Evidence for depinning of a Wigner crystal in Hg-Cd-Te

We report measurements of the nonlinear current-voltage characteristics on low-carrier-concentration n-type samples of Hg_(0.76)Cd_(0.24)Te at high magnetic fields and low temperatures. We find the onset of nonlinear conductivity occurs at applied electric fields of less than 1 mV/cm. The effect can be easily distinguished from sample heating and is consistent with collective transport produced by the sliding of a Wigner crystal pinned by disorder. We estimate a disorder-induced correlation length of tens of micrometers