Observation of Dirac-like energy band and unusual spectral line shape in quasi-one-dimensional superconductor Tl2Mo6Se6

TL;DR

This study uses high-resolution photoemission spectroscopy to reveal a Dirac-like energy band and unconventional superconducting features in the quasi-one-dimensional superconductor Tl2Mo6Se6, suggesting topological superconductivity.

Contribution

It provides the first direct observation of a Dirac-like band and unusual spectral line shape in Tl2Mo6Se6, linking its electronic structure to potential topological superconductivity.

Findings

Observation of a quasi-1D Dirac-like energy band.

Detection of a superconducting gap signature below Tc.

Significant spectral-weight reduction indicating unconventional superconductivity.

Abstract

We have performed high-resolution angle-resolved photoemission spectroscopy of the quasi-one-dimensional (1D) topological superconductor candidate Tl2Mo6Se6 consisting of weakly-coupled Mo3Se3 chains. We found a quasi-1D Fermi surface arising from a Dirac-like energy band, which is associated with the nonsymmorphic screw symmetry of the chains and predicted to trigger topological superconductivity. We observed a significant spectral-weight reduction over a wide energy range, together with a tiny Fermi-edge structure which exhibits a signature of a superconducting-gap opening below the superconducting-transition temperature. The observed quasi-1D Dirac-like band and its very small density of states point to an unconventional nature of superconductivity in Tl2Mo6Se6.