POSSIBLE WIGNER SOLID-PHASE TRANSITIONS IN A SERIES OF HIGH-CARRIER-DENSITY 2-DIMENSIONAL HOLE GASES

Transport measurements on a series of high-mobility, high-carrier-dens ity (1.0 x 10(11) less-than-or-equal-to n(s), less-than-or-equal-to 1. 6 x 10(11) cm-2) 2D hole Systems in fields up to 30 T and temperatures down to 30 mK show transitions into a very-high-resistance state at a range of Landau level filling factors (v) near 2/7. The insulating st ate shows clear voltage threshold behaviour and strong temperature dep endence consistent with a strongly pinned Wigner solid. We also presen t measurements on a gated 2D hole gas which enabled the systematic var iation of the carrier density near the Wigner solid phase boundary.