Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi₃ (A = Sr and Ba).

D F Shao,W J Lu,X D Zhu,L Hu,X Luo,X B Zhu,Y P Sun,W H Song

doi:10.1038/srep21484

D F Shao, W J Lu + Show 6 more

Open Access

https://doi.org/10.1038/srep21484

Copy DOI

Abstract

Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

Highlights

Materials with strong spin-orbit coupling (SOC) effect have attracted a great deal of attention due to the resulted novel topological phases
We figured out the role of SOC in ABi3 (A = Sr and Bi) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling
Our investigation demonstrates that superconductivity in Bi-rich compounds ABi3 (A = Sr and Bi) is strongly enhanced by SOC, which is due to the SOC induced softening, and the SOC related increase of electron-phonon coupling matrix elements

Summary

Introduction

Materials with strong spin-orbit coupling (SOC) effect have attracted a great deal of attention due to the resulted novel topological phases. Among those materials, the heaviest group V semimetal Bi-based compounds are mostly investigated[1]. First principle calculation without including SOC estimated a superconducting transition temperature (Tc) of 1.8 K for SrBi317, which is remarkably smaller than the experimentally measured Tc of ~5.6 K15,16. Such large deviation was attributed to the disadvantage of the calculation method[17]. Fermi surface nesting exists between the electron-pockets at the face centers, which leads to phonon instabilities

Methods

Results

Conclusion