Hall-velocity limited magnetoconductivity in a classical two-dimensional Wigner crystal

The magnetoconductivity sxx(B) of a classical two-dimensional electron crystal on superfluid 4He is nonlinear. Experimentally, we find a contribution to sxx(B) which, at constant field B, gives sxx(B)¿Jx, the current density, while at constant current, sxx(B)¿1/B. For increasing Jx, the Hall velocity ¿H slowly approaches the ripplon velocity ¿l at the first reciprocal lattice vector, due to strong electron-ripplon interactions with the helium. The magnetoconductivity then decreases sharply for ¿H>¿1.