Spectrum of an open disordered quasi-two-dimensional electron system: strong orbital effect of the weak in-plane magnetic field

TL;DR

This paper investigates how a weak in-plane magnetic field significantly alters the mode spectrum and density of states in open disordered quasi-two-dimensional electron systems, leading to a metal-insulator transition.

Contribution

It reveals that even a weak in-plane magnetic field can drastically reduce the number of conducting modes and induce a singularity in the density of states, explaining the metal-insulator transition.

Findings

Weak magnetic fields cut off extended modes from the spectrum.

Reduction of current-carrying modes correlates with metal-insulator transition.

Mode dephasing due to disorder dominates magnetic field effects.

Abstract

The effect of an in-plane magnetic field upon open quasi-two-dimensional electron and hole systems is investigated in terms of the carrier ground-state spectrum. The magnetic field, classified as weak from the viewpoint of correlation between size parameters of classical electron motion and the gate potential spatial profile is shown to efficiently cut off extended modes from the spectrum and to change singularly the mode density of states (MDOS). The reduction in the number of current-carrying modes, right up to zero in magnetic fields of moderate strength, can be viewed as the cause of magnetic-field-driven metal-to-insulator transition widely observed in two-dimensional systems. Both the mode number reduction and the MDOS singularity appear to be most pronounced in the mode states dephasing associated with their scattering by quenched-disorder potential. This sort of dephasing is proven to dominate the dephasing which involves solely the magnetic field whatever level of the disorder.