Dirac parameters and topological phase diagram of Pb1-xSnxSe from magneto-spectroscopy

TL;DR

This study comprehensively maps the band structure parameters of Pb1-xSnxSe across composition and temperature, revealing insights into its topological phase transition and the behavior of 3D Dirac fermions.

Contribution

It provides the first detailed experimental mapping of the 3D band structure parameters of Pb1-xSnxSe near the topological phase transition.

Findings

Non-closure of the energy gap near the phase transition

Determination of Dirac velocity and anisotropy factor

Evidence of Pb1-xSnxSe as a model system for topological phases

Abstract

Pb1-xSnxSe hosts 3D massive Dirac fermions across the entire composition range for which the crystal structure is cubic. In this work, we present a comprehensive experimental mapping of the 3D band structure parameters of Pb1-xSnxSe as a function of composition and temperature. We cover a parameter space spanning the band inversion that yields its topological crystalline insulator phase. A non-closure of the energy gap is evidenced in the vicinity of this phase transition. Using magnetooptical Landau level spectroscopy, we determine the energy gap, Dirac velocity, anisotropy factor and topological character of Pb1-xSnxSe epilayers grown by molecular beam epitaxy on BaF2 (111). Our results are evidence that Pb1-xSnxSe is a model system to study topological phases and the nature of the phase transition.