Superconducting Dome and Crossover to an Insulating State in [Tl4]Tl1-xSnxTe3

TL;DR

This study explores the phase diagram of [Tl4]Tl1-xSnxTe3, revealing a superconducting dome for certain compositions and a transition from metallic to insulating states linked to topological phase changes.

Contribution

It provides the first comprehensive phase diagram combining experimental and theoretical insights into superconductivity and topological states in [Tl4]Tl1-xSnxTe3.

Findings

Superconductivity exists for 0 < x < 0.4.

A crossover from metallic to insulating behavior occurs at x = 1.

x=0 is a topological metal; x=1 is a topological crystalline insulator.

Abstract

The structural, superconducting, and electronic phase diagram of [Tl4]Tl1-xSnxTe3 is reported. Magnetization and specific heat measurements show bulk superconductivity exists for 0 < x < 0.4. Resistivity measurements indicate a crossover from a metallic state for low dopings to a doped insulator at x = 1. Universally, there is a large non-Debye specific heat contribution, characterized by an Einstein temperature of {\theta}E ~ 35 K. Density functional theory calculations predict x = 0 to be a topological metal, while x = 1 is a topological crystalline insulator. The disappearance of superconductivity correlates with the transition between these distinct topological states.