We have made direct pump-probe measurements of spin lifetimes in long-wavelength narrow-gap semiconductors at wavelengths between 4 and 10 µm and from 4 to 300 K. In particular, we measure remarkably long spin lifetimes ts~300 ps even at 300 K for epilayers of degenerate n-type InSb. In this material the mobility is approximately constant between 77 and 300 K, and we find that ts is approximately constant in this temperature range. In order to determine the dominant spin relaxation mechanism we have investigated the temperature dependence of ts in nondegenerate lightly n-type Hg0.78Cd0.22Te of approximately the same band-gap as InSb and find that ts varies from 356 ps at 150 K to 24 ps at 300 K. In this material lattice scattering dominates giving a T-3/2 dependence for the mobility, and we expect a strong temperature dependence of ts. There are two main models that have been invoked for describing spin relaxation in narrow-gap semiconductors: the Elliott-Yafet (EY) model which gives a T-7/2 dependence of ts in this limit and the D'yakonov-Perel model which gives a T-3/2 dependence. Our results, both in magnitude and temperature dependence of ts, imply that the EY model dominates in these materials.
|Number of pages||5|
|Journal||Physical Review B: Condensed Matter and Materials Physics|
|Publication status||Published - Jun 2003|