No abstract

The spin–orbit coupling (SOC) in semiconductors is strongly influenced by structural asymmetries, as prominently observed in bulk crystal structures that lack inversion symmetry. Here we study an additional effect on the SOC: the asymmetry induced by the large interface area between a nanowire core and its surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell nanowires demonstrate optical spin injection into a single free-standing nanowire and determine the effective electron g-factor of the hexagonal GaAs wurtzite phase. The spin relaxation is highly anisotropic in time-resolved micro-photoluminescence measurements on single nanowires, showing a significant increase of spin relaxation in external magnetic fields. This behaviour is counterintuitive compared with bulk wurtzite crystals. We present a model for the observed electron spin dynamics highlighting the dominant role of the interface-induced SOC in these core/shell nanowires. This enhanced SOC may represent an interesting tuning parameter for the implementation of spin–orbitronic concepts in semiconductor-based structures.

We investigate spin dynamics of resident holes in a p-modulation-doped GaAs/Al0.3Ga0.7As single quantum well. Time-resolved Faraday and Kerr rotation, as well as resonant spin amplification, are utilized in our study. We observe that nonresonant or high power optical pumping leads to a resident hole spin polarization with opposite sign with respect to the optically oriented carriers, while low power resonant optical pumping only leads to a resident hole spin polarization if a sufficient inplane magnetic field is applied. The competition between two different processes of spin orientation strongly modifies the shape of resonant spin amplification traces. Calculations of the spin dynamics in the electron-hole system are in good agreement with the experimental Kerr rotation and resonant spin amplification traces and allow us to determine the hole spin polarization within the sample after optical orientation, as well as to extract quantitative information about spin dephasing processes at various stages of the evolution.

Nanowire geometry and crystalline structure under Mn supply Figure S1(a) and S1(b) show scanning electron microscopy (SEM) images of regular, Mn-free GaAs nanowires, grown as a control experiment, and nanowires grown under (Ga,Mn)Assupply ( rst sample series described in the article). On both samples the wires display the same length, indicating that the supply of Mn does not inhibit the VLS growth mechanism.The only di erence visible in SEM concerns the catalyst droplet: solidi ed Ga-droplets are perfectly spherical ( Figure S1(a)), while solidi ed (Ga,Mn)-alloy droplets are partially faceted ( Figure S1(b)). The results obtained in SEM for the second sample series described in the article (GaAs NWs with liquid Ga droplet exposed to Mn) are identical to Figure S1(b). The results obtained in SEM for the third sample series (GaAs NWs exposed to Mn 1

We develop a theoretical description of the spin dynamics of resident holes in a p-doped semiconductor quantum well (QW) subject to a magnetic field tilted from the Voigt geometry. We find the expressions for the signals measured in time-resolved Faraday rotation (TRFR) and resonant spin amplification (RSA) experiments and study their behavior for a range of system parameters. We find that an inversion of the RSA peaks can occur for long hole spin dephasing times and tilted magnetic fields. We verify the validity of our theoretical findings by performing a series of TRFR and RSA experiments on a p-modulation doped GaAs/Al0.3Ga0.7As single QW and showing that our model can reproduce experimentally observed signals.arXiv:1306.6363v2 [cond-mat.mes-hall]