Coexistence of near-EF van Hove singularity and in-gap topological Dirac surface states in superconducting electrides

TL;DR

This study reveals that La3In exhibits a unique combination of a near-EF van Hove singularity and in-gap topological Dirac surface states, making it a promising candidate for topological superconductivity exploration.

Contribution

It provides the first detailed electronic structure analysis of La3In, highlighting the coexistence of van Hove singularity and topological surface states at ambient pressure.

Findings

Observation of a saddle point at the BZ boundary

Detection of a three-dimensional van Hove singularity crossing EF

Identification of topological Dirac surface states within the bulk gap

Abstract

Superconducting electrides have attracted growing attention for their potential to achieve high superconducting transition temperatures (TC) under pressure. However, many known electrides are chemically reactive and unstable, making high-quality single-crystal growth, characterization, and measurements difficult, and most do not exhibit superconductivity at ambient pressure. In contrast, La3In stands out for its ambient-pressure superconductivity (TC ~ 9.4 K) and the availability of high-quality single crystals. Here, we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations. The bands near the Fermi energy are mainly derived from La 5d and In 5p orbitals. A saddle point is directly observed at the Brillouin zone (BZ) boundary, while a three-dimensional van Hove singularity crosses EF at the BZ corner. First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above EF. The coexistence of a high density of states and in-gap topological surface states near EF suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.