Coexistence of bulk-nodal and surface-nodeless Cooper pairings in a superconducting Dirac semimetal

TL;DR

This study reveals the coexistence of nodal and nodeless superconducting gaps in a Dirac semimetal, PdTe, highlighting the interplay of topology, spin-orbit coupling, and superconductivity through detailed spectroscopic analysis.

Contribution

It provides the first detailed momentum-resolved evidence of both bulk nodal and surface nodeless superconducting gaps coexisting in a topological Dirac semimetal.

Findings

Surface state exhibits a fully gapped superconducting pairing below Tc.

Bulk shows a nodal superconducting gap near the Brillouin zone boundary.

Coexistence of nodeless and nodal gaps enforced by spin-orbit coupling.

Abstract

The interplay of nontrivial topology and superconductivity in condensed matter physics gives rise to exotic phenomena. However, materials are extremely rare where it is possible to explore the full details of the superconducting pairing. Here, we investigate the momentum dependence of the superconducting gap distribution in a novel Dirac material PdTe. Using high resolution, low temperature photoemission spectroscopy, we establish it as a spin-orbit coupled Dirac semimetal with the topological Fermi arc crossing the Fermi level on the (010) surface. This spin-textured surface state exhibits a fully gapped superconducting Cooper pairing structure below Tc~4.5K. Moreover, we find a node in the bulk near the Brillouin zone boundary, away from the topological Fermi arc.These observations not only demonstrate the band resolved electronic correlation between topological Fermi arc states and the way it induces Cooper pairing in PdTe, but also provide a rare case where surface and bulk states host a coexistence of nodeless and nodal gap structures enforced by spin-orbit coupling.