High-frequency nonlinear conductivity of a two-dimensional Wigner Crystal

The Wigner solid state of electrons floating above the surface of superfluid helium exhibits a characteristic non-linear transport response known as the Bragg-Cherenkov effect [1]. This phenomenon arises from the collective interaction between the electron crystal and the bosonic field of capillary waves (ripplons) on the helium surface. Here we present high-frequency transport measurements of microchannel confined electrons on helium to probe the interaction between the electron system and the thermal ripplonic bath. The measurements are carried out over a wide range of frequency from 0.1-170 MHz via capacitively coupled lock-in techniques. From these measurements, we identify the persistence of Bragg-Cherenkov scattering throughout this high-frequency domain. We compare the results to a theoretical model describing the effect of the high-frequency drive on the crystalline order of the electron solid.

[1] M. I. Dykman and Yuri G. Rubo, Phys. Rev. Lett. 78, 4813 (1997)