Topological Dirac States and Pairing Correlations in the Non-Centrosymmetric Superconductor PbTaSe2

TL;DR

This paper demonstrates that PbTaSe2 is a non-centrosymmetric superconductor with topologically nontrivial Dirac states, combining first-principles calculations, ARPES experiments, and theoretical analysis to reveal its potential for novel topological superconductivity.

Contribution

It provides the first comprehensive study showing PbTaSe2's nontrivial Z2 topological invariant and Dirac states, linking phonon spectrum analysis to its superconducting properties.

Findings

PbTaSe2 has a nonzero Z2 topological invariant.

It possesses fully spin-polarized Dirac states.

Superconductivity emerges due to phonon stiffening from Pb intercalation.

Abstract

Superconductivity in topological band structures is a platform for many novel exotic quantum phenomena such as emergent supersymmetry. This potential nourishes the search for topological materials with intrinsic superconducting instabilities, in which Cooper pairing is introduced to electrons with helical spin texture such as the Dirac states of topological insulators and Dirac Semimetals, forming a natural topological superconductor of helical kind. We employ first-principles calculations, ARPES experiments and new theoretical analysis to reveal that PbTaSe2, a non-centrosymmetric superconductor, possesses a nonzero Z2 topological invariant and fully spin-polarized Dirac states. Moreover, we analyze the phonon spectrum of PbTaSe2 to show how superconductivity can emerge due to a stiffening of phonons by the Pb intercalation, which diminishes a competing charge-density-wave instability. Our work establishes PbTaSe2 as a stoichiometric superconductor with nontrivial Z2 topological band structure, and shows that it holds great promise for studying novel forms of topological superconductivity not realized previously.