Noise Thermal Impedance of a Diffusive Wire

TL;DR

This paper introduces the concept of noise thermal impedance in diffusive wires, providing a new method to measure electron-phonon, diffusion, and electron-electron interaction times through frequency-dependent noise analysis.

Contribution

It presents the noise thermal impedance as a novel tool to access microscopic interaction times in diffusive conductors, extending beyond traditional noise measurements.

Findings

Noise thermal impedance relates to electron-phonon interaction time.

It allows measurement of diffusion time in short wires.

Real part of impedance provides electron-electron inelastic time.

Abstract

The current noise density S of a conductor in equilibrium, the Johnson noise, is determined by its temperature T: S=4kTG with G the conductance. The sample's noise temperature Tn=S/(4kG) generalizes T for a system out of equilibrium. We introduce the "noise thermal impedance" of a sample as the amplitude of the oscillation of Tn when heated by an oscillating power. For a macroscopic sample, it is the usual thermal impedance. We show for a diffusive wire how this (complex) frequency-dependent quantity gives access to the electron-phonon interaction time in a long wire and to the diffusion time in a shorter one, and how its real part may also give access to the electron-electron inelastic time. These times are not simply accessible from the frequency dependence of S itself.