Long distance electron-electron scattering detected with point contacts

TL;DR

This study investigates electron transport in point contacts within AlGaAs/GaAs and graphene, revealing a magnetoconductance peak influenced by temperature and magnetic field, and proposing a model of transport regime transitions.

Contribution

It introduces a model describing the transition from ballistic to hydrodynamic electron flow in point contacts, supported by experimental data across various conditions.

Findings

Magnetoconductance peak width increases with temperature.

Peak amplitude varies non-monotonically with temperature.

Transport regimes transition from ballistic to hydrodynamic flow.

Abstract

We measure electron transport through point contacts in an electron gas in AlGaAs/GaAs heterostructures and graphene for a range of temperatures, magnetic fields and electron densities. We find a magnetoconductance peak around B = 0. With increasing temperature, the width of the peak increases monotonically, while its amplitude first increases and then decreases. For GaAs point contacts the peak is particularly sharp at relatively low temperatures $T\approx$1.5 K: the curve rounds on a scale of few tens of $\mu$T hinting at length scales of several millimeters for the corresponding scattering processes. We propose a model based on the transition between different transport regimes with increasing temperature: from ballistic transport to few electron-electron scatterings to hydrodynamic superballistic flow to hydrodynamic Poiseuille-like flow. The model is in qualitative and, in many cases, quantitative agreement with the experimental observations.