KEYWORDS: Transistors, Stochastic processes, Resistance, Field effect transistors, Magnetism, Design, Simulations, Magnetic tunnel junctions, Molybdenum, Control systems
For certain applications such as in Artificial Intelligence and neuromorphic computing, modern computing schemes can require prohibitively large circuit- and energy-footprints. Probabilistic computing offers an alternative approach that seeks to exploit its inherently probabilistic nature to act as low-cost natural hardware accelerators for solving a range of complex problems from large-scale combinatorial optimization to Bayesian inference, and invertible Boolean logic. The base unit of probabilistic computing is known as the probabilistic bit, or p-bit, and requires tunable stochasticity; low-barrier Magnetic Tunnel Junctions (MTJs), in which the magnetization of the free layer fluctuates at room-temperature, are a natural spintronics-based solution for such high-quality random number generation and p-bit purposes. In this work, we present the experimental realization of a scaled p-bit core, integrating a stochastic in-plane MTJ with a novel multi-finger 2D-MoS2 transistor to achieve a compact spintronics-based p-bit platform that displays true randomness and a high degree of voltage-tunable stochasticity.
The transport properties of W-doped thermochromic V1-xWxO2 (x=0 and 0.0074) thin films prepared by pulsed laser deposition were studied to understand the effect of doping on the electrical properties of these films. Temperature dependent magneto-transport measurements (Hall effect) in magnetic fields up to 9 Tesla were performed on thin film vanadium dioxide (VO2) across the Mott metal-insulator transition (MIT). The Hall carrier density increases by 4 orders of magnitude at MIT. The Hall mobility varies little across the MIT and remains low at ~ 0.05 cm2 /V sec. The majority carriers are electrons. Magneto-resistance is small and positive. Comparison of the three Hall parameters including carrier concentration, conductivity and mobility between various doping levels on both metallic and insulating state are reported and a model has been proposed. A correlation between carrier concentration and conductivity of VO2 films is observed but doesn’t exist between carrier concentration and mobility.
Quantum-classical spin hybrids composed of physical system with complimentary characteristics have enabled novel capabilities and functionalities within the realm of existing technology. One half of such hybrid systems is the quantum impurity spin with small spin quantum number such that its description is governed by the counter-intuitive laws of quantum mechanics. The other is a classical magnet with large spin quantum number such that its dynamics can be captured within the framework of classical physics. Such hybrids give rise to possibilities where controlling the degrees of freedom in one system can be leveraged to control dynamics in the other. Leveraging the demonstrated spintronic tools of classical magnet dynamics, we demonstrate two significant steps towards realizing a quantum network for information processing applications. One, a theoretically designed regime where electrical control of non-linear magnetization dynamics of a nanomagnet provides a local, coherent, and low-power drive to manipulate a coupled quantum impurity spin without introducing additional decoherence. Another, where we demonstrate via a joint theoretical and experimental effort, the electrical tuning of interaction between electrically-controlled propagating magnons in an extended magnet and a quantum impurity spin. The merits of such a hybrid system provide pathways to overcome the bottlenecks associated with local controllability of individual quantum spins in a quantum network and modulate the interaction mediating the two subsystems.
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