The brain has the ability to learn and evaluate as it receives and registers information. Signals between neurons are transmitted via synapses whose plasticity is modulated by usage. A bio-realistic electrical analog is a second-order memristor, where the short-term internal dynamics influence the long-term state. It is achieved here with an all-oxide multiferroic tunnel junction: La_0.7Sr_0.3MnO₃ / BaTiO₃ / La_0.7Sr_0.3MnO₃. Similar to the modulation of synaptic weight by stimuli, multi-levels of resistance may be encoded by mean of voltage pulses, on long time scale and in correlation with short-term effects. Neuromimetic learning functions are demonstrated: short and long-term potentiation/depression, paired-pulse facilitation/depression, spike-rate- and experience-dependent plasticity. The threshold frequency of pulse trains at which depression changes into potentiation depends on the previous activity, with a sliding effect as in neurobiology. The voltage pulses induce reversible changes of both dielectric polarization and oxygen vacancies distribution, generating transient trapped/detrapped charges at the two interfaces that govern the dynamic response. The resistance levels are determined by the final cationic ordering (the redox Mn³⁺/Mn⁴⁺ ratio) at the two interfacial layers. The stimulation/relaxation dynamics are close to that in biological counterparts. Such memristors can be used in hardware artificial networks for advanced processing/storage of the information.

中文翻译：

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基于全氧化物多铁隧道结的二阶忆阻器用于突触的仿生仿真

大脑在接收和记录信息时具有学习和评估的能力。神经元之间的信号通过突触传递，突触的可塑性受到使用的调节。仿生电模拟是二阶忆阻器，其中短期内部动态影响长期状态。这是通过全氧化物多铁性隧道结实现的：La _0.7 Sr _0.3 MnO ₃ / BaTiO ₃ / La _0.7 Sr _0.3 MnO ₃. 与刺激对突触重量的调制类似，多级电阻可以通过电压脉冲进行编码，在长时间范围内并与短期效应相关。展示了拟神经学习功能：短期和长期增强/抑制、配对脉冲促进/抑制、尖峰率和经验依赖性可塑性。抑郁转变为增强的脉冲序列的阈值频率取决于先前的活动，具有神经生物学中的滑动效应。电压脉冲引起介电极化和氧空位分布的可逆变化，在控制动态响应的两个界面处产生瞬态俘获/去俘获电荷。电阻水平由最终的阳离子排序（氧化还原 Mn ³⁺/Mn ⁴⁺比率）在两个界面层。刺激/放松动力学接近生物学对应物。这种忆阻器可用于硬件人工网络中，用于信息的高级处理/存储。