Topologically nontrivial electronic states in CaSn$_{3}$

TL;DR

This paper predicts topologically non-trivial electronic states in the superconducting material CaSn₃ using first-principles calculations, revealing nodal-line semimetal states, Weyl nodes, and unique Fermi arc surface states.

Contribution

It is the first theoretical proposal of topological states in CaSn₃, linking topological physics with superconductivity in this material.

Findings

CaSn₃ hosts 3D topological nodal-line semimetal states without SOC.

Inclusion of SOC transforms nodal lines into Weyl nodes with Berry flux.

Unique closed-loop Fermi arc surface states are identified.

Abstract

Based on the first-principles calculations, we theoretically propose topologically non-trivial states in a recently experimentally discovered superconducting material CaSn$_3$. When the spin-orbit coupling (SOC) is ignored, the material is a host to three-dimensional topological nodal-line semimetal states. Drumhead like surface states protected by the coexistence of time-reversal and mirror symmetry emerge within the two-dimensional regions of the surface Brillouin zone connecting the nodal lines. When SOC is included, unexpectedly, each nodal line evolves into two Weyl nodes (W1, W2) in this centrosymmetric material. Berry curvature calculations show that these nodes occur in a pair and act as either a source or sink of Berry flux. The material also has unique surface states in the form of Fermi arcs, which unlike other known Weyl semimetal, form closed loops of surface states on the Fermi surface. Our theoretical realization of topologically non-trivial states in a superconducting material paves the way towards unraveling the interconnection between topological physics and superconductivity.