Spin dynamics in p-doped semiconductor nanostructures subject to a magnetic field tilted from the Voigt geometry

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/Al_{0.3}Ga_{0.7}As single QW and showing that our model can reproduce experimentally observed signals.Comment: 9 pages, 3 figures; corrected typo

Decoherence-assisted initialization of a resident hole spin polarization in a two-dimensional hole gas

We investigate spin dynamics of resident holes in a p-modulation-doped GaAs/Al$_{0.3}$Ga$_{0.7}$As 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 in-plane 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.Comment: 10 pages, 6 figures; moderate modifications, one new figur

Epitaxial Growth of Room-Temperature Ferromagnetic MnAs Segments on GaAs Nanowires via Sequential Crystallization

We investigate the incorporation of manganese into self-catalyzed GaAs nanowires grown in molecular beam epitaxy. Our study reveals that Mn accumulates in the liquid Ga droplet and that no significant incorporation into the nanowire is observed. Using a sequential crystallization of the droplet, we then demonstrate a deterministic and epitaxial growth of MnAs segments at the nanowire tip. This technique may allow the seamless integration of multiple room temperature ferromagnetic segments into GaAs nanowires with high-crystalline quality

Spin dynamics in two-dimensional electron and hole systems revealed by resonant spin amplification

Understanding and controlling the spin dynamics in semiconductor heterostructures is a key requirement for the design of future spintronics devices. In GaAs-based heterostructures, electrons and holes have very different spin dynamics. Some control over the spin-orbit fields, which drive the electron spin dynamics, is possible by choosing the crystallographic growth axis. Here, (110)-grown structures are interesting, as the Dresselhaus spinorbit fields are oriented along the growth axis and therefore, the typically dominant Dyakonov-Perel mechanism is suppressed for spins oriented along this axis, leading to long spin depasing times. By contrast, hole spin dephasing is typically very rapid due to the strong spin-orbit interaction of the p-like valence band states. For localized holes, however, most spin dephasing mechanisms are suppressed, and long spin dephasing times may be observed. Here, we present a study of electron and hole spin dynamics in GaAs-AlGaAs-based quantum wells. We apply the resonant spin amplification (RSA) technique, which allows us to extract all relevant spin dynamics parameters, such as g factors and dephasing times with high accuracy. A comparison of the measured RSA traces with the developed theory reveals the anisotropy of the spin dephasing in the (110)-grown two-dimensional electron systems, as well as the complex interplay between electron and hole spin and carrier dynamics in the two-dimensional hole systems