Observation of topological surface state in a superconducting material

TL;DR

This paper reports the discovery of topological surface states in the superconducting material CaBi2, combining ARPES experiments, calculations, and transport measurements to suggest it as a platform for studying superconductivity and topology interplay.

Contribution

It provides the first evidence of topological surface states in CaBi2, a superconductor, through ARPES and theoretical analysis, highlighting its potential for topological superconductor research.

Findings

Presence of Dirac cones with topological protection

Weak topological indices identified in CaBi2

Large magnetoresistance observed in transport measurements

Abstract

The discovery of topological insulator phase has ignited massive research interests in novel quantum materials. Topological insulators with superconductivity further invigorate the importance of materials providing the platform to study the interplay between these two unique states. However, the candidates of such materials are rare. Here, we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of a superconducting material CaBi2 [Tc = 2 K], corroborated by the first principles calculations. Our study reveals the presence of Dirac cones with a topological protection in this system. Systematic topological analysis based on symmetry indicator shows the presence of weak topological indices in this material. Furthermore, our transport measurements show the presence of large magnetoresistance in this compound. Our results indicate that CaBi2 could potentially provide a material platform to study the interplay between superconductivity and topology.