Weak antilocalization in partially relaxed 200-nm HgTe films

TL;DR

This study investigates weak antilocalization effects in 200-nm HgTe films, revealing how surface-bulk carrier interactions influence magnetoresistance and WAL amplitude in a high-quality topological insulator with minimal bulk gap.

Contribution

It provides experimental insights into WAL behavior in HgTe films with reduced strain and zero bulk gap, highlighting the surface-bulk decoupling and its dependence on Fermi level and carrier density.

Findings

WAL correction is present across all Fermi levels.

Maximum WAL amplitude occurs near the bulk energy gap.

WAL amplitude decreases with increasing bulk carrier density.

Abstract

The anomalous magnetoresistance caused by the weak antilocalization (WAL) effects in 200-nm HgTe films is experimentally studied. The film is a high quality 3D topological insulator with much stronger spatial separation of surface states than in previously studied thinner HgTe structures. However, in contrast to that films, the system under study is characterized by a reduced partial strain resulting in an almost zero bulk energy gap. It has been shown that at all positions of the Fermi level the system exhibits a WAL conductivity correction superimposed on classical parabolic magnetoresistance. Since high mobility of carriers, the analysis of the obtained results was performed using a ballistic WAL theory. The maximum of the WAL conductivity correction amplitude was found at a Fermi level position near the bulk energy gap indicating to full decoupling of the surface carriers in these conditions. The WAL amplitude monotonously decreases when the density of either bulk electrons or holes increases that results from the increasing coupling between surface and bulk carriers.