Eugene Ya. Sherman

Probing variations of the Rashba spin-orbit coupling at the nanometre scale

Scanning tunnelling spectroscopy provides access to the spatial variations in the strength of Rashba spin–orbit coupling in a two-dimensional electron system, with local fluctuations shown to cause spin dephasing. As the Rashba effect is an electrically tunable spin–orbit interaction1, it could form the basis for a multitude of applications2,3,4, such as spin filters3, spin transistors5,6 and quantum computing using Majorana states in nanowires7,8. Moreover, this interaction can determine the spin dephasing9 and antilocalization phenomena in two dimensions10. However, the real space pattern of the Rashba parameter, which critically influences spin transistors using the spin-helix state6,11,12 and the otherwise forbidden electron backscattering in topologically protected channels13,14, is difficult to probe. Here, we map this pattern down to nanometre length scales by measuring the spin splitting of the lowest Landau level using scanning tunnelling spectroscopy. We reveal strong fluctuations correlated with the local electrostatic potential for an InSb inversion layer with a large Rashba coefficient (∼1 eV A). This type of Rashba field mapping enables a more comprehensive understanding of its fluctuations, which might be decisive towards robust semiconductor-based spintronic devices.

Anisotropic spin dephasing in a (110)-grown high-mobility GaAs/AlGaAs quantum well measured by resonant spin amplification technique

Spin dynamics in zincblende two-dimensional electron systems is usually dominated by the Dyakonov-Perel spin dephasing mechanism resulting from the underlying spin-orbit fields. An exceptional situation is realized in symmetrically grown and doped GaAs/AlGaAs quantum wells grown along the [110] direction, where the Rashba contribution is negligible and the effective Dresselhaus spin-orbit field is perpendicular to the sample plane. In such a system the spin dephasing times for in- and out-of-plane crystallographic directions are expected to be strongly different and the out-of-plane spin dephasing time is significantly enhanced as compared with conventional systems. We observe the spin relaxation anisotropy by resonant spin amplification measurements in a 30 nm wide double-sided symmetrically δ-doped single quantum well with a very high mobility of about 3•106 cm2/Vs at 1.5K. A comparison of the measured resonant spin amplification traces with the developed theory taking into account the spin dephasing anisotropy yields the dephasing times whose anisotropy and magnitudes are in-line with the theoretical expectations.

Pumped double quantum dot with spin-orbit coupling

We study driven by an external electric field quantum orbital and spin dynamics of electron in a one-dimensional double quantum dot with spin-orbit coupling. Two types of external perturbation are considered: a periodic field at the Zeeman frequency and a single half-period pulse. Spin-orbit coupling leads to a nontrivial evolution in the spin and orbital channels and to a strongly spin- dependent probability density distribution. Both the interdot tunneling and the driven motion contribute into the spin evolution. These results can be important for the design of the spin manipulation schemes in semiconductor nanostructures.PACS numbers: 73.63.Kv,72.25.Dc,72.25.Pn