Spin evolution of cold atomic gases in SU(2)⊗\otimes U(1) fields

We consider response function and spin evolution in spin-orbit coupled cold atomic gases in a synthetic gauge magnetic field influencing solely the orbital motion of atoms. We demonstrate that various regimes of spin-orbit coupling strength, magnetic field, and disorder can be treated within a single approach based on the representation of atomic motion in terms of auxiliary collective classical trajectories. Our approach allows for a unified description of fermionic and bosonic gases.Comment: 8 pages, 2 figure

Duality of the spin and density dynamics for two-dimensional electrons with a spin-orbit coupling

We study spin dynamics in a two-dimensional electron gas with a pure gauge non-Abelian spin-orbit field, for which systems with balanced Rashba and Dresselhaus spin-orbit couplings, and the (110)-axis grown GaAs quantum wells are typical examples. We demonstrate the duality of the spin evolution and the electron-density dynamics in a system without spin-orbit coupling, which considerably simplifies and deepens the analysis of spin-dependent processes. This duality opens a venue for the understanding of this class of systems, highly interesting for their applications in spintronics, through known properties of the systems without spin-orbit coupling.Comment: version accepted to PRB, revtex4, 4+ pages, 1 figur

Diffusive and precessional spin dynamics in a two-dimensional electron gas with disorder: a gauge theory view

We develop a gauge theory for diffusive and precessional spin dynamics in two-dimensional electron gas with disorder. Our approach reveals a direct connections between the absence of the equilibrium spin current and strong anisotropy in the spin relaxation: both effects arise if the spin-orbit coupling is reduced to a pure gauge SU(2) field. In this case, by a gauge transformation in the form of a local SU(2) rotation in the spin subspace the spin-orbit coupling can be removed. The resulting spin dynamics is exactly described in terms of two kinetic coefficients: the spin diffusion and electron mobility. After the inverse transformation, full diffusive and precessional spin density dynamics, including the anisotropic spin relaxation, formation of stable spin structures, and spin precession induced by a macroscopic current, is restored. Explicit solutions of the spin evolution equations are found for the initially uniform spin density and for stable nonuniform structures. Our analysis demonstrates a universal relation between the spin relaxation rate and spin diffusion coefficient.Comment: published version, minor correction

Spin dephasing and pumping in graphene due to random spin-orbit interaction

We consider spin effects related to the random spin-orbit interaction in graphene. Such a random interaction can result from the presence of ripples and/or other inhomogeneities at the graphene surface. We show that the random spin-orbit interaction generally reduces the spin dephasing (relaxation) time, even if the interaction vanishes on average. Moreover, the random spin-orbit coupling also allows for spin manipulation with an external electric field. Due to the spin-flip interband as well as intraband optical transitions, the spin density can be effectively generated by periodic electric field in a relatively broad range of frequencies.Comment: 9 pages, 7 figure

Spin relaxation and combined resonance in two-dimensional electron systems with spin-orbit disorder

Disorder in spin-orbit (SO) coupling is an important feature of real low-dimensional electron structures. We study spin relaxation due to such a disorder as well as resulting abilities of spin manipulation. The spin relaxation reveals quantum effects when the spatial scale of the randomness is smaller than the electron wavelength. Due to the disorder in SO coupling, a time-dependent external electric field generates a spatially random spin-dependent perturbation. The resulting electric dipole spin resonance in a two-dimensional electron gas leads to spin injection in a frequency range of the order of the Fermi energy. These effects can be important for possible applications in spintronics.Comment: 4 pages, 3 figure

Physical Limits of the ballistic and non-ballistic Spin-Field-Effect Transistor: Spin Dynamics in Remote Doped Structures

We investigate the spin dynamics and relaxation in remotely-doped two dimensional electron systems where the dopants lead to random fluctuations of the Rashba spin-orbit coupling. Due to the resulting random spin precession, the spin relaxation time is limited by the strength and spatial scale of the random contribution to the spin-orbit coupling. We concentrate on the role of the randomness for two systems where the direction of the spin-orbit field does not depend on the electron momentum: the spin field-effect transistor with balanced Rashba and Dresselhaus couplings and the (011) quantum well. Both of these systems are considered as promising for the spintronics applications because of the suppression of the Dyakonov-Perel' mechanism there makes the realization of a spin field effect transistor in the diffusive regime possible. We demonstrate that the spin relaxation through the randomness of spin-orbit coupling imposes important physical limitations on the operational properties of these devices.Comment: 10 pages, 4 figure

Fast and robust spin manipulation in a quantum dot by electric fields

We apply an invariant-based inverse engineering method to control by time-dependent electric fields electron spin dynamics in a quantum dot with spin-orbit coupling in a weak magnetic field. The designed electric fields provide a shortcut to adiabatic processes that flips the spin rapidly, thus avoiding decoherence effects. This approach, being robust with respect to the device-dependent noise, can open new possibilities for the spin-based quantum information processing.Comment: 7 pages, 6 figures, with supplemental material. Errors in the published version have been correcte