Landau Level Collapse in Gated Graphene Structures

TL;DR

This paper investigates a new magnetotransport regime in gated graphene, revealing a Landau level deconfinement transition through experimental measurements and semiclassical analysis, highlighting the collapse of SdH oscillations at a critical magnetic field.

Contribution

It introduces the concept of Landau level collapse in gated graphene structures and provides experimental and theoretical analysis of the transition from confined to deconfined electron trajectories.

Findings

Abrupt disappearance of SdH oscillations below a critical magnetic field.

Observation of Landau level deconfinement transition in gated graphene.

Semiclassical analysis explains the transition from closed to open cyclotron orbits.

Abstract

We describe a new regime of magnetotransport in two dimensional electron systems in the presence of a narrow potential barrier imposed by external gates. In such systems, the Landau level states, confined to the barrier region in strong magnetic fields, undergo a deconfinement transition as the field is lowered. We present transport measurements showing Shubnikov-de Haas (SdH) oscillations which, in the unipolar regime, abruptly disappear when the strength of the magnetic field is reduced below a certain critical value. This behavior is explained by a semiclassical analysis of the transformation of closed cyclotron orbits into open, deconfined trajectories. Comparison to SdH-type resonances in the local density of states is presented.