DIRECT OBSERVATION OF MANY-ELECTRON MAGNETOCONDUCTIVITY IN A NONDEGENERATE 2D ELECTRON LIQUID

The magnetoconductivity sigma(B) of two-dimensional electrons on liqui d helium was measured above 1 K, using high-precision Corbino electrod es. In low magnetic fields B, sigma(0)/sigma(B) = 1 + (muB)2 as in the Drude model, where mu is the zero-field mobility due to scattering by He-4 vapor atoms, even for muB >> 1. At higher fields sigma(0)/sigma( B) becomes density dependent due to many-electron effects, in excellen t agreement with the theory of Dykman. Only at the highest fields, or the lowest densities, does sigma(B) approach the theoretical single-pa rticle magnetoconductivity.