Simultaneous Superconducting and Topological Properties in Mg-Li Electrides at High Pressures

TL;DR

This study predicts and characterizes novel Mg-Li electride phases under high pressure that exhibit superconductivity, topological surface states, and electride properties, revealing the coexistence of multiple quantum phenomena in a single material.

Contribution

It introduces new stable Mg-Li electride phases with superconducting and topological features, advancing understanding of multi-quantum phases in electrides under extreme conditions.

Findings

MgLi10 is a semiconductor with a 0.22 eV band gap.

Pm-3m MgLi is a superconductor with Tc of 22.8 K.

Pm-3m MgLi and Pnma MgLi exhibit topological surface states and non-zero Z2 invariant.

Abstract

Electrides as a unique class of emerging materials exhibit fascinating properties and hold important significance for understanding the matter under extreme conditions, which is characterized by valence electrons localized into the interstitial space as quasi-atoms (ISQs). In this work, using crystal structure prediction and first-principles calculations, we identified seven stable phases of Mg-Li that are electride with novel electronic properties under high pressure. Among them, MgLi10 is a semiconductor with a band gap of 0.22 eV; and Pm-3m MgLi is superconductor with a superconducting transition temperature of 22.8 K. The important role played by the localization degree of ISQ in the superconducting transition temperature of these electrides is revealed by systematic comparison of Mg-Li with other Li-rich electride superconductors. Furthermore, we proved that Pm-3m MgLi and Pnma MgLi also have distinct topological behavior with metallic surface states and the non-zero $Z_2$ invariant. The simultaneous coexistence of superconductivity, electronic band topology and electride property in the same structure of Pm-3m MgLi and Pnma MgLi demonstrates the feasibility of realizing multi-quantum phases in a single material, which will stimulate further research in these interdisciplinary fields.