'Metal'-like transport in high-resistance, high aspect ratio two-dimensional electron gases

TL;DR

This study explores the unusual metallic-like transport in high-resistance, high aspect ratio 2D electron gases, showing that the phenomenon is not due to Coulomb blockade or percolation, but fits into the conventional 2D metal-insulator transition framework.

Contribution

The paper demonstrates that high-resistance, high aspect ratio 2DEGs exhibit metal-like transport without Coulomb blockade, supporting a 2D MIT interpretation.

Findings

No Coulomb blockade observed in high-resistance 2DEGs.

High-$ ho$, low-$T$ transport similar across geometries.

Magnetic field induces a metal-insulator transition.

Abstract

We investigate the striking absence of strong localisation observed in mesoscopic two-dimensional electron gases (2DEGs) (Baenninger et al 2008 Phys. Rev. Lett. 100 1016805, Backes et al 2015 Phys. Rev. B 92 235427) even when their resistivity $\rho >> h/e^2$. In particular, we try to understand whether this phenomenon originates in quantum many-body effects, or simply percolative transport through a network of electron puddles. To test the latter scenario, we measure the low temperature (low-$T$) transport properties of long and narrow 2DEG devices in which percolation effects should be heavily suppressed in favour of Coulomb blockade. Strikingly we find no indication of Coulomb blockade and that the high-$\rho$, low-$T$ transport is exactly similar to that previously reported in mesoscopic 2DEGs with different geometries. Remarkably, we are able to induce a `metal'-insulator transition (MIT) by applying a perpendicular magnetic field $B$. We present a picture within which these observations fit into the more conventional framework of the 2D MIT.