Momentum noise in a quantum point contact

TL;DR

This paper demonstrates that momentum noise in a quantum point contact persists on conductance plateaus and exhibits oscillatory or stepwise dependence on constriction geometry, revealing quantized features in mechanical fluctuations.

Contribution

It provides the first analysis showing momentum noise does not vanish on conductance plateaus and characterizes its geometric dependence.

Findings

Momentum noise remains finite on conductance plateaus.

Momentum noise exhibits oscillatory or stepwise dependence on constriction width.

Momentum noise shows approximate quantization related to conductance quantization.

Abstract

Ballistic electrons flowing through a constriction can transfer momentum to the lattice and excite a vibration of a free-standing conductor. We show (both numerically and analytically) that the electromechanical noise power P does not vanish on the plateaus of quantized conductance -- in contrast to the current noise. The dependence of $P$ on the constriction width can be oscillatory or stepwise, depending on the geometry. The stepwise increase amounts to an approximate quantization of momentum noise.