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Register a new userAll-electrical time-resolved spin generation and spin manipulation in n-InGaAs
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We demonstrate all-electrical spin generation and subsequent manipulation by two successive electric field pulses in an n-InGaAs heterostructure in a time-resolved experiment at zero external magnetic field. The first electric field pulse along the $[1bar10]$ crystal axis creates a current induced spin polarization (CISP) which is oriented in the plane of the sample. The subsequent electric field pulse along [110] generates a perpendicular magnetic field pulse leading to a coherent precession of this spin polarization with 2-dimensional electrical control over the final spin orientation. Spin precession is probed by time-resolved Faraday rotation. We determine the build-up time of CISP during the first field pulse and extract the spin dephasing time and internal magnetic field strength during the spin manipulation pulse.
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Spin waves (SWs), the collective precessional motion of spins in a magnetic system, have been proposed as a promising alternative system with low-power consumption for encoding information. Spin Hall nano-oscillator (SHNO), a new-type spintronic nano-device, can electrically excite and control spin waves in both nanoscale magnetic metals and insulators with low damping by the spin current due to spin Hall effect. Here, we will review recent progress about spin-wave excitation and experimental parameters dependent spectrum in SHNOs. The nanogap SHNOs based on in-plane magnetization Py/Pt exhibits a nonlinear self-localized bullet soliton localized at the center of the gap between the electrodes and a secondary high-frequency mode which coexists with the primary bullet mode at higher currents. While in the nanogap SHNOs with strong perpendicular magnetic anisotropy (PMA), besides both nonlinear bullet soliton and propagating spin-wave mode are achieved and controlled by varying the external magnetic field and current, the magnetic bubble skyrmion mode also can be excited at a low in-plane magnetic field. These SW modes show thermal-induced mode hopping behavior at high temperature due to the coupling between modes mediated by thermal-magnon-mediated scattering. Moreover, thanks to PMA-induced effective field, a single coherent mode also can be achieved without applying an external magnetic field. The strong nonlinear effect of spin-waves makes SHNOs easy to achieve synchronization with external microwave signals or mutual synchronization between multiple oscillators with improving the coherence and power of oscillation modes significantly. Spin-waves in SHNOs with an external free magnetic layer have a wide range of applications from as a nanoscale signal source of low-power consumption magnonic devices to spin-based neuromorphic computing systems in the field of artificial intelligence.
Electrical generation of THz spin waves is theoretically explored in an antiferromangetic nanostrip via the current-induced spin-orbit torque. The analysis based on micromagnetic simulations clearly illustrates that the Neel-vector oscillations excited at one end of the magnetic strip can propagate in the form of a traveling wave when the nanostrip axis aligns with the magnetic easy-axis. A sizable threshold is observed in the driving current density or the torque to overcome the unfavorable anisotropy as expected. The generated spin waves are found to travel over a long distance while the angle of rotation undergoes continuous decay in the presence of non-zero damping. The oscillation frequency is tunable via the strength of the spin-orbit torque, reaching the THz regime. Other key characteristics of the spin waves such as the phase and the chirality can also be modulated actively. The simulation results further indicate the possibility of wave-like superposition between the excited spin oscillations, illustrating its application as an efficient source of spin-wave signals for information processing.
To mitigate climate change, our global society is harnessing direct (solar irradiation) and indirect (wind/water flow) sources of renewable electrical power generation. Emerging direct sources include current-producing thermal gradients in thermoelectric materials, while quantum physics-driven processes to convert quantum information into energy have been demonstrated at very low temperatures. The magnetic state of matter, assembled by ordering the electrons quantum spin property, represents a sizeable source of built-in energy. We propose to create a direct source of electrical power at room temperature (RT) by utilizing magnetic energy to harvest thermal fluctuations on paramagnetic (PM) centers. Our spin engine rectifies current fluctuations across the PM centers spin states according to the electron spin by utilizing so-called spinterfaces with high spin polarization. As a rare experimental event, we demonstrate how this path can generate 0.1nW at room temperature across a 20 micron-wide spintronic device called the magnetic tunnel junction, assembled using commonplace Co, C and MgO materials. The presence of this path in our experiment, which also generates very high spintronic performance, is confirmed by analytical and ab-initio calculations. Device downscaling, and the ability for other materials systems than the spinterface to select a transport spin channel at RT widens opportunities for routine device reproduction. The challenging control over PM centers within the tunnel barriers nanotransport path may be addressed using oxide- and organic-based nanojunctions. At present densities in MRAM products, this spin engine could lead to always-on areal power densities well beyond that generated by solar irradiation on earth. Further developing this concept can fundamentally alter our energy-driven societys global economic, social and geopolitical constructs.
The demand for compact, high-speed and energy-saving circuitry urges higher efficiency of spintronic devices that can offer a viable alternative for the current electronics. The route towards this goal suggests implementing two-dimensional (2D) materials that provide large spin polarization of charge current together with the long-distance transfer of the spin information. Here, for the first time, we experimentally demonstrate a large spin polarization of the graphene conductivity ($approx 14%$) arising from a strong induced exchange interaction in proximity to a 2D layered antiferromagnetic. The strong coupling of charge and spin currents in graphene with high efficiency of spin current generation, comparable to that of metallic ferromagnets, together with the observation of spin-dependent Seebeck and anomalous Hall effects, all consistently confirm the magnetic nature of graphene. The high sensitivity of spin transport in graphene to the magnetization of the outermost layer of the adjacent interlayer antiferromagnet, also provides a tool to read out a single magnetic sub-lattice. The first time observations of the electrical and thermal generation of spin currents by magnetic graphene suggest it as the ultimate building block for ultra-thin magnetic memory and sensory devices, combining gate tunable spin-dependent conductivity, long-distance spin transport and spin-orbit coupling all in a single 2D material.
We propose a method to electrically control electron spins in donor-based qubits in silicon. By taking advantage of the hyperfine coupling difference between a single-donor and a two-donor quantum dot, spin rotation can be driven by inducing an electric dipole between them and applying an alternating electric field generated by in-plane gates. These qubits can be coupled with exchange interaction controlled by top detuning gates. The qubit device can be fabricated deep in the silicon lattice with atomic precision by scanning tunneling probe technique. We have combined a large-scale full band atomistic tight-binding modeling approach with a time-dependent effective Hamiltonian description, providing a design with quantitative guidelines.
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