Magneto-optical evidence of the percolation nature of the metal-insulator transition in the 2D electron system

TL;DR

This study provides magneto-optical evidence that the metal-insulator transition in disordered 2D electron systems involves a percolation process, with a phase separation into liquid and localized states near the transition point.

Contribution

It demonstrates, through combined transport and magneto-luminescence measurements, that the MIT in 2D electron systems is associated with a percolation transition involving phase separation.

Findings

Identification of two components in optical signals: exponential decay and power-law tail.

The MIT occurs near the filling factor where the liquid phase occupies half the sample area.

Evidence of phase separation into liquid and localized electron phases near the transition.

Abstract

We compare the results of the transport and time-resolved magneto-luminescence measurements in disordered 2D electron systems in GaAs-AlGaAs heterostructures in the extreme quantum limit, in particular, in the vicinity of the metal-insulator transition (MIT). At filling factors $\nu <1$, the optical signal has two components: the single-rate exponentially decaying part attributed to a uniform liquid and a power-law long-living tail specific to a microscopically inhomogeneous state of electrons. We interprete this result as a separation of the 2D electron system into a liquid and localized phases, especially because the MIT occurs strikingly close to those filling factors where the liquid occupies ${1\over 2}$ of the sample area (the percollation threshold condition in two-component media).