Nonmonotonic Temperature-Dependent Resistance in Low Density 2D Hole Gases

The low temperature longitudinal resistance-per-square R_xx\(T\) in ungated GaAs/Al_xGa_1-xAs quantum wells of high peak hole mobility 1.7×10⁶ cm ² V^-1 s^-1 is metallic for 2D hole density p as low as 3.8×10⁹ cm ^-2. The electronic contribution to the resistance, R_el\(T\), is a nonmonotonic function of T, exhibiting thermal activation, R_el\(T\)~exp\(-E_a/kT\), for kT<<E_F and a heretofore unnoted decay R_el\(T\)~1/T for kT>E_F. The form of R_el\(T\) is independent of density, indicating a fundamental relationship between the low- and high- T scattering mechanisms in the metallic state.