Topological phase transition induced by random substitution

TL;DR

This study investigates how random chemical substitution induces a topological phase transition in a disordered alloy, revealing a transition point around x=0.5 with observable changes in electronic states and resistivity.

Contribution

It provides first-principles evidence of a topological phase transition driven by disorder in a zinc-blende alloy, highlighting the persistence of Dirac cones at strong disorder.

Findings

Phase transition occurs at x≈0.5 with well-defined Dirac cones.

Residual resistivity tensor confirms topologically trivial and nontrivial states.

Quantized off-diagonal spin-projected resistivity component observed.

Abstract

The transition from topologically nontrivial to a trivial state is studied by first-principles calculations on bulk zinc-blende type (Hg$_{1-x}$Zn$_x$)(Te$_{1-x}$S$_x$) disordered alloy series. The random chemical disorder was treated by means of the Coherent Potential Approximation. We found that although the phase transition occurs at the strongest disorder regime (${x\approx 0.5}$), it is still manifested by well-defined Bloch states forming a clear Dirac cone at the Fermi energy of the bulk disordered material. The computed residual resistivity tensor confirm the topologically-nontrivial state of the HgTe-rich (${x<0.5}$), and the trivial state of the ZnS-rich alloy series (${x>0.5}$) by exhibiting the quantized behavior of the off-diagonal spin-projected component, independently on the concentration $x$.