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 h/e2. In this case, transport at sufficiently low temperatures, T1 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 T is in good agreement with measurements of T in 2D electron layers in gated mesoscopic GaAs/AlGaAs structures and, in particular, T can even exhibit an anomalous metalliclike drop as T→0 even for resistivities as high as 500h/e2

Unconventional metallicity and giant thermopower in a strongly interacting two-dimensional electron system

“…13, that at low n s values, where the 2DES is expected to be localized, ρ 2DES (T ) does not diverge as T → 0 but saturates at values h/e 2 below ≈ 0.8 K, indicating noninsulating behavior. The precise mechanism for resistivity saturation is debated, ranging from quantum tunneling between multiple electron puddles 21,22 to defect migration in a spontaneously broken symmetry phase. 13,14 Figure 4(b) shows S as a function of T at the same n s as Fig.…”

Colossal nonsaturating linear magnetoresistance in two-dimensional electron systems at a GaAs/(Al,Ga)As heterointerface

“…1(b)] with a correlation length of ∼2d. [12][13][14] In this regime, the 2DES disintegrates into small puddles of charge that often manifest in Coulomb blockade effects in mesoscopic devices. 11,13,15 In essence, this increase in inhomogeneity arises due to the weakening of electrostatic screening of the background disorder potential landscape, causing the spatial fluctuations in carrier density to be of the same order as the carrier density itself.…”