Conductance Fluctuations Near the Two-Dimensional Metal-Insulator Transition

TL;DR

This study investigates conductance fluctuations and the metal-insulator transition in high-mobility Si-MOSFETs, revealing non-monotonic fluctuation scales and supporting Coulomb interactions as the transition driver.

Contribution

It provides new insights into conductance fluctuations near the 2D MIT, highlighting non-monotonic fluctuation scales and their relation to Coulomb interactions.

Findings

Identification of multiple fluctuation scales near the MIT

Non-monotonic variation of fluctuation scales with gate voltage

Support for Coulomb interactions driving the MIT

Abstract

Measurements of conductance $G$ on short, wide, high-mobility Si-MOSFETs reveal both a two-dimensional metal-insulator transition (MIT) at moderate temperatures (1 $<~ T <$ 4~K) and mesoscopic fluctuations of the conductance at low temperatures ($T~ <$ 1~K). Both were studied as a function of chemical potential (carrier concentration $n_s$) controlled by gate voltage ($V_g$) and magnetic field $B$ near the MIT. Fourier analysis of the low temperature fluctuations reveals several fluctuation scales in $V_g$ that vary non-monotonically near the MIT. At higher temperatures, $G(V_g,B)$ is similar to large FETs and exhibits a MIT. All of the observations support the suggestion that the MIT is driven by Coulomb interactions among the carriers.