Anomalous magneto-transport and optical transmission of PbTe thin films

Anomalous temperature dependence has been observed in the magneto-transport of PbTe thin films on BaF₂. A factor-of-10 increase in the longitudinal magnetoresistance rho _zz(B) at high fields is seen for decreasing temperature in the range 12<T<0.3 K, while the Hall coefficient changes by less than 20%. These observations suggest that the localisation of carriers on impurities or magnetic freeze-out is not occurring, contrary to the case of HgCdTe. Far-infrared transmission using lambda _L=70.6 and 118.8 mu m in magnetic fields up to 13 T exhibits temperature dependence in cyclotron resonance, dielectric anomaly and spin resonance transitions. The temperature dependence in n-type PbTe is due primarily to the transfer of carriers from the lowest-energy strain-split (111) valley to the higher-energy (111) valleys as the temperature is increased. The transfer of carriers is not the origin of the anomalous magneto-transport, however, since below T approximately=2 K no transfer of carriers occurs, while the transport temperature dependence continues for another order of magnitude in temperature.