Sliding Wigner solid on liquid ⁴He

We report a systematic experimental study of the anomalous nonlinear magnetotransport in the Wigner solid (WS) trapped on a liquid ⁴He surface. The ac Corbino conductivity σ_xx exhibits an abrupt jump at a certain driving voltage. The threshold input voltage V_th for the σ_xx jump varies as V_th ∝ B^-0.8ω^-1n_s^1.5E _⊥, where B, ω, n_s, and E_⊥ are magnetic field, frequency, electron density and pressing electric field, respectively. We interpret the σ_xx jump as the transition between the WS accompanied with the periodic ⁴He surface deformation and the WS which decouples from the surface, due to the large driving force. A simple model is presented: The rigid-potential sliding model qualitatively explains the above mentioned behaviors of V_th. We have found that the dependences of σ_xx on B and E_⊥ are different from those of the liquid phase. The anomalous behaviors of σ_xx play a crucial role on the sliding model.