Exceptional Dirac states in a non-centrosymmetric superconductor, BiPd

TL;DR

This study uses high-resolution ARPES to accurately locate Dirac states in BiPd, clarifying their dimensionality and anisotropy, which are crucial for understanding topological superconductivity.

Contribution

The paper introduces a methodology with high-resolution ARPES to precisely identify Dirac nodes and reveals that their deviation from two-dimensionality is not an intrinsic material property.

Findings

Accurate localization of Dirac nodes in BiPd.

Revealed anisotropic topology of Dirac states.

Developed a model Hamiltonian explaining observed features.

Abstract

Quantum materials having Dirac fermions in conjunction with superconductivity is believed to be the candidate materials to realize exotic physics as well as advanced technology. Angle resolved photoemission spectroscopy (ARPES), a direct probe of the electronic structure, has been extensively used to study these materials. However, experiments often exhibit conflicting results on dimensionality and momentum of the Dirac Fermions (e.g. Dirac states in BiPd, a novel non-centrosymmetric superconductor), which is crucial for the determination of the symmetry, time-reversal invariant momenta and other emerging properties. Employing high-resolution ARPES at varied conditions, we demonstrated a methodology to identify the location of the Dirac node accurately and discover that the deviation from two-dimensionality of the Dirac states in BiPd proposed earlier is not a material property. These results helped to reveal the topology of the anisotropy of the Dirac states accurately. We have constructed a model Hamiltonian considering higher-order spin-orbit terms and demonstrate that this model provides an excellent description of the observed anisotropy. Intriguing features of the Dirac states in a non-centrosymmetric superconductor revealed in this study expected to have significant implication in the properties of topological superconductors.