We find that the electronic spin rotation induced by drift transport around a closed path in a wide variety of nonmagnetic semiconductors at zero magnetic field depends solely on the physical path taken. Physical paths that produce any possible spin rotation due to transport around a closed path are constructed for electrons experiencing strain or electric fields in (001), (110), or (111)-grown zincblende semiconductor quantum wells. Spin decoherence due to travel along the path is negligible compared to the background spin decoherence rate. The small size of the designed paths (<100 nm scale in GaAs) may lead to applications in nanoscale spintronic circuits.
Surface sensitive electric current measurements are important experimental tools poorly corroborated by theoretical models. We show that the drift-diffusion equations offer a framework for a consistent description of such experiments. The current flow is calculated as a perturbation of an equilibrium solution depicting the space charge layer. We investigate the accumulation and inversion layers in great detail. Relying on numerical findings, we identify the proper length parameter, the relationship of which with the length of the space charge layer is not simple. If the length parameter is lar…
Nonlinear stochastic discrete drift-diffusion theory of charge fluctuations and domain relocation times in semiconductor superlattices
提出了一种随机离散漂移扩散模型来解释弱耦合、高杂质半导体超晶格中散粒噪声的影响。它们的电流-电压特性由多个稳定的多稳态分支组成，对应于显示由畴壁分隔的两个畴的电场分布。如果初始状态对应于稳定分支中间的电压，并且突然电压被切换，使得最终电压对应于下一个分支，则畴在一定延迟时间之后重新定位。当最终电压接近第一电流分支末端的电压时，散粒噪声使延迟时间的分布从高斯分布变为第一通过时间分布。这些结果与Rogozia { \it et al}（Phys. Rev. B { \bf 64}，041308（R）（2001））的实验定性一致。
We address the increase of electron drift velocity that arises in semiconductor superlattices (SLs) subjected to constant electric and magnetic fields. It occurs if the magnetic field possesses nonzero components both along and perpendicular to the SL axis and the Bloch oscillations along the SL axis become resonant with cyclotron rotation in the transverse plane. It is a phenomenon of considerable interest, so that it is important to understand the underlying mechanism. In an earlier Letter (Phys. Rev. Lett. 114, 166802 (2015)) we showed that, contrary to a general belief that drift enhanceme…
Understanding and controlling the nanoscale transport of excitonic quasiparticles in atomically thin 2D semiconductors is crucial to produce highly efficient nano-excitonic devices. Here, we present a nano-gap device to selectively confine excitons or trions of 2D transition metal dichalcogenides at the nanoscale, facilitated by the drift-dominant exciton funnelling into the strain-induced local spot. We investigate the spatio-spectral characteristics of the funnelled excitons in a WSe2 monolayer (ML) and converted trions in a MoS2 ML using hyperspectral tip-enhanced photoluminescence (TEPL) i…
We derive generalized charge energy rate equations for organic solids and biomolecular aggregates, even when these are dynamically disordered. These equations suggest that the transport in such cases rely on both drift and diffusion phenomena. The presence of disorder and field effects makes the equations nonlinear and together with cooperativity, these enhance the charge and energy transport. The generalized drift diffusion expression connects the adiabatic band and nonadiabatic hopping transport mechanisms, well suited for any complex organic semiconductors or assemblies of bio molecular sys…
Generation of charge current by the Inverse Stern-Gerlach Effect and the suppression of spin transport due to spin counter-current exchange in semiconductors
When quantized, traces of classically chaotic single particle systems include eigenvalue statistics and scars in eigenfuntions. Since 2001, many theoretical and experimental works have argued that classically chaotic single electron dynamics influences and controls collective electron transport. For transport in semiconductor superlattices under tilted magnetic and electric fields, these theories rely on a reduction to a one-dimensional self-consistent drift model. A two-dimensional theory based on self-consistent Boltzmann transport does not support that single electron chaos influences colle…
Electrical control of spin transport is promising for achieving new device functionalities. Here we calculate the propagation of spin currents in a graphene-based spin-current demultiplexer under the effect of drift currents. We show that, using spin- and charge-transport parameters already obtained in experiments, the spin currents can be guided in a controlled way. In particular, spin-current selectivities up to 102 can be achieved for measurements over a distance of 10μm under a moderate drift current density of 20μA/μm, meaning that the spin current in the arm that is off is only 1% of the…
We find extraordinary behavior of the local two-terminal spin accumulation signals in ferromagnet (FM)/semiconductor (SC) lateral spin-valve devices. With respect to the bias voltage applied between two FM/SC Schottky tunnel contacts, the local spin-accumulation signal can show nonmonotonic variations, including a sign inversion. A part of the nonmonotonic features can be understood qualitatively by considering the rapid reduction in the spin polarization of the FM/SC interfaces with increasing bias voltage. In addition to the sign inversion of the FM/SC interface spin polarization, the influe…
State-of-the-art industrial semiconductor device modeling is based on highly efficient Drift-Diffusion (DD) models that include some quantum corrections for nanodevices. In contrast, latest academic quantum transport models are based on the non-equilibrium Green's function (NEGF) method that cover all coherent and incoherent quantum effects consistently. Carrier recombination and generation in optoelectronic nanodevices represent an immense numerical challenge when solved within NEGF. In this work, the numerically efficient Büttiker-probe model is expanded to include electron-hole recombinatio…
We report on lateral spin-caloric transport (LSCT) of electron spin packets which are optically generated by ps laser pulses in the non-magnetic semiconductor n-GaAs at $T\leq35$K. LSCT is driven by a local temperature gradient induced by an additional cw heating laser. The spatio-temporal evolution of the spin packets is probed using time-resolved Faraday rotation. We demonstrate that the local temperature-gradient induced spin diffusion is solely driven by a non-equilibrium hot spin distribution, i.e. without involvement of phonon drag effects. Additional electric field-driven spin drift exp…
Physical phenomena underlying operation of ferroelectric field-effect transistors (FeFETs) is treated within a unified simulation framework. The framework incorporates the Landau mean-field treatment of free energy of a ferroelectric and the polarization dynamics according to Landau-Khalatnikov (LK) equation. These equations are self-consistently solved with the one-dimensional metal-oxide-semiconductor (MOS) structure electrostatics and the drift-diffusion solution for the current in the semiconductor channel. Numerical simulations demonstrate, depending on the ferroelectric (FE) thickness, b…
Overcoming Configuration Bottleneck: Modular Pathways to Stable Semiconductor Spin-Qubit Arrays
National Institute of Standards and Technology（美国国家标准与技术研究院）；Joint Center for Quantum Information and Computer Science, University of Maryland（马里兰大学量子信息与计算科学联合中心）；University of Maryland（马里兰大学）；University of Pennsylvania（宾夕法尼亚大学）
