Coexistence of nontrivial topological properties and strong ferromagnetic fluctuations in quasi-one-dimensional A2Cr3As3

Chenchao Xu,Bing-Hua Lei,Ninghua Wu,Xu Duan,Chao Cao,Guo-Xiang Zhi,Qijin Chen,Fanlong Ning

doi:10.1038/s41524-020-0294-9

Abstract

Superconductivity in crystals without inversion symmetry has received extensive attention due to its unconventional pairing and possible nontrivial topological properties. Using first-principles calculations, we systemically study the electronic structure of noncentrosymmetric superconductors A2Cr3As3 (A = Na, K, Rb, and Cs). Topologically protected triply degenerate points connected by one-dimensional arcs appear along the C3 axis, coexisting with strong ferromagnetic (FM) fluctuations in the non-superconducting state. Within random phase approximation, our calculations show that strong enhancements of spin fluctuations are present in K2Cr3As3 and Rb2Cr3As3 and are substantially reduced in Na2Cr3As3 and Cs2Cr3As3. Symmetry analysis of pairing gap Δ(k) and spin–orbit coupling gk suggest that the arc surface states may also exist in the superconducting state, giving rise to possible nontrivial topological properties.

Highlights

Materials with nontrivial topological properties have been extensively studied over the past two decades
Since the discovery of Weyl, Dirac, nodal line semimetals, and triply degenerate point (TP) topological metals[4,5,6,7,8,9,10,11,12,13,14,15], it was shown that gapless systems can possess novel topology as well
The TP topological metal has been regarded as the intermediate phase between Dirac and Weyl semimetals[14]

Summary

INTRODUCTION

Materials with nontrivial topological properties have been extensively studied over the past two decades. Since the discovery of Weyl, Dirac, nodal line semimetals, and triply degenerate point (TP) topological metals[4,5,6,7,8,9,10,11,12,13,14,15], it was shown that gapless systems can possess novel topology as well It is possible for superconductors with nodes (e.g., CePt3Si, UPt3) to have topologically protected edge states, which are guaranteed by momentumdependent topological numbers[16,17,18]. We discuss the possibility of the existence of topologically stable arc states in the superconducting phase

Xu et al 2

DISCUSSION

METHODS

CODE AVAILABILITY