Long-Range Order in Electronic Transport through Disordered Metal Films

TL;DR

This paper demonstrates that ultracold atom magnetometry can detect long-range organized current patterns in disordered gold films, revealing universal scattering effects and correlations at scales much larger than grain sizes.

Contribution

It introduces ultracold atom magnetic field microscopy as a tool to observe long-range current correlations in disordered metals at room temperature.

Findings

Long-range correlations form at +/- 45 degrees to current flow.

Pattern amplitude scales inversely with film thickness, grain size, and defect concentration.

Universal scattering properties influence current pattern formation.

Abstract

Ultracold atom magnetic field microscopy enables the probing of current flow patterns in planar structures with unprecedented sensitivity. In polycrystalline metal (gold) films we observe long-range correlations forming organized patterns oriented at +/- 45 deg relative to the mean current flow, even at room temperature and at length scales orders of magnitude larger than the diffusion length or the grain size. The preference to form patterns at these angles is a direct consequence of universal scattering properties at defects. The observed amplitude of the current direction fluctuations scales inversely to that expected from the relative thickness variations, the grain size and the defect concentration, all determined independently by standard methods. This indicates that ultracold atom magnetometry enables new insight into the interplay between disorder and transport.