Suppression of spin decay in a laterally confined two-dimensional electron gas

P. Altmann¹, M. P. Walser¹, C. Reichl², W. Wegscheider² and G. Salis¹

IBM Research, Zurich, Switzerland¹
ETH Zurich, Switzerland²

The spin lifetime of a two-dimensional electron gas in a semiconductor quantum well is typically limited by the spin-orbit interaction. A lateral confinement of the electron gas to a width smaller than the spin-orbit length is predicted to reduce the spin decay rate quadratically with the confinement width. We experimentally investigate this effect by studying the dynamics of electron spins in etched GaAs wire structures of 1–80 μm width. Using the magneto-optical Kerr effect with high spatial resolution, we spatially map the diffusive expansion of locally excited spin polarization. We observe a strong suppression of spin decay at the transition to one-dimensional diffusion which is explained by the reduced dilution of the injected spin polarization. In addition to this contribution, the intrinsic spin lifetime significantly increases with decreasing wire width. Only a small increase is observed if Rashba and Dresselhaus spin-orbit interactions are balanced. We find that for small wire widths, the spin lifetime saturates at the value for a two-dimensional electron gas with perfectly balanced spin-orbit interaction, suggesting that these rates are both limited by the cubic Dresselhaus interaction.