Three-dimensional Critical Dirac semimetal in KMgBi

TL;DR

This paper predicts that certain KMgBi compounds are symmetry-protected Dirac semimetals near phase boundaries, with potential to transition into Weyl semimetals or topological insulators through symmetry breaking.

Contribution

It introduces a new class of three-dimensional Dirac semimetals in KMgBi and explores their phase transitions driven by doping and symmetry breaking.

Findings

KMgBi compounds are symmetry-protected Dirac semimetals.

Doping Rb or Cs induces phase transitions between Dirac phases.

Breaking symmetries can turn these materials into Weyl semimetals or topological insulators.

Abstract

We predicted that AMgBi (A=K,Rb Cs), which have the same lattice structures as the 111 family of iron-based superconductors (Na/LiFeAs), are symmetry-protected Dirac semimetals located near the boundary of type-I and type-II Dirac semimetal phases. Doping Rb or Cs into KMgBi can drive the transition between the two phases. The materials can also be turned into Weyl semimetals and topological insulators by explicitly or spontaneously breaking time-reversal symmetry and C$_4$ lattice symmetry respectively.