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Register a new userSpin charge conversion in Rashba split ferromagnetic interfaces
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We show here theoretically and experimentally that a Rashba-split electron state inside a ferromagnet can efficiently convert a dynamical spin accumulation into an electrical voltage. The effect is understood to stem from the Rashba splitting but with a symmetry linked to the magnetization direction. It is experimentally measured by spin pumping in a CoFeB/MgO structure where it is found to be as efficient as the inverse spin Hall effect at play when Pt replaces MgO, with the extra advantage of not affecting the damping in the ferromagnet.
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At interfaces with inversion symmetry breaking, Rashba effect couples the motion of electrons to their spin; as a result, spin-charge interconversion mechanism can occur. These interconversion mechanisms commonly exploit Rashba spin splitting at the Fermi level by spin pumping or spin torque ferromagnetic resonance. Here, we report evidence of significant photoinduced spin to charge conversion via Rashba spin splitting in an unoccupied state above the Fermi level at the Cu(111)/$alpha$-Bi$_{2}$O$_{3}$ interface. We predict an average Rashba coefficient of $1.72times 10^{-10}eV.m$ at 1.98 eV above the Fermi level, by fully relativistic first-principles analysis of the interfacial electronic structure with spin orbit interaction. We find agreement with our observation of helicity dependent photoinduced spin to charge conversion excited at 1.96 eV at room temperature, with spin current generation of $J_{s}=10^{6}A/m^{2}$. The present letter shows evidence of efficient spin-charge conversion exploiting Rashba spin splitting at excited states, harvesting light energy without magnetic materials or external magnetic fields.
We show theoretically that conversion between spin and charge by spin-orbit interaction in metals occurs even in a non-local setup where magnetization and spin-orbit interaction are spatially separated if electron diffusion is taken into account. Calculation is carried out for the Rashba spin-orbit interaction treating the coupling with a ferromagnet perturbatively. The results indicate the validity of the concept of effective spin gauge field (spin motive force) in the non-local configuration. The inverse Rashba-Edelstein effect observed for a trilayer of a ferromagnet, a normal metal and a heavy metal can be explained in terms of the non-local effective spin gauge field.
In spintronic devices, the two main approaches to actively control the electrons spin degree of freedom involve either static magnetic or electric fields. An alternative avenue relies on the application of optical fields to generate spin currents, which promises to bolster spin-device performance allowing for significantly faster and more efficient spin logic. To date, research has mainly focused on the optical injection of spin currents through the photogalvanic effect, and little is known about the direct optical control of the intrinsic spin splitting. Here, to explore the all-optical manipulation of a materials spin properties, we consider the Rashba effect at a semiconductor interface. The Rashba effect has long been a staple in the field of spintronics owing to its superior tunability, which allows the observation of fully spin-dependent phenomena, such as the spin-Hall effect, spin-charge conversion, and spin-torque in semiconductor devices. In this work, by means of time and angle-resolved photoemission spectroscopy (TR-ARPES), we demonstrate that an ultrafast optical excitation can be used to manipulate the Rashba-induced spin splitting of a two-dimensional electron gas (2DEG) engineered at the surface of the topological insulator Bi$_{2}$Se$_{3}$. We establish that light-induced photovoltage and charge carrier redistribution -- which in concert modulate the spin-orbit coupling strength on a sub-picosecond timescale -- can offer an unprecedented platform for achieving all optically-driven THz spin logic devices.
We study spin-polarized quasiparticle transport in a mesoscopic superconductor with a spin- splitting field in the presence of co-flowing supercurrent. In such a system, the nonequilibrium state is characterized by charge, spin, energy and spin energy modes. Here we show that in the presence of both spin splitting and supercurrent, all these modes are mutually coupled. As a result, the supercurrent can convert charge imbalance, that in the presence of spin splitting decays on a relatively short scale, to a long-range spin accumulation decaying only via inelastic scattering. This effect enables coherent charge-spin conversion controllable by a magnetic flux, and it can be detected by studying different symmetry components of the nonlocal conductance signal.
We evaluate the non-equilibrium spin polarization induced by an applied electric field for a tight-binding model of electron states at oxides interfaces in LAO/STO heterostructures. By a combination of analytic and numerical approaches we investigate how the spin texture of the electron eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry determines the sign of the induced spin polarization as a function of the chemical potential or band filling, both in the absence and presence of local disorder. With the latter, we find that the induced spin polarization evolves from a non monotonous behavior at zero temperature to a monotonous one at higher temperature. Our results may provide a sound framework for the interpretation of recent experiments.
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