A nuclear relaxation study of hopping in p-type InSb

Abstract

The authors present a low-temperature study of the charge and spin dynamics of holes, at density approximately 1016 cm-3, in the narrow-band semiconductor InSb. The conductivity and Hall coefficient are used to characterize the charge dynamics, and nuclear spin-lattice relaxation is used to monitor the electron spin dynamics. They have two samples; the first is cadmium-doped, p-type, uncompensated, of density 1.5*1016 cm-3 and the other is an initially identical sample, but additionally compensated by neutron transmutation doping to reduce the hole density to 7.2*1015 cm-3. This dramatically increases the mobility in the hopping regime, by reducing correlation effects. An unusual nuclear relaxation rate enhancement at low field and at low temperatures is monitored for all three nuclei, 115In, 121,123Sb, over a wide field range; high field quenches the effect. The authors discuss possible nuclear relaxation mechanisms and speculate that the effect is due to electron spin fluctuations associated with the amorphous antiferromagnetic nature of the sample in which the effect is observed, which has a dopant density close to the critical density for the metal-non-metal transition.