Habituation based synaptic plasticity and organismic learning in a quantum perovskite

Abstract

A central characteristic of living beings is the ability to learn from and respond to their environment leading to habit formation and decision making. This behavior, known as habituation, is universal among all forms of life with a central nervous system, and is also observed in single-cell organisms that do not possess a brain. Here, we report the discovery of habituation-based plasticity utilizing a perovskite quantum system by dynamical modulation of electron localization. Microscopic mechanisms and pathways that enable this organismic collective charge-lattice interaction are elucidated by first-principles theory, synchrotron investigations, ab initio molecular dynamics simulations, and in situ environmental breathing studies. We implement a learning algorithm inspired by the conductance relaxation behavior of perovskites that naturally incorporates habituation, and demonstrate learning to forget: a key feature of animal and human brains. Incorporating this elementary skill in learning boosts the capability of neural computing in a sequential, dynamic environment.

Electron‐Doping Mottronics in Strongly Correlated Perovskite

“…In previous reports, the hydrogenation is (first, i.e., at low H concentrations) expected to trigger a sharp electronic phase transition of the SmNiO 3 from the electron itinerant t e 2g 6 g 1 state to the electron localized t e 2g 6 g 2 state [1,2,4,5] to open a wider bandgap (the extra electrons fill into the p-d hybridized orbits with strong p character since perovskite nickelates carry strong covalency; whether this is a negative or positive transfer insulator [11,12] does not change the characteristic proposed here). Now, what happens if the SmNiO 3 is doped with higher concentration of hydrogen?…”

“…[7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e www.advmat.de www.advancedsciencenews.com state. [1][2][3][4][5] This was reported to sharply increase the electronic resistivity by several orders of magnitude, [1,2,4,5] while hydrogenated SmNiO 3 is expected to be proton conductive. [4] Although a considerable understanding of the transport properties has been established for single crystalline H x SmNiO 3 (Ni 2+ t e 2g 6 g 2 ) and other proton-doped correlated materials, it remains entirely unclear how doping-controlled transport properties behave in the presence of interfaces and microstructure.…”

“…Now, what happens if the SmNiO 3 is doped with higher concentration of hydrogen? [1,2,4,5] The grain boundaries within the heterostructure are hydrogen aggregation locations, and can behave as migration channels for protons when a sufficiently large negative bias voltage (V Ext ) is applied to the platinum (Pt) electrode. [8] Combining such a hydrogen doping with electronic field regulation in hydrogenated Pt/ H x SmNiO 3 /SrRuO 3 polycrystalline heterostructures should thus make it possible to realize electronic diode behavior.…”

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Hydrogen (proton) induced switchable multiphase transformations in d-band electron-correlated materials recently opened a new field for exploring merging multifunctional proton-gated electronic devices, [1] synaptic plasticity, [2,3] sensors, [4] and novel energy conversion devices. [5] Compared to other dopant elements, hydrogen is small in radius and has high ionic mobility.

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“…[1,[4][5][6] Therefore, the proton distribution is highly adjustable via external electric fields, and the respective tuning of the physical properties of materials is feasible. This is, in particular, the case for the hydrogen-induced sharp transitions in electron orbital configurations and the magnetoelectric/spintronic states for d-band electron-correlated materials, such as SmNiO 3 , [1][2][3][4][5] SrCoO 3−δ , [6] and VO 2 . [7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e 2g 6 g 1 state to the electron-localized Ni 2+ t e 2g 6 g 2 The discovery of hydrogen-induced electron localization and highly insulating states in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g., Mottronics).…”