paper

Topological Surface States and Superconductivity in [Tl $_{4}$ ](Tl $_{1 - x}$ Sn $_{x}$ )Te $_{3}$ Perovskites

arXiv:1303.6350

Abstract

Materials with strong spin-orbit coupling have attracted attention following the prediction and subsequent discovery of strong two- and three-dimensional topological insulators in which a topological property of the bulk band structure of an insulator results in metallic surface states with Dirac-like dispersion. Here we report the discovery of Dirac-like surface states in the perovskite superconductor [Tl $_{4}$ ]TlTe $_{3}$ (Tl5Te3) and its non-superconducting tin-doped derivative, [Tl4](Tl $_{0.4}$ Sn $_{0.6}$ )Te $_{3}$ , as observed by angle-resolved photoemission spectroscopy (ARPES). Density functional theory (DFT) calculations predict a single spin-orbit driven band parity inversion at the $Z$ point above the Fermi level of Tl5Te3, suggesting the surface states are protected by Z $_{2}$ topology. Calculations on [Tl $_{4}$ ]SnTe $_{3}$ show no parity inversions, implying that a topological transition from non-trivial to trivial must occur upon doping with tin, i.e., [Tl $_{4}$ ](Tl $_{1 - x}$ Sn $_{x}$ )Te $_{3}$ . Thus [Tl $_{4}$ ]{\it M}Te $_{3}$ perovskites are a possible new, non-trigonal class of Z $_{2}$ topological compounds. Additionally, as Tl5Te3 is a stoichiometric bulk superconductor, these perovskites are ideal materials in which to study the interplay between surface states and bulk superconductivity.

Submitted to Nature Communications

Topological Surface States and Superconductivity in [Tl4​](Tl1−x​Snx​)Te3​ Perovskites

Abstract

Topological Surface States and Superconductivity in [Tl $_{4}$ ](Tl $_{1 - x}$ Sn $_{x}$ )Te $_{3}$ Perovskites