Vortex density waves and negative absolute resistance in patterned superconductors

TL;DR

This paper theoretically investigates vortex dynamics in patterned superconductors, revealing vortex-density waves, phase separation, and negative resistance states due to nonlinear vortex interactions and external drives.

Contribution

It introduces the existence of vortex-density waves and negative absolute resistance in superconductors with obstacle arrays, supported by simulations and analytical models.

Findings

Vortex-density waves form via phase separation at certain currents.

Waves move at nearly constant speed, causing voltage plateaus.

Negative absolute mobility leads to negative resistance states.

Abstract

We study theoretically dynamical phases of vortices in superconducting films with arrays of obstacles. By performing a series of molecular dynamics simulations and analytical calculations, we demonstrate the existence of a phase of soliton-like vortex-density waves appearing in a wide range of parameters. These waves are formed by a self-assembled phase separation process induced by strongly nonlinear density fluctuations of the moving vortex matter above a certain critical driving current. At high vortex concentrations, the waves move at an approximately current-independent speed resulting in a wide plateau in the voltage-current characteristics. At stronger drives, the vortex system enters into a fully jammed (zero-voltage) phase. By combining ac and dc drives, the interplay between the vortex-density-wave and jammed phases leads to the observation of negative absolute mobility of vortices, which induces the superconducting film into a negative resistance state.