Non-activated transport of strongly interacting two-dimensional holes in   GaAs
  We report on the transport measurements of two-dimensional holes in GaAs field effect transistors with record low densities down to 7*10^8 cm^{-2}. Remarkably, such a dilute system (with Fermi wavelength approaching 1 micrometer) exhibits a non-activated conductivity that grows with temperature following a power law. We contrast it with the activated transport obtained from measuring more disordered samples, and discuss possible transport mechanisms in this strongly-interacting regime. 
Jian Huang, D. S. Novikov, D. C. Tsui, L. N. Pfeiffer, K. W. West