On dynamical ordering in a 2D electron crystal confined in a narrow channel geometry

TL;DR

This study investigates the nonlinear transport behavior of a 2D electron crystal on superfluid helium confined in a narrow channel, revealing that oscillations and negative differential conductivity arise from dynamical decoupling and recoupling processes.

Contribution

The paper provides time-resolved measurements showing that oscillating transport characteristics are due to dynamical slipping and sticking of the electron crystal, challenging previous explanations of a nonequilibrium phase transition.

Findings

Oscillations linked to dynamical decoupling and recoupling of the electron crystal.

Negative differential conductivity observed in transport measurements.

Effect is intrinsic and related to interaction with surface excitations.

Abstract

We present both time-averaged and time-resolved transport measurements of a two-dimensional electron (Wigner) crystal on the surface of superfluid helium confined in a narrow microchannel. We find that the field-current characteristics of the driven crystal obtained by the time-averaged measurements exhibit oscillations and negative differential conductivity. This unusual transport behavior was observed previously by Glasson et al. [Phys. Rev. Lett. 87, 176802 (2001)] and was attributed to a nonequilibrium transition of the electron system to a novel dynamically ordered phase of current filaments aligned along the channels. Contrarily to this explanation, our time-resolved transport measurements reveal that oscillating field-current characteristics appear due to dynamical decoupling (slipping) and recoupling (sticking) of the uniform electron crystal to the liquid helium substrate. Our result demonstrates that this unusual non-linear transport effect is intrinsic, does not depend on the device geometry, and is associated with the dynamical interaction of Wigner crystal with the surface excitations of the liquid substrate.