Mass-induced Coulomb drag in capacitively coupled superconducting nanowires

TL;DR

This paper explores how Coulomb drag manifests in capacitively coupled superconducting nanowires, revealing a mass-induced mechanism that enables finite drag voltage near quantum critical points.

Contribution

It introduces a novel mass-induced Coulomb drag mechanism in superconducting nanowires, highlighting the role of a mass gap in enabling finite drag voltage.

Findings

Finite drag voltage appears when the second wire develops a mass gap.

Drag coefficient varies from weak in short wires to maximal in long wires.

A semiclassical model explains the synchronization of plasmon modes.

Abstract

We investigate Coulomb drag in a system of two capacitively coupled superconducting nanowires. In this context, drag refers to the appearance of a stationary voltage in the passive wire in response to a current bias applied to the active one. Quantum phase slips (QPS) in the biased wire generate voltage fluctuations that can be transmitted to the other. Using perturbative and semiclassical approaches, we show that when both wires are superconducting the induced voltage vanishes due to exact cancellation of plasmon contributions. By contrast, when the second wire is tuned below the superconductor-insulator transition and develops a mass gap, this cancellation is lifted and a finite drag voltage emerges. The drag coefficient exhibits a crossover from weak drag in short wires to a maximal value set by the mutual capacitance in long wires. A semiclassical picture of voltage pulse propagation clarifies the physical origin of the effect: the mass term synchronizes plasmon modes and prevents complete cancellation of induced signals. Our results establish a mechanism of mass-induced Coulomb drag in low-dimensional superconductors and suggest new routes for probing nonlocal transport near quantum criticality.