Quantum transport and mobility spectrum of topological carriers in (001) SnTe/PbTe heterojunctions

TL;DR

This study investigates the quantum transport properties and mobility spectra of topological states in SnTe/PbTe heterojunctions, revealing the presence of gapped and gapless Dirac cones and demonstrating the application of mobility spectrum analysis to topological materials.

Contribution

The paper provides experimental evidence of topological states in SnTe/PbTe heterojunctions and introduces a classical model-based mobility spectrum analysis method for such systems.

Findings

Quantum corrections suggest topological states at the junction interface.

Presence of gapped midgap states in 5 nm SnTe layer.

Gapless Dirac cones explain phase coherence effects in thicker samples.

Abstract

Measurements of magnetotransport in SnTe/PbTe heterojunctions grown by the MBE technique on (001) undoped CdTe substrates were performed. At low magnetic fields, quantum corrections to conductivity were observed that may be attributed to the presence of topological states at the junction interface. For a sample with 5 nm thick SnTe layer, the data analysis suggests that midgap states are actually gapped. However, the phase coherence effects in 10 nm and 20 nm SnTe/PbTe samples are fully explained assuming existence of gapless Dirac cones. Magnetotransport at higher magnetic fields is described in the framework of mobility spectrum analysis (MSA). We demonstrate that the electron- and hole-like peaks observed simultaneously for all SnTe/PbTe heterojunctions may originate from the concave and convex parts of the energy isosurface for topological states -- and not from the existence of quasiparticles both carrying negative and positive charges. This interpretation is supported by numerical calculations of conductivity tensor components for gapless (100) Dirac cones, performed within a classical model and based on the solutions of Boltzmann transport equation. Our approach shows the feasibility of MSA in application to magnetotransport measurements on topological matter.