Pressure Induced Topological Superconductivity in the Spin-Orbit Mott Insulator GaTa4Se8

TL;DR

This paper demonstrates that pressure induces a topological superconducting phase in GaTa4Se8, characterized by spin-2 Cooper pairs and novel surface states, revealing new possibilities for exotic superconductivity in spin-orbit materials.

Contribution

The study uncovers a pressure-induced topological superconducting phase with spin-2 pairing in GaTa4Se8, combining first-principles calculations and proposing experimental verification methods.

Findings

Pressure induces topological superconductivity in GaTa4Se8.

Stabilization of a d-wave quintet pairing channel under pressure.

Surface states exhibit novel topological properties.

Abstract

Lacunar spinel GaTa$_4$Se$_8$ is a unique example of spin-orbit coupled Mott insulator described by molecular $j_{\text{eff}}\!=\!3/2$ states. It becomes superconducting at T$_c$=5.8K under pressure without doping. In this work, we show, this pressure-induced superconductivity is a realization of a new type topological phase characterized by spin-2 Cooper pairs. Starting from first-principles density functional calculations and random phase approximation, we construct the microscopic model and perform the detailed analysis. Applying pressure is found to trigger the virtual interband tunneling processes assisted by strong Hund coupling, thereby stabilizing a particular $d$-wave quintet channel. Furthermore, we show that its Bogoliubov quasiparticles and their surface states exhibit novel topological nature. To verify our theory, we propose unique experimental signatures that can be measured by Josephson junction transport and scanning tunneling microscope. Our findings open up new directions searching for exotic superconductivity in spin-orbit coupled materials.