Spin relaxation of conduction electrons inn-type indium antimonide at low temperature

We present a theory of the spin relaxation time of the conduction electrons in indium antimonide at liquid-helium temperature; earlier work on the subject is reviewed and discussed. The theory is compared with our measurements and the experimental data available in the literature: The relevant mechanism in highly doped samples ($n\gtrsim 5\times {10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$) is shown to be scattering by ionized impurities. The spin-flip matrix element arises from the admixture of different spin states in the Bloch functions of the conduction band (Elliott process). Good agreement with experiment is obtained with no adjustable parameter. In the less-doped samples ($n\lesssim 5\times {10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$) the currently invoked relaxation mechanism (modulation of the $g$ factor or of the hyperfine interactions by the motion of the electrons) is shown to be ineffective. The impurity Elliott process is reconsidered; the effect of disorder is included by using a model of quasimacroscopic fluctuations of the electron density, which qualitatively accounts for the observed linewidths.