Anomalous transport in mesoscopic inhomogeneous two-dimensional electron systems at low temperature

Abstract

We analyze transport properties of mesoscopic GaAs two-dimensional (2D) electron systems in the insulating regime. It is well known that disorder can cause the insulating system to break up into connected insulating domains and isolated conducting domains. In mesoscopic systems the separation between conducting domains can be very small even when $\ensuremath{\rho}⪢h/{e}^{2}$. In this case, transport at sufficiently low temperatures, $T\ensuremath{\lesssim}1\text{ }\text{K}$, is controlled not by conventional hopping but by short-range tunneling between adjacent conducting domains, and this has a dramatic effect on the low-$T$ transport properties. The resulting $T$-dependent resistivity $\ensuremath{\rho}(T)$ is in good agreement with measurements of $\ensuremath{\rho}(T)$ in 2D electron layers in gated mesoscopic GaAs/AlGaAs structures and, in particular, $\ensuremath{\rho}(T)$ can even exhibit an anomalous metalliclike drop as $T\ensuremath{\rightarrow}0$ even for resistivities $\ensuremath{\rho}$ as high as $\ensuremath{\sim}500h/{e}^{2}$.