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Non-Equilibrium Green's Function based Circuit Models for Coherent Spin Devices
摘要： With recent developments in spintronics, it is now possible to envision 'spin-driven' devices with magnets and interconnects that require a new class of transport models using generalized Fermi functions and currents, each with four components: one for charge and three for spin. The corresponding impedance elements are not pure numbers but 4 × 4 matrices. Starting from the Non-Equilibrium Green's Function (NEGF) formalism in the elastic, phase-coherent transport regime, we develop spin generalized Landauer-Büttiker formulas involving such 4 × 4 conductances, for multi-terminal devices in the presence of Normal-Metal (NM) leads. In addition to usual 'terminal' conductances describing currents at the contacts, we provide 'spin-transfer torque' conductances describing the spin currents absorbed by ferromagnetic (FM) regions inside the conductor, specifying both of these currents in terms of Fermi functions at the terminals. We derive universal sum rules and reciprocity relations that would be obeyed by such matrix conductances. Finally, we apply our formulation to two example Hamiltonians describing the Rashba and the Hanle effect in 2D. Our results allows the use of pure quantum transport models as building blocks in constructing circuit models for complex spintronic and nano-magnetic structures and devices for simulation in SPICE-like simulators.
关键词： Rashba effect,spintronics,Landauer-Büttiker formula,spin-transfer torque,Non-Equilibrium Green's Function,Hanle effect,SPICE simulation
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - FANTASI: A Novel Devices-to-Circuits Simulation Framework for Fast Estimation of Write Error Rates in Spintronics
摘要： Though physical mechanisms such as spin-transfer torque (STT), spin-orbit torque (SOT), and voltage-controlled magnetic anisotropy (VCMA) has potential to enable energy-efficient and ultra-fast switching of spintronic devices, the switching dynamics are stochastic due to thermal fluctuations. Thus, there is a need in spintronics to understand the interactions between circuit design and the error rate in the switching mechanism, called as write error rate. In this paper, we propose a novel devices-to-circuits simulation framework (FANTASI) for fast estimation of the write error rates (WER) in different spintronic devices and circuits. Here, we show that, FANTASI enables efficient spintronic device-circuit co-design, with results in good agreement with the experimental measurements.
关键词： Fokker-Planck equation,spin-orbit torque,Spin-transfer torque,voltage-controlled magnetic anisotropy,spintronics
更新于2025-09-23 15:22:29
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Domain wall dynamics due to femtosecond laser-induced superdiffusive spin transport
摘要： Manipulation of magnetic domain walls via a helicity-independent laser pulse has recently been experimentally demonstrated and various physical mechanisms leading to domain wall dynamics have been discussed. Spin-dependent superdiffusive transport of hot electrons has been identified as one of the possible ways to affect a magnetic domain wall. Here, we develop a model based on superdiffusive spin-dependent transport to study the laser-induced transport of hot electrons through a smooth magnetic domain wall. We show that the spin transfer between neighboring domains can enhance ultrafast demagnetization in the domain wall. More importantly, our calculations reveal that when the laser pulse is properly focused onto the vicinity of the domain wall, it can excite sufficiently strong spin currents to generate a spin-transfer torque that can rapidly move the magnetic domain wall by several nanometers in several hundred femtoseconds, leading to a huge nonequilibrium domain wall velocity.
关键词： spin-transfer torque,ultrafast demagnetization,magnetic domain walls,superdiffusive spin transport,laser-induced dynamics
更新于2025-09-23 15:21:01
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Emerging Memory Modeling Challenges (Invited Paper)
摘要： Emerging Memory (EM) is a broad class of memory devices leveraging a wide spectrum of physical phenomena and/or material properties, that go beyond the charge storage concept of more conventional NAND and DRAM technologies. Availability of physical models and simulation tools to understand their behavior, predict performance, engineer materials and cell architecture would be extremely useful for their successful development. However, such tools are not always available because of the diversity and complexity of the physical mechanisms. This paper would like to review the main trends of the on-going modeling and simulation activities in the field of EM, trying to point out what are the needs and challenges for the future.
关键词： Modeling,Phase Change Memory,Simulation,Resistive RAM,Emerging Memory,Spin Transfer Torque Magnetic RAM
更新于2025-09-04 15:30:14