Enhancement of Spin Lifetime in Gate-Fitted InGaAs Narrow Wires

We investigated the spin lifetime in gate-fitted InGaAs narrow wires from magnetotransport measurement. Applying positive gate bias voltage, the spin lifetimes in narrow wires became more than one order longer than those obtained from a Hall bar sample with two-dimensional electron gas. This enhancement of spin lifetime in gated wires is the first experimental evidence of dimensional confinement and resonant spin-orbit interaction effect controlled by gate bias voltage. Spin relaxation due to the cubic Dresselhaus term is negligible in the present InGaAs wires.