Conductivity of the Wigner solid on the free surface of superfluid 3He-B

We have measured the conductivity of the 2D electron crystal (the Wigner solid) trapped on the free surface of superfluid He-3-B down to 230 mu K. The resistance R(T) greatly decreases as temperature T decreases, obeying Arrhenius' law, R(T) proportional to exp(-Delta(T)/k(B)T), with Delta(T) which we assign to the superfluid energy gap. This reveals that the scattering of He-3 quasiparticles by the WS determines the transport. As the input voltage increases, an anomalous behavior dominates the resistance just below the superfluid transition. The WS provides a new experimental method for probing both the bulk and free surface of superfluid He-3.