Critical role of mobility in determination of spin relaxation in narrow gap semiconductor quantum wells.

Electron spin polarisation decay in n-type semiconductor quantum wells is via Elliot-Yafet spin-flip scattering or D’yakonov-Pere’ spin dephasing. The strength of the dephasing may be controlled by the quantum well design, and is much more sensitive in narrow bandgap antimonides than in arsenides. We show that the mobility, not the temperature, is critical in determining which mechanism dominates and that above 1 m²V⁻¹s⁻¹ in 20nm wide InSb quantum wells it is dephasing. We also show that the spin lifetime (¤cl/T) is longest at the critical mobility.