The thermopower of a high-mobility Si-MOSFET around the metal-insulator transition

The thermopower of a high-mobility Si-MOSFET sample has been measured as a function of electron density around the metal–insulator transition over the temperature range of about 0.5–4 K. Both diffusion and phonon drag effects are clearly seen, the latter for the first time in an insulator. Each contribution appears to vary smoothly through the MIT without reflecting the strong variation observed in the conductivity.