Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
We consider spin relaxation dynamics in cold Fermi gases with a pure-gauge spin-orbit coupling corresponding to recent experiments. We show that such experiments can give a direct access to the collisional spin drag rate, and establish conditions for the observation of spin drag effects. In the recent experiments the dynamics is found to be mainly ballistic leading to new regimes of reversible spin relaxation-like processes.PACS numbers: 03.75. Ss, 05.30.Fk, The development of spintronics, the branch of physics studying spin-determined dynamical and transport phenomena was mainly related to solid-state structures. In these systems, spin-orbit coupling (SOC), one of the key elements of spintronics, is well-understood [1-4] and many interesting spin-related effects have been studied experimentally and theoretically. Very recently a detailed study of spin dynamics in ultracold atomic gases has become experimentally feasible [6][7][8][9]. In particular, two systems where SOC is produced by a special design of optical fields, attracted a great deal of attention. One of them is the spin-orbit coupled Bose-Einstein condensates [5,6], with the pseudospin 1/2 degree of freedom. The other class is represented by the cold fermion isotopes 40 K in Ref. [7] and much lighter 6 Li studied in Ref. [9]. In both cases, in addition to the SOC, an effective Zeeman magnetic field can be produced optically.Typically in solids, e.g. in doped semiconductors, a disorder, randomizing motion of electrons, plays the dominant role in the spin dynamics. The electron-electron collisions become crucial only at high temperatures, or in intrinsic semiconductors with optically pumped electrons and holes [10]. From this point of view, cold atomic gases offer a unique possibility of seeing basic effects of interactions in the pure form since the disorder is absent there. The interatomic collisions lead to the spin drag determining the spin diffusion and, as we will see below, can be important for the spin dynamics in cold Fermi gases with SOC.It is well-appreciated that in the presence of strong SOC the effects of interatomic interactions in the spin dynamics are difficult to analyze as this requires tracing essentially coupled orbital and spin subsystems. Fortunately, these dynamics become uncoupled not only for vanishing SOC, but also when it corresponds to an effective non-Abelian vector potential [11-23] of a pure gauge form, which happens in a broad class of systems. Remarkably, the three-dimensional (3D) fermionic gases with SOC realized in recent experiments [7,9,24] belong to this interesting class. For a pure gauge SOC the behavior of the physical system maps to that of a system without SOC, which allows to consider effects of SOC of an arbitrary strength. In this case all qualitative features of the spin dynamics are the same as for a generic SO field, but the analysis is much easier. Here we study spin dynamics for systems with a pure gauge SO coupling, where the entire pattern even if it is complicated by the interatomic interactions, c...
We consider spin relaxation dynamics in cold Fermi gases with a pure-gauge spin-orbit coupling corresponding to recent experiments. We show that such experiments can give a direct access to the collisional spin drag rate, and establish conditions for the observation of spin drag effects. In the recent experiments the dynamics is found to be mainly ballistic leading to new regimes of reversible spin relaxation-like processes.PACS numbers: 03.75. Ss, 05.30.Fk, The development of spintronics, the branch of physics studying spin-determined dynamical and transport phenomena was mainly related to solid-state structures. In these systems, spin-orbit coupling (SOC), one of the key elements of spintronics, is well-understood [1-4] and many interesting spin-related effects have been studied experimentally and theoretically. Very recently a detailed study of spin dynamics in ultracold atomic gases has become experimentally feasible [6][7][8][9]. In particular, two systems where SOC is produced by a special design of optical fields, attracted a great deal of attention. One of them is the spin-orbit coupled Bose-Einstein condensates [5,6], with the pseudospin 1/2 degree of freedom. The other class is represented by the cold fermion isotopes 40 K in Ref. [7] and much lighter 6 Li studied in Ref. [9]. In both cases, in addition to the SOC, an effective Zeeman magnetic field can be produced optically.Typically in solids, e.g. in doped semiconductors, a disorder, randomizing motion of electrons, plays the dominant role in the spin dynamics. The electron-electron collisions become crucial only at high temperatures, or in intrinsic semiconductors with optically pumped electrons and holes [10]. From this point of view, cold atomic gases offer a unique possibility of seeing basic effects of interactions in the pure form since the disorder is absent there. The interatomic collisions lead to the spin drag determining the spin diffusion and, as we will see below, can be important for the spin dynamics in cold Fermi gases with SOC.It is well-appreciated that in the presence of strong SOC the effects of interatomic interactions in the spin dynamics are difficult to analyze as this requires tracing essentially coupled orbital and spin subsystems. Fortunately, these dynamics become uncoupled not only for vanishing SOC, but also when it corresponds to an effective non-Abelian vector potential [11-23] of a pure gauge form, which happens in a broad class of systems. Remarkably, the three-dimensional (3D) fermionic gases with SOC realized in recent experiments [7,9,24] belong to this interesting class. For a pure gauge SOC the behavior of the physical system maps to that of a system without SOC, which allows to consider effects of SOC of an arbitrary strength. In this case all qualitative features of the spin dynamics are the same as for a generic SO field, but the analysis is much easier. Here we study spin dynamics for systems with a pure gauge SO coupling, where the entire pattern even if it is complicated by the interatomic interactions, c...
