Non-adiabatic generation of a pure spin current in a 1D quantum ring with spin-orbit interaction

We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a non-adiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal dephasing angle $\phi$. The stationary solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and used to calculate the time-dependent charge and spin currents. We find that there are critical values of $\phi$ at which the charge current disappears, while the spin current reaches a maximum or a minimum value.Comment: 8 pages, 5 figure

Electron-Dephasing Time in a Two-Dimensional Spin-Polarized System with Rashba Spin-Orbit Interaction

We calculate the dephasing time Bof an electron in a two-dimensional system with a Rashba spin-orbit interaction, spin-polarized by an arbitrarily large magnetic field parallel to the layer. B is estimated from the logarithmic corrections to the conductivity within a perturbative approach that assumes weak, isotropic disorder scattering. For any value of the magnetic field, the dephasing rate changes with respect to its unpolarized-state value by a universal function whose parameter is 2EZ=ESOI (EZ is the Zeeman energy, while ESOI is the spin-orbit interaction), confirming the experimental report published in Phys. Rev. Lett. 94, 186805 (2005). In the high-field limit, when 2EZ ESOI, the dephasing rate saturates and reaches asymptotically to a value equal to half the spin-relaxation rate

Closed-form weak localization magnetoconductivity in quantum wells with arbitrary Rashba and Dresselhaus spin-orbit interactions

We derive a closed-form expression for the weak localization (WL) corrections to the magnetoconductivity of a 2D electron system with arbitrary Rashba $\alpha$ and Dresselhaus $\beta$ (linear) and $\beta_3$ (cubic) spin-orbit interaction couplings, in a perpendicular magnetic field geometry. In a system of reference with an in-plane $\hat{z}$ axis chosen as the high spin-symmetry direction at $\alpha = \beta$, we formulate a new algorithm to calculate the three independent contributions that lead to WL. The antilocalization is counterbalanced by the term associated with the spin-relaxation along $\hat{z}$, dependent only on $\alpha - \beta$. The other term is generated by two identical scattering modes characterized by spin-relaxation rates which are explicit functions of the orientation of the scattered momentum. Excellent agreement is found with data from GaAs quantum wells, where in particular our theory correctly captures the shift of the minima of the WL curves as a function of $\alpha/\beta$. This suggests that the anisotropy of the effective spin relaxation rates is fundamental to understanding the effect of the SO coupling in transport.Comment: 5 pages, 2 figure

The Spin Mass of an Electron Liquid

We show that in order to calculate correctly the {\it spin current} carried by a quasiparticle in an electron liquid one must use an effective "spin mass" $m_s$, that is larger than both the band mass, $m_b$, which determines the charge current, and the quasiparticle effective mass $m^*$, which determines the heat capacity. We present microscopic calculations of $m_s$ in a paramagnetic electron liquid in three and two dimensions, showing that the mass enhancement $m_s/m_b$ can be a very significant effect.Comment: 10 pages, 1 figur

Thermodynamic Limits of the Local Field Corrections in a Spin-Polarized Electron System

In a spin-polarized electron gas, the effect of the exchange ͑x͒ and correlation ͑c͒ interactions can be incorporated into the dynamic response functions through spin-dependent local-field corrections G␴ x,c(␻,qជ). We obtain the zero-frequency and long-wavelength limits of G␴ x,c(␻,qជ) by analyzing the connection between the macroscopic response function and the thermodynamic parameters of the system