Salev Pavel, Kisiel Elliot, Sasaki Dayne, Gunn Brandon, He Wei, Feng Mingzhen, Li Junjie, Tamura Nobumichi, Poudyal Ishwor, Islam Zahirul, Takamura Yayoi, Frano Alex, Schuller Ivan K
Department of Physics and Astronomy, University of Denver, Denver, CO 80210.
Department of Physics, University of California San Diego, La Jolla, CA 92093.
Proc Natl Acad Sci U S A. 2024 Aug 20;121(34):e2317944121. doi: 10.1073/pnas.2317944121. Epub 2024 Aug 15.
Electrical triggering of a metal-insulator transition (MIT) often results in the formation of characteristic spatial patterns such as a metallic filament percolating through an insulating matrix or an insulating barrier splitting a conducting matrix. When MIT triggering is driven by electrothermal effects, the temperature of the filament or barrier can be substantially higher than the rest of the material. Using X-ray microdiffraction and dark-field X-ray microscopy, we show that electrothermal MIT triggering leads to the development of an inhomogeneous strain profile across the switching device, even when the material does not undergo a pronounced, discontinuous structural transition coinciding with the MIT. Diffraction measurements further reveal evidence of unique features associated with MIT triggering including lattice distortions, tilting, and twinning, which indicate structural nonuniformity of both low- and high-resistance regions inside the switching device. Such lattice deformations do not occur under equilibrium, zero-voltage conditions, highlighting the qualitative difference between states achieved through increasing temperature and applying voltage in nonlinear electrothermal materials. Electrically induced strain, lattice distortions, and twinning could have important contributions in the MIT triggering process and drive the material into nonequilibrium states, providing an unconventional pathway to explore the phase space in strongly correlated electronic systems.
金属-绝缘体转变（MIT）的电触发通常会导致形成特征性的空间图案，例如金属细丝渗透过绝缘基质或绝缘势垒分割导电基质。当MIT触发由电热效应驱动时，细丝或势垒的温度可能会比材料的其余部分高得多。利用X射线微衍射和暗场X射线显微镜，我们表明，即使材料在与MIT同时发生明显的、不连续的结构转变，电热MIT触发也会导致开关器件上出现不均匀的应变分布。衍射测量进一步揭示了与MIT触发相关的独特特征的证据，包括晶格畸变、倾斜和孪晶，这表明开关器件内低电阻和高电阻区域的结构不均匀性。这种晶格变形在平衡零电压条件下不会发生，突出了通过升高温度和在非线性电热材料中施加电压所达到的状态之间的质的差异。电致应变、晶格畸变和孪晶可能在MIT触发过程中起重要作用，并将材料驱动到非平衡状态，为探索强关联电子系统中的相空间提供了一条非常规途径。
