Topological tuning in three-dimensional Dirac semimetals

TL;DR

This paper investigates how changing composition in certain three-dimensional Dirac semimetals induces a topological phase transition from a Dirac semimetal to a trivial insulator, affecting bulk and surface states.

Contribution

It demonstrates a compositional tuning method to control topological phases and Dirac point positions in specific alloyed Dirac semimetals using first-principles calculations.

Findings

Identified topological phase transition in Na3Bi1-xSbx and Cd3[As1-xPx]2 alloys.

Showed composition-dependent shift of Dirac points in reciprocal space.

Revealed band inversion reversal at the phase transition.

Abstract

We study with first-principles methods the interplay between bulk and surface Dirac fermions in three dimensional Dirac semimetals. By combining density functional theory with the coherent potential approximation, we reveal a topological phase transition in Na$_3$Bi$_{1-x}$Sb$_{x}$ and Cd$_3$[As$_{1-x}$P$_x$]$_2$ alloys, where the material goes from a Dirac semimetal to a trivial insulator upon changing Sb or P concentrations. Tuning the composition allows us to engineer the position of the bulk Dirac points in reciprocal space. Interestingly, the phase transition coincides with the reversal of the band ordering between the conduction and valence bands.