Probing the semiconductor-to-dirac semimetal transition in Na-Sb-Bi alloys with x-ray Compton scattering

TL;DR

This study uses x-ray Compton scattering and first-principles modeling to investigate the electron redistribution during the transition from a semiconductor to a Dirac semimetal in Na-Sb-Bi alloys, revealing signatures and quantifying spin-orbit effects.

Contribution

It introduces a novel method to identify and quantify the semiconductor-to-Dirac semimetal transition using Compton profiles and electron counting, linking experimental and theoretical insights.

Findings

Signature of transition in Compton profile

Estimated electrons involved in transition

Deviation of Born charge of Na in Na3Bi

Abstract

We discuss electron redistribution during the semiconductor-to-Dirac semimetal transition in Na-Sb-Bi alloys using x-ray Compton scattering experiments combined with first-principles electronic structure modeling. A robust signature of the semiconductor-to-Dirac semimetal transition is identified in the spherically averaged Compton profile. We demonstrate how the number of electrons involved in this transition can be estimated to provide a novel descriptor for quantifying the strength of spin-orbit coupling responsible for driving the transition. The associated theoretical deviation of the Born charge of Na in Na$_3$Bi from the expected ionic charge of +1 is found to be consistent with the corresponding experimental value of about 10%. Our study also shows the sensitivity of the Compton scattering technique toward capturing the spillover of Bi 6p relativistic states onto Na sites.