SLIDING WIGNER SOLID ON LIQUID-HE-4

We report a systematic experimental study of the anomalous nonlinear m agnetotransport in the Wigner solid (WS) trapped on a liquid He-4 surf ace. The ac Corbino conductivity sigma(xx) exhibits an abrupt jump at a certain driving voltage. The threshold input voltage V-th for the si gma(xx) jump varies as V(th)proportional to B(-0.8)omega(-1)n(s)(1.5)E (perpendicular to), where B, omega, n(s), and E(perpendicular to) are magnetic field, frequency, electron density and pressing electric fiel d, respectively. We interpret the sigma(xx) jump as the transition bet ween the WS accompanied with the periodic He-4 surface deformation and the WS which decouples from the surface, due to the large driving for ce. A simple model is presented: The rigid-potential sliding model qua litatively explains the above mentioned behaviours of V-th. We have fo und the dependencies of sigma(xx) on B and E(perpendicular to) are dif ferent from those of the liquid phase. The anomalous behaviours of sig ma(xx) play a crucial role on the sliding model.