In-plane magnetic field dependence of cyclotron relaxation time in a Si two-dimensional electron system

Cyclotron resonance of two-dimensional electrons is studied for a high-mobility Si/SiGe quantum well in the presence of an in-plane magnetic field, which induces spin polarization. The relaxation time $\tau_{CR}$ shows a negative in-plane magnetic field dependence, which is similar to that of the transport scattering time $\tau_t$ obtained from dc resistivity. The resonance magnetic field shows an unexpected negative shift with increasing in-plane magnetic field.