Anomalous thermopower of a quasi-two-dimensional low-density metallic hole gas

We study the thermopower S and the resistance R of a low-density quasi-two-dimensional hole gas in the metallic regime at low temperatures (T's). Long-range interface-roughness fluctuations are found to explain the sign anomaly and the sign reversal of the recently observed T-dependent S. Two mechanisms showing similar S(R) can yield very different R(S), indicating that S and R play a complementary role toward understanding the transport mechanism.