Sergey Smirnov, Dario Bercioux, Milena Grifoni, Klaus Richter
备注：
4 pages, 3 figures, physical explanation of the results was added, role of the spin torque is now mentioned, Fig. 2 was changed: only the non-equilibrium spin current (the full spin current was removed) is now shown but for different dissipation intensity
We predict the possibility to generate a finite stationary spin current by applying an unbiased ac driving to a quasi-one-dimensional asymmetric periodic structure with Rashba spin-orbit interaction and strong dissipation. We show that under a finite coupling strength between the orbital degrees of freedom the electron dynamics at low temperatures exhibits a pure spin ratchet behavior, {\it i.e.} a finite spin current and the absence of charge transport in spatially asymmetric structures. It is also found that the equilibrium spin currents are not destroyed by the presence of strong dissipation.
We demonstrate transport rectification in a hermitian Hamiltonian quantum ratchet by a dissipative, dynamic impurity. While the bulk of the ratchet supports transport in both directions, the properly designed loss function of the local impurity acts as a direction-dependent filter for the moving states. We analyse this scheme theoretically by making use of Floquet-S-Matrix theory. In addition, we provide the direct experimental observation of one-way transmittance in periodically modulated plasmonic waveguide arrays containing a local impurity with engineered losses.
It is of considerable technological importance to achieve an electrical control of magnetism of sufficient magnitude. To overcome the in-plane shape anisotropy, needed is the electrical control of a perpendicular magnetic anisotropy (PMA). It is known, within a free electron model, the Rashba spin-orbit coupling provides such a control. Surprisingly, this same Rashba PMA is enhanced by two to three orders of magnitude when a periodic potential is added. Usually spin Berry phase physics reflects time dependent magnetic fields. Here it is shown, within a time independent model, such physics aris…
Two-dimensional systems with Rashba spin-orbit coupling are not Galilean invariant and therefore electron--electron collisions in them may affect the current. However when taken alone, they cannot ensure a nonzero dc resistivity, so their effects are masked by impurity scattering. Here we calculate the related finite-frequency response and show that the electron--electron scattering in clean Rashba conductors decreases the Drude weight while resulting in a finite dissipative component of the response outside of the Drude peak.
Magnetization dynamics in single-domain ferromagnets can be triggered by charge current if spin-orbit coupling is sufficiently strong. We apply functional Keldysh theory to investigate Rashba spin-orbit torques in metallic two-dimensional ferromagnets. A reactive, anti-damping-like spin-orbit torque as well as a dissipative, field-like torque are calculated microscopically, to the leading order in the spin-orbit interaction strength. By calculating the first vertex correction we show that the intrinsic anti-damping-like torque vanishes unless the scattering rates are spin-dependent.
The spin-galvanic (inverse Edelstein) and inverse spin-Hall effects are calculated for a hybrid system that combines thin superconductor and Rashba-metal layers. These effects are produced by a nonequilibrium spin polarization which is injected into the normal metal layer. This polarization gives rise to an electric potential that relaxes within some characteristic length, which is determined by Andreev reflection. Within this length the dissipative electric current of quasiparticles in the normal layer converts into the supercurrent. This process involves only subgap states and at low tempera…
Describing current in open quantum systems can be problematic due to the subtle interplay of quantum coherence and environmental noise. Probing the noise-induced current can be detrimental to the tunneling-induced current and vice versa. We derive a general theory for the probability current in quantum systems arbitrarily interacting with their environment that overcomes this difficulty. We show that the current can be experimentally measured by performing a sequence of weak and standard quantum measurements. We exemplify our theory by analyzing a simple Smoluchowski-Feynman-type ratchet consi…
We present a theoretical study of two-dimensional spatially and temporally varying magnetic textures in the presence of spin-orbit coupling (SOC) of both the Rashba and Dresselhaus types. We show that the effective gauge field due to these SOCs, contributes to the dissipative and reactive spin torques in exactly the same way as in electromagnetism. Our calculations reveal that Rashba (Dresselhaus) SOC induces a chiral dissipation in interfacial (bulk) inversion asymmetric magnetic materials. Furthermore, we show that in addition to chiral dissipation $α_c$, these SOCs also produce a chiral ren…
The Berry curvature involving time and momentum derivatives, which we term emergent electric field, induces a nondisspative current known as the adiabatic charge pumping or Thouless pumping in periodically driven systems. We study dissipative currents originated from the interplay between emergent electric fields and electric/magnetic fields in two and three dimensions on the basis of the Boltzmann transport theory. As an example of two-dimensional models, we study the Rashba Hamiltonian with time-dependent and anisotropic spin-orbit coupling. We show that the interplay between emergent electr…
We study the electrical conductance in single-mode quantum wires with Rashba spin-orbit interaction subjected to externally applied magnetic fields in the regime in which the ratio of spin-orbit momentum to the Fermi momentum is close to an odd integer, so that a combined effect of multi-electron interaction and applied magnetic field leads to a partial gap in the spectrum. We study how this partial gap manifests itself in the temperature dependence of the fractional conductance of the quantum wire. We use two complementing techniques based on bosonization: refermionization of the model at a p…
