Dirac semimetal and topological phase transitions in A3Bi (A=Na, K, Rb)

TL;DR

This paper demonstrates that A3Bi compounds (A=Na, K, Rb) are stable 3D Dirac semimetals with protected Dirac points, surface Fermi arcs, and can transition into different topological phases upon symmetry breaking, exhibiting notable quantum phenomena.

Contribution

It reveals that A3Bi compounds are stable Dirac semimetals with symmetry-protected Dirac points and surface states, and explores their topological phase transitions and quantum properties.

Findings

A3Bi compounds are Dirac semimetals with protected bulk Dirac points.

Surface Fermi arcs are observed in these materials.

They can undergo topological phase transitions when symmetries are broken.

Abstract

The three-dimensional (3D) Dirac point, where two Weyl points overlap in momentum space, is usually unstable and hard to realize. Here we show, based on the first-principles calculations and effective model analysis, that crystalline $A_3$Bi ($A$=Na, K, Rb) are Dirac semimetals with bulk 3D Dirac points protected by crystal symmetry. They possess non-trivial Fermi arcs on the surfaces, and can be driven into various topologically distinct phases by explicit breaking of symmetries. Giant diamagnetism, linear quantum magnetoresistance, and quantum spin-Hall effect will be expected for such compounds.