HALL-VELOCITY LIMITED MAGNETOCONDUCTIVITY IN A CLASSICAL 2-DIMENSIONAL WIGNER CRYSTAL

The magnetoconductivity sigma(xx)(B) of a classical two-dimensional el ectron crystal on superfluid He-4 is nonlinear. Experimentally, we fin d a contribution to sigma(xx)(B) which, at constant field B, gives sig ma(xx)(B) proportional to J(x), the current density, while at constant current, sigma(xx)(B) proportional to 1/B. For increasing-J(x), the H all velocity upsilon(H) slowly approaches the ripplon velocity upsilon (1) at the first reciprocal lattice vector, due to strong electron-rip plon interactions with the helium. The magnetoconductivity then decrea ses sharply for upsilon(H) > upsilon(1).