Nanomechanical detection of vortices in an electron fluid

TL;DR

This paper demonstrates a novel nanomechanical method to directly detect and analyze electron vortices in a viscous electron fluid, revealing their behavior through mechanical vibrations.

Contribution

It introduces a simple nanomechanical approach using a suspended resonator with a circular cavity to visualize electron vortices directly.

Findings

Detected ballistic and hydrodynamic vortices

Traced temperature-driven vortex crossover

Showed viscosity influences nanoelectromechanical response

Abstract

Electron vortices are the quintessential signature of a viscous electron fluid. For decades, their detection relied on indirect transport measurements with persistently debated interpretations. Recently, scanning magnetometry enabled direct visualization, yet these techniques demand considerable sophistication. Here we introduce a conceptually different and inherently simpler paradigm based on nanomechanics. By integrating a circular cavity into a suspended resonator, we create a vortex whose circulating current generates a magnetic moment. In an in-plane magnetic field, this moment experiences a torque, driving vibrations that directly reveal the vortex's presence and nature. We detect ballistic and hydrodynamic vortices and trace their temperature-driven crossover. Our work establishes nanomechanics as a platform for electron hydrodynamics, showing that viscosity - subtle in transport - is one of the dominant factors shaping nanoelectromechanical response.