We study electron spin relaxation in one-dimensional structures of finite length in the presence of Bychkov-Rashba spin-orbit coupling and boundary spin relaxation. Using a spin kinetic equation approach, we formulate boundary conditions for the case of a partial spin polarization loss at the boundaries. These boundary conditions are used to derive corresponding boundary conditions for spin drift-diffusion equation. The later is solved analytically for the case of relaxation of a homogeneous spin polarization in 1D finite length structures. It is found that the spin relaxation consists of three stages (in some cases, two) -an initial D'yakonov-Perel' relaxation is followed by spin helix formation and its subsequent decay. Analytical expressions for the decay time are found. We support our analytical results by results of Monte Carlo simulations. Dynamics of electron spin polarization in semiconductor structures has attracted a lot of attention recently in the context of spintronics 1-3 , which is playing a fundamental role in the novel technological developments based on different effects in this scientific area. Moreover, the ability to understand and predict the dynamics of electron spins in semiconductors is also important for the area of two terminal electronic devices with memory, so-called memristive devices 4-8 . In some of them 4,6 , the electron spin degree of freedom defines their internal state and, consequently, is responsible for their time-dependent memory response.It has been shown by us recently 9-11 that the system boundaries significantly modify the dynamics of process. For example, we have demonstrated 10 that in finite size 2D systems, the spin polarization density decays much slower than in the bulk and the exponential spin polarization decay rate is defined by both the system size and strength of spin-orbit interaction. In finite length wires 9 and channels 11 (oriented in a specific direction), changes in the electron spin relaxation are even more pronounced: instead of relaxing to zero, the homogeneous electron spin polarization relaxes into a persistent spin polarization structure known as the spin helix 12-15 -a spin polarization configuration in which the direction of spin polarization density rotates along the wire.In real experimental situations, the spin helix configuration can not exist infinitely long. Here, we assume that the main decay mechanism is due to spin relaxation at system boundaries. Indeed, local strong random electric fields in the vicinity of boundaries result in a random spin-orbit interaction influencing the electron spin degree of freedom. It is thus important to develop a theory and model spin relaxation in constrained geometries taking into account the boundary spin relaxation and understand how the boundary spin relaxation changes the overall character of electron spin relaxation in the entire system.In this paper, we use both spin kinetic 11 and diffusion [15][16][17][18][19] equations to investigate the dynamics of electron spin polarization in semiconductor ...
Disorder plays a crucial role in spin dynamics in solids and condensed matter systems. We demonstrate that for a spin-orbit coupled Bose-Einstein condensate in a random potential two mechanisms of spin evolution, that can be characterized as "precessional" and "anomalous", are at work simultaneously. The precessional mechanism, typical for solids, is due to the condensate displacement. The unconventional "anomalous" mechanism is due to the spin-dependent velocity producing the distribution of the condensate spin polarization. The condensate expansion is accompanied by a random displacement and fragmentation, where it becomes sparse, as clearly revealed in the spin dynamics. Thus, different stages of the evolution can be characterized by looking at the condensate spin. Bose-Einstein condensates (BECs) of (pseudo)spin-1/2 particles provide novel opportunities for visualizing unconventional phenomena extensively studied experimentally (e.g. [4][5][6][7]) and theoretically (e.g. [8][9][10][11][12][13][14][15][16]).In the presence of SOC, the spin of a particle rotates with a rate dependent on the particle's momentum. In disordered solids, randomization of momentum leads to the Dyakonov-Perel mechanism of spin relaxation [17] in macroscopic ensembles. Studies of BEC spin dynamics in a random potential are strongly different from those in solids in the following aspects: (i) one can access the evolution of a single wavepacket; (ii) one can study the effects of the anomalous spin-dependent velocity [18] in different regimes of disorder and SOC, and (iii) the spin dynamics of a BEC is influenced by interatomic interactions inside each wavepacket, which are impossible for electrons. Here we investigate these qualitatively new, unobservable in solids, effects in the spin evolution of a quasi one-dimensional Bose-Einstein condensate. Usually, one is interested in the long time behavior, where localization takes over [19][20][21][22][23][24][25][26][27]. In the presence of SOC, the localization was studied in Ref. [28]. Motivated by the fact that the evolving spin density is well-defined for the experimental observation only at short time intervals, we consider here the initial stage of the evolution.We consider a SOC condensate tightly confined in the transverse directions to produce a quasi one-dimensional system, subject to a random optical field producing a disorder potential U rnd (x). The two-component wave function Ψ(x, t) ≡ [ψ ↑ (x, t), ψ ↓ (x, t)] T , characterizing the spin 1/2 system with the density |Ψ| 2 = |ψ ↑ (x, t)| 2 + |ψ ↓ (x, t)| 2 normalized to the total number of particles N ≫ 1, is obtained as a solution of the nonlinear Schrödinger equation i ∂ t Ψ = H(t)Ψ. The effective Hamiltonian:includes the interatomic interaction in the GrossPitaevskii form [29,30] with the dimensionless constant g [31]. Here M is the particle mass and the frequency of the trap ω(t ≤ 0) = ω 0 , ω(t > 0) = 0 corresponds to a sudden switch off. The energy quantum ω 0 and the length a ho = /M ω 0 represent the natural scales for th...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.