Coexistence of near-E_F Van Hove Singularity and in-Gap Topological Dirac Surface States in Superconducting Electrides

Abstract Superconducting electrides have attracted growing attention for their potential to achieve high superconducting transition temperatures (T_C) 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 (T_C ∼ 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 (E_F) 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 E_F at the BZ corner. First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_F. The coexistence of a high density of states and in-gap topological surface states near E_F suggests that La₃In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.