Nontrivial topological states in BaSn5 superconductor probed by de Haas-van Alphen quantum oscillations

TL;DR

This study uncovers nontrivial topological states in the superconductor BaSn5 through experimental measurements and first-principles calculations, revealing topological nodal rings and Dirac points that coexist with superconductivity.

Contribution

It demonstrates the presence of topological nodal rings and Dirac points in BaSn5, linking topological states with superconductivity through combined experimental and theoretical analysis.

Findings

Identification of topological nodal ring at H point in BZ

Detection of Dirac points above Fermi level due to SOC

Observation of nontrivial Berry phase in quantum oscillations

Abstract

We report herein the nontrivial topological states in an intrinsic type-II superconductor BaSn5 (Tc ~ 4.4 K) probed via measuring the magnetizations, specific heat, de Haas-van Alphen (dHvA) effect and performing first principles calculations. The first principles calculations reveal a topological nodal ring structure centering at the H point in the kz = {\pi} plane of the Brillouin zone (BZ), which could be gapped by spin-orbit coupling (SOC), yielding rather small gaps below and above the Fermi level about 0.04 eV and 0.14 eV, respectively. The SOC also results in a pair of Dirac points along the {\Gamma}-A direction and located ~ 0.2 eV above the Fermi level. The analysis of the dHvA quantum oscillations supports the calculations by revealing nontrivial Berry phase originated from three hole and one electron pockets related to the bands forming the Dirac cones. Our study thus provides an excellent avenue for investigating the interplay between superconductivity and nontrivial topological states.