Finite Conductivity in Mesoscopic Hall Bars of Inverted InAs/GaSb Quantum Wells

TL;DR

This study investigates the low temperature electrical conductivity of mesoscopic InAs/GaSb quantum well Hall bars, revealing residual conductivity within the hybridization gap and discussing implications for helical edge state stability.

Contribution

It provides experimental evidence of residual conductivity in the hybridization gap of InAs/GaSb quantum wells and analyzes its origin considering impurity scattering effects.

Findings

Residual conductivity observed in the hybridization gap.

Conductivity explained by contributions from free and hybridized carriers.

Implications for the stability of helical edge states discussed.

Abstract

We have studied experimentally the low temperature conductivity of mesoscopic size InAs/GaSb quantum well Hall bar devices in the inverted regime. Using a pair of electrostatic gates we were able to move the Fermi level into the electron-hole hybridization state, and observe a mini gap. Temperature dependence of the conductivity in the gap shows residual conductivity, which can be consistently explained by the contributions from the free as well as the hybridized carriers in the presence of impurity scattering, as proposed by Naveh and Laikhtman [Euro. Phys. Lett., 55, 545-551 (2001)]. Experimental implications for the stability of proposed helical edge states will be discussed.