2 symmetry is unstable, and P$\bar{6}$2m should be realized. The P$\bar{6}$2m symmetry is also stable in the presence of external hydrostatic pressure. We show that NbReSi with the P$\bar{6}$2m symmetry should host phonon surface states for (100) and (110) surfaces. Additionally, we discuss the main electronic properties of the system with the stable symmetry.