Spin-orbit scattering time and dephasing time of carriers in two-dimensional HgTe-CdTe superlattices and heterojunctions

Weak-localization studies of the two-dimensional electron gas in heterostructures made of HgTe and CdTe are reported. Because of the small effective mass, the diffusion constant D is unusually large (824 cm2/s). By fitting the weak-field transverse magnetoresistance data from high-mobility samples (50?0 cm2/V? R=720 /) to the calculation of Hikami, Larkin, and Nagaoka, we have determined the temperature (T) dependence of the spin-orbit scattering time and the dephasing time of the carriers. The system is shown to have dominant spin-orbit scattering. (The spin-orbit rate is 0.6 times the elastic scattering rate.) The dephasing time which is linear in T agrees in magnitude with a calculation by Altshuler, Aronov, and Khmelnitskii. Evidence for significant Coulomb interaction effects is obtained from the zero-field conductivity. However, the magnitude of the interaction parameter F derived from the plot of the resistance versus lnT strongly disagrees with existing theories. Prominent anomalous magnetoresistance is also seen in the longitudinal geometry. The data are compared with the interaction theory (Zeeman splitting) and the weak-localization theory. Results from high-resistance (30 k/) samples which indicate the breakdown of perturbation theory are also reported.