Far-infrared magneto-optics of thin film p-PbTe

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Abstract
Magneto-optical studies between 8K and 30K in high-mobility thin films of p-PbTe with carrier concentrations from 1.5*1023 m-3 to 6.8*1023 m-3 are reported. The major observations are (a) cyclotron resonances whose frequencies are almost linear with magnetic field up to 80 cm-1 giving values of mT/m0 between 0.027 and 0.032 and mL/m0 between 0.30 and 0.34; and (b) a pinning of the observed structure in the transmission above 8 T. When this pinned structure is fitted by varying epsilon c, it is found that omega c saturates at some value considerably in excess of the LO phonon frequency ( omega LO) (the pinning frequency in low carrier concentration semiconductors) but close to the coupled plasmon-phonon frequency ( omega LO2+ omega p2)12/. A strong temperature dependence (an 8% shift from 8K to 30K) is observed in the transverse mass cyclotron resonance which can be partly explained in terms of thermal excitation into a nonparabolic band, even with the simplifying assumption of an energy independent collision time.