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. TassAbstract: 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
