Interaction effects in the transport of two-dimensional holes in GaAs
  The power-law increase of the conductivity with temperature in the nominally insulating regime, recently reported for the dilute two-dimensional holes [cond-mat/0603053], is found to systematically vary with the carrier density. Based on the results from four different GaAs heterojunction-insulated-gate field-effect-transistor samples, it is shown that the power law exponent depends on a single dimensionless parameter, the ratio between the mean carrier separation and the distance to the metallic gate that screens the Coulomb interaction. This dependence suggests that the carriers form a correlated state in which the interaction effects play a significant role in the transport properties. 
Jian Huang, D. S. Novikov, D. C. Tsui, L. N. Pfeiffer, K. W. West