Local imaging of high mobility two-dimensional electron systems with virtual scanning tunneling microscopy

TL;DR

This paper introduces a novel 'virtual scanning tunneling microscopy' technique enabling local tunneling into high mobility 2DESs with sub-200 nm resolution, facilitating direct spatial mapping of complex electron states.

Contribution

The paper presents a new method for local imaging of high mobility 2DESs using a bilayer heterostructure and scanning gate, overcoming previous resolution limitations.

Findings

Achieved sub-200 nm control of local tunneling into 2DES.

Demonstrated feasibility of spatially mapping electron states.

Developed a tunable bilayer heterostructure for imaging.

Abstract

Correlated electron states in high mobility two-dimensional electron systems (2DESs), including charge density waves and microemulsion phases intermediate between a Fermi liquid and Wigner crystal, are predicted to exhibit complex local charge order. Existing experimental studies, however, have mainly probed these systems at micron to millimeter scales rather than directly mapping spatial organization. Scanning probes should be well-suited to study the spatial structure of these states, but high mobility 2DESs are found at buried semiconductor interfaces, beyond the reach of conventional scanning tunneling microscopy. Scanning techniques based on electrostatic coupling to the 2DES deliver important insights, but generally with resolution limited by the depth of the 2DES. In this Letter, we present our progress in developing a technique called "virtual scanning tunneling microscopy" that allows local tunneling into a high mobility 2DES. Using a specially-designed bilayer GaAs/AlGaAs heterostructure where the tunnel coupling between two separate 2DESs is tunable via electrostatic gating, combined with a scanning gate, we show that the local tunneling can be controlled with sub-200 nm resolution.