Spin relaxation in InSb and InAs by 1- and 2-colour spectroscopy with free electron and solid state lasers

We report time-resolved measurement of spin lifetimes in both bulk and quantum well narrow gap semiconductors (NGSs) at 300K. We have used both free electron and solid state laser sources from 3 to 7 μm and quarter wave plates to produce circularly polarised pump and probe beams. We previously demonstrated that spin flip (Elliott-Yafet, EY) scattering dominates in Hg_0.78Cd_0.22Te due to strong lattice scattering. In contrast, spin unphasing (D´Yakonov-Perel, DP) scattering controls the loss of polarisation in intrinsic InSb and InAs due to the higher mobility, giving spin lifetimes, τ_s, of ∼20 ps at 300 K. We report first measurements of τ_s of ∼17 ps in InSb/InAlSb quantum wells.