Acousto-electric study of microwave-induced current domains

TL;DR

This study uses Surface Acoustic Waves to probe bulk electronic properties and domain formation in a 2D electron system under microwave radiation, revealing inhomogeneous phases during zero-resistance states.

Contribution

It introduces a novel acousto-electric method to directly observe bulk domain formation in microwave-induced zero-resistance states, advancing understanding of non-equilibrium electronic phases.

Findings

SAW velocity signatures confirm bulk origin of phenomena

SAW response depends on domain orientation

Demonstrates inhomogeneous phase formation in 2D electron systems

Abstract

Surface Acoustic Waves (SAW) have been utilized to investigate the properties of a two-dimensional electron system, subjected to a perpendicular magnetic field and monochromatic microwave radiation, in the regime where the so-called microwave-induced zero-resistance states form. Contrary to conventional magneto-transport in Hall bar and van der Pauw geometries, the collimated SAW beam probes only the bulk of the electronic system exposed to this wave. Clear signatures appear in the SAW propagation velocity corroborating that neither contacts, nor sample edges are a root source for their emergence. By virtue of the directional nature of this probing method and with the assistance of theoretical modelling, we were also able to demonstrate that the SAW response depends on the angle between its propagation vector and the orientation of domains which spontaneously form when zero-resistance is observed in transport. This confirms in unprecedented manner the formation of an inhomogeneous phase under these non-equilibrium conditions.