近日，美国SLAC国家加速器实验室的Aaron M. Lindenberg&Andrey D. Poletayev及其研究团队取得一项新进展。经过不懈努力，他们利用非线性光学研究离子传导中记忆的持久性。相关研究成果已于2024年1月24日在国际权威学术期刊《自然》上发表。

该研究团队利用单周期太赫兹泵浦技术，成功地脉冲触发了电池固体电解质中的离子跳跃。这一过程通过诱导瞬态双折射实现，从而在皮秒时间尺度上直接探测离子跳跃的各向异性。瞬态信号的弛豫测量揭示了定向记忆的衰减和扩散熵的产生。研究人员进一步利用硅瞬态双折射的实验结果，确定了离子跳跃的振动尝试频率。通过非线性光学方法，他们探索了离子在最快极限下的输运特性，并在原子尺度上区分了相关的传导机制和真正的随机游走。这一研究还证明了激活输运与信息热力学之间的联系。

据悉，预测凝聚态的实际传输速率对于材料的合理设计、设备的优化以及工艺的改进至关重要，尤其在低碳能源技术的开发中，如可充电电池等领域。对于离子传导，集体机制，电导率随时间尺度和约束的变化，以及平移声子起源的模糊性，要求对离子扩散的基本步骤即离子跳跃进行直接探测。然而，由于这种跳跃是罕见的大振幅平移事件，其激发和探测极具挑战性。

附：英文原文

Title: The persistence of memory in ionic conduction probed by nonlinear optics

Author: Poletayev, Andrey D., Hoffmann, Matthias C., Dawson, James A., Teitelbaum, Samuel W., Trigo, Mariano, Islam, M. Saiful, Lindenberg, Aaron M.

Issue&Volume: 2024-01-24

Abstract: Predicting practical rates of transport in condensed phases enables the rational design of materials, devices and processes. This is especially critical to developing low-carbon energy technologies such as rechargeable batteries. For ionic conduction, the collective mechanisms, variation of conductivity with timescales and confinement, and ambiguity in the phononic origin of translation, call for a direct probe of the fundamental steps of ionic diffusion: ion hops. However, such hops are rare-event large-amplitude translations, and are challenging to excite and detect. Here we use single-cycle terahertz pumps to impulsively trigger ionic hopping in battery solid electrolytes. This is visualized by an induced transient birefringence, enabling direct probing of anisotropy in ionic hopping on the picosecond timescale. The relaxation of the transient signal measures the decay of orientational memory, and the production of entropy in diffusion. We extend experimental results using in silico transient birefringence to identify vibrational attempt frequencies for ion hopping. Using nonlinear optical methods, we probe ion transport at its fastest limit, distinguish correlated conduction mechanisms from a true random walk at the atomic scale, and demonstrate the connection between activated transport and the thermodynamics of information.

DOI: 10.1038/s41586-023-06827-6

Source: https://www.nature.com/articles/s41586-023-06827-6