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Monday, July 20 • 8:00pm - 9:00pm
P198: Voltage-Dependent Synaptic Plasticity in Magnetic Tunnel Junctions

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Note: This poster (#P198) will be presented by the second author (Mojtaba Madadi Asl) jointly with poster #P199.

Google Meet link: https://meet.google.com/exp-kbbg-vjp

Authors: Saeideh Ramezani Akbarabadi
, Mojtaba Madadi Asl, Peter A. Tass

Abstract: Spike-timing-dependent plasticity (STDP) is a fundamental learning mechanism that shapes plastic synaptic strengths in brain networks according to pre- and postsynaptic spike times. Later, a model of voltage-based STDP was proposed based on the postsynaptic membrane potential to explain experimentally observed connectivity patterns in cortex. Synaptic plasticity plays a key role in memory retention by modulating functional cortical circuitry in memory networks. The development of solid-state devices in recent years provided a means for computational implementation and experimental realization of neuromorphic structures designed to emulate adaptive behavior of synapses in brain. Particularly, spin-polarized transport through magnetic tunnel junctions (MTJs) is a well-characterized mechanism for the implementation of learning process due to the rapid and high-density information storage capabilities of MTJs as a memory device [1]. Previously, it has been shown that the emergent synaptic structure between a pair of neurons characterized by two reciprocally coupled synapses with STDP can be theoretically predicted by the effective synaptic strength in the two-neuron motif, i.e. the ratio of relative synaptic strengths to their sum [2]. In this study, we considered a two-terminal single-molecule MTJ that consists of two ferromagnetic (FM) cobalt electrodes separated by a phenyl dithiol (PDT) molecule and investigated transport properties using a non-equilibrium Green's function (NEGF) formalism. By introducing an effective spin-polarized tunneling conductance, i.e. the ratio of relative conductances in parallel (P) and anti- parallel (AP) configurations to their sum, we show that the change in the two- component conductance crucially depends on the bias voltage applied to the MTJ where its behavior is reminiscent of the classical STDP .

References: For more information on the background, take a look at our related publications:

1. Study of length-dependent tunneling magnetoresistance in two phenyl based molecules: https://benthamscience.com/journals/current-physical-chemistry/volume/4/issue/3/page/285/

2. Delay-induced multistability and loop formation in neuronal networks with spike-timing-dependent plasticity: https://www.nature.com/articles/s41598-018-30565-9

Speakers
avatar for Saeideh Ramezani Akbarabadi

Saeideh Ramezani Akbarabadi

Researcher, Department of Physics, University of Guilan
Saeideh Ramezani Akbarabadi studied physics at the Department of Physics, University of Guilan, Rasht, Iran. Saeideh does research in condensed matter physics, molecular electronics, nanophysics and chemical physics. They investigate the effect of different parameters such as contact... Read More →



Monday July 20, 2020 8:00pm - 9:00pm CEST
Slot 08