Magnetic Field Effects and Transverse Ratchets in Charge Lattices Coupled to Asymmetric Substrates

TL;DR

This paper investigates how magnetic fields influence charge lattices on asymmetric substrates, revealing novel transverse ratchet effects, Hall angle reversals, and efficiency variations due to gyrotropic forces.

Contribution

It introduces the concept of magnetic field-induced transverse ratchet motion and analyzes the resulting complex behaviors in charge lattices on asymmetric substrates.

Findings

Transverse ratchet motion occurs when ac drive is perpendicular to substrate asymmetry.

Magnetic fields cause reversals in ratchet effect and Hall angle.

Ratchet efficiency shows nonmonotonic behavior at high magnetic fields.

Abstract

We examine a charge lattice coupled to a one-dimensional asymmetric potential in the presence of an applied magnetic field, which induces gyrotropic effects in the charge motion. This system could be realized for Wigner crystals in nanostructured samples, dusty plasmas, or other classical charge-ordered states where gyrotropic motion and damping can arise. For zero magnetic field, an applied external ac drive can produce a ratchet effect in which the particles move along the easy flow direction of the substrate asymmetry. The zero field ratchet effect can only occur when the ac drive is aligned with the substrate asymmetry direction; however, when a magnetic field is added, the gyrotropic forces generate a Hall effect that leads to a variety of new behaviors, including a transverse ratchet motion that occurs when the ac drive is perpendicular to the substrate asymmetry direction. We show that this system exhibits commensuration effects as well as reversals in the ratchet effect and the Hall angle of the motion. The magnetic field also produces a nonmonotonic ratchet efficiency when the particles become localized at high fields.