发表机构
Indian Institute of Science Education and Research Kolkata; Centre for Nanoscience and Engineering, Indian Institute of Science（印度科学教育研究所加尔各答分校; 印度科学院纳米科学与工程中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出类朗道动力学框架，将莫特器件开关转变描述为鞍-结分岔，以丝宽为序参量预测一级相变，并通过VO2实验验证，为器件设计提供基础。
AI 中文摘要
相关氧化物在施加电压时可切换至低电阻状态，这使得这些绝缘体-金属转变材料成为忆阻器技术的有前景候选材料。VO2等材料中的开关现象源于热失控不稳定性，该不稳定性导致绝缘体内突然形成携带电流的热金属丝。我们从理论和实验两方面将这种偏压诱导的开关行为作为非线性动力学稳定性问题进行研究。我们构造了类朗道自由能的李雅普诺夫函数，以证明开态（“置位”）和关态（“复位”）转变均可描述为独立的鞍-结分岔。从热输运的反应-扩散方程出发，突发的回跳（复位）至绝缘态被系统地表述为平均场类朗道动力学，其中丝宽度扮演序参量的角色。该表述预测了一个突变的一级相变，伴随着有限宽度丝在电流控制的复位转变中的断裂。我们将该表述与VO2薄膜器件上的电学和光学显微镜实验进行了定量比较。多周期开关动力学实验进一步揭示了在初始电-空间形成阶段之后出现稳定的随机机制。除了建立一个可随时与各种反应-扩散场景中的不稳定性进行比较的跨学科动力学框架外，该工作还为基于莫特转变技术的理性设计与优化提供了预测性基础。
英文摘要
Correlated oxides can switch to a low-resistance state when exposed to a voltage, making these insulator-to-metal transition materials promising candidates for memristor technology. Switching in materials such as VO2 occurs because of a thermal-runaway instability that leads to the abrupt formation of a hot current-carrying metallic filament within the insulator. We study, theoretically and experimentally, this bias-induced switching as a non-linear dynamics stability problem. We construct Landau free energy-like Lyapunov functions to show that both the on-state ("set") and the off-state ("reset") transitions can be described as separate saddle-node bifurcations. Starting from the reaction-diffusion equation for the heat transport, the abrupt snap-back (reset) to the insulating state is systematically formulated as a mean field Landau-like dynamics with the filament width playing the role of the order parameter. The formulation predicts an abrupt first-order phase transition with a break-off of a finite width filament across the current-controlled reset transition. The formulation is quantitatively compared against our electrical and optical microscopy experiments on VO2 thin film devices. Multi-cycle switching dynamics experiments further reveal the emergence of a stable stochastic regime following an initial electro-spatial forming phase. Beyond establishing a cross-disciplinary dynamical framework that may be readily compared to instabilities in various reaction-diffusion scenarios, the work also provides a predictive foundation for the rational design and optimization of Mott-transition-based technologies.
Comments22 Pages, 5 figures
