High-field cyclotron resonance in the conduction bands of GaSb and effective-mass parameters at the<i>L</i>points

Abstract

We have observed infrared cyclotron resonance in the conduction band at both the \ensuremath{\Gamma} and the L points in n-type GaSb at high magnetic fields up to 500 T. We observed cyclotron resonance signals from the \ensuremath{\Gamma} and the L points separately for temperatures higher than 100 K. The resonance at the L point was observed in fields higher than 60 T. From the photon-energy dependence of the effective mass for magnetic fields parallel to the 〈100〉 and the 〈111〉 directions, we obtained the longitudinal and the transverse effective masses, ${m}_{l}$ and ${m}_{t},$ as $(1.4\ifmmode\pm\else\textpm\fi{}{0.2)m}_{0}$ and $(0.085\ifmmode\pm\else\textpm\fi{}{0.006)m}_{0}$ at the band edge of the L point. The magnetic-field-induced $\ensuremath{\Gamma}\ensuremath{-}L$ crossover was estimated to take place at approximately 125 T for magnetic fields parallel to the 〈100〉 direction from the field dependence of the absorption intensity at the \ensuremath{\Gamma} and the L points and a calculation of the $N=0$ Landau levels at the \ensuremath{\Gamma} and the L points. The nonparabolicity at the L point is found to be larger than that at the \ensuremath{\Gamma} point. For the \ensuremath{\Gamma} point, we obtained a band-edge mass of ${0.039m}_{0}$ from the photon-energy dependence of the effective mass.