Spin dynamics in spiral magnetic structures has been investigated. It has been shown that the internal spatially dependent magnetic field in such structures produces a new mechanism of spin relaxation.
Topological effects of a spiral dislocation on an electron are investigated when it is confined to a hard-wall confining potential. Besides, it is analysed the influence of the topology of the spiral dislocation on the interaction of the electron with a non-uniform radial electric field and a uniform axial magnetic field. It is shown that a discrete spectrum of energy can be obtained in all these cases. Moreover, it is shown that there is one case where an analogue of the Aharonov-Bohm effect for bound states is yielded by the topology of the spiral dislocation.
Electron-phonon and exciton-phonon interactions in nanoclusters are formulated and computed under the framework of GW-BSE (Bethe-Salpeter equation) approach. The phonon effect is modeled with the two-particle representation for the first time. The nonradiative relaxation rates of electrons and excitons are calculated. It is uncovered that both single-phonon relaxation and multiple-phonon relaxation are significant in nanocrystals, and correspond to two types of physical processes that have totally different spectral lineshapes. Furthermore, the multiple-phonon relaxation always occurs and its …
Electron Spin Relaxation in Two Polymorphic Structures of GaN
利用投影约化方法推导出的电子自旋弛豫时间公式,从微观角度解释了电子与压电形变声子相互作用系统中电子自旋的弛豫过程.计算了GAN两种多晶结构的电子自旋弛豫时间。通过与先前报道的实验结果进行比较,获得了纤锌矿结构的压电材料常数P_pe=1.5 x 10^29 eV/m。纤锌矿和锌掺杂GaN的弛豫时间随温度和磁场的变化规律相似,但锌掺杂GAN的弛豫时间随温度和磁场的升高而减小,且减小速度更快。本研究还表明,在低密度下,纤锌矿GAN的电子自旋弛豫可以用Elliot-Yafet过程来解释,但在金属区域中,锌掺杂GAN的电子自旋弛豫不能用Elliot-Yafet过程来解释。
We study and compare two analytic models of graphene quantum dots for calculating charge relaxation times due to electron-phonon interaction. Recently, charge relaxation processes in graphene quantum dots have been probed experimentally and here we provide a theoretical estimate of relaxations times. By comparing a model with pure edge confinement to a model with electrostatic confinement, we find that the latter features much larger relaxation times. Interestingly, relaxation times in electrostatically defined quantum dots are predicted to exceed the experimentally observed lower bound of ~10…
We investigate the electron and hole spin relaxation in an ensemble of self-assembled InAs/In$_{0.53}$Al$_{0.24}$Ga$_{0.23}$As/InP quantum dots with emission wavelengths around $1.5$~$μ$m by pump-probe Faraday rotation spectroscopy. Electron spin dephasing due to the randomly oriented nuclear Overhauser fields is observed. At low temperatures we find a sub-microsecond longitudinal electron spin relaxation time $T_1$ which unexpectedly strongly depends on temperature. At high temperatures the electron spin relaxation time is limited by optical phonon scattering through spin-orbit interaction de…
Non-equilibrium dynamics of strongly correlated systems constitutes a fascinating problem of condensed matter physics with many open questions. Here we investigate the relaxation dynamics of Landau-quantized electron system into spin-valley polarized ground state in a gate-tunable MoSe$_2$ monolayer subjected to a strong magnetic field. The system is driven out of equilibrium with optically injected excitons that depolarize the electron spins and the subsequent electron spin-valley relaxation is probed in time-resolved experiments. We demonstrate that the relaxation rate at millikelvin tempera…
We calculate the transport relaxation time $τ_{\rm tr}$ and spin transport relaxation time $τ_{s,{\rm tr}}$ for a two-dimensional electron gas with spatially fluctuating Rashba spin-orbit interaction. These relaxation times determine the electrical and spin conductivity of the two-dimensional system, respectively. It is shown that the transport relaxation time $τ_{\rm tr}$ is a nonmonotonic function of electron energy $\varepsilon $, whereas the spin transport relaxation time $τ_{s,{\rm tr}}$ decreases with increasing $\varepsilon $, similarly to the conventional electron relaxation time $τ$ t…
We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic chains are determined by the nearest-neighbor isotropic interaction. The dependence on the crystallographic direction as well as on the atomic coordination number is analyzed via an orbital decomposition of this isotropic interaction based on the spin-cluster expansion and the difference in the local density of states…
Temperature and Electron Density Dependence of Spin Relaxation in GaAs/AlGaAs Quantum Well
利用时间分辨克尔旋转技术研究了具有不同结构对称性的GaAs/AlGaAs量子阱的自旋动力学随温度和载流子密度的变化。与非对称GaAs量子阱相比,对称GaAs量子阱的自旋弛豫时间要长得多,表明Rashba自旋轨道耦合对自旋弛豫有很强的影响. D 'yakonov-Perel'(DP)机制是GaAs/AlGaAs量子阱自旋弛豫的主要机制。自旋弛豫时间表现出非单调依赖于温度和光激发载流子密度的行为,揭示了电子-电子库仑散射的非单调温度和密度依赖性的重要作用。我们的实验观察表明,与最近发展的自旋弛豫理论的基础上微观动力学自旋布洛赫方程的方法很好的协议。
A short overview of theoretical models for the description of the relaxation processes in metals excited by a short laser pulse is presented. The main effort is given to description of different processes which are taking place after absorption of the laser pulse. Widely used two temperature model is discussed and the conditions of applicability of this model are identified. Various approaches for solving the Boltzmann kinetic equations are discussed. It is identified that in the case of low excitation limit the relaxation is determined by the emission of phonons by photoexcited electrons. The…