de Quesada Felipe A, Muscher Philipp K, Krakovsky Eliana S, Sood Aditya, Poletayev Andrey D, Sie Edbert J, Nyby Clara M, Irvine Sara J, Zajac Marc E, Luo Duan, Shen Xiaozhe, Hoffmann Matthias C, Kramer Patrick L, England R Joel, Reid Alexander H, Weathersby Stephen P, Dresselhaus-Marais Leora E, Rehn Daniel A, Chueh William C, Lindenberg Aaron M
Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA.
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
Adv Sci (Weinh). 2025 Feb;12(6):e2411344. doi: 10.1002/advs.202411344. Epub 2024 Dec 16.
The unique layer-stacking in two-dimensional (2D) van der Waals materials facilitates the formation of nearly degenerate phases of matter and opens novel routes for the design of low-power, reconfigurable functional materials. Electrochemical ion intercalation between stacked layers offers a promising approach to stabilize bulk metastable phases and to explore the effects of extreme carrier doping and strain. However, in situ characterization methods to study the structural evolution and dynamical functional properties of these intercalated materials remains limited. Here a novel experimental platform is presented capable of simultaneously performing electrochemical lithium-ion intercalation and multimodal ultrafast characterization of the lattice using both electron diffraction and nonlinear optical techniques. Using the layered semimetal WTe as a model system, the interlayer shear phonon mode that modulates stacking between 2Dlayers is probed, showing that small amounts of lithiation enhance the amplitude and lifetime of the phonon, contrary to expectations. This results from the dynamically fluctuating and anharmonic structure between nearly degenerate phases at room temperature, which can be stabilized by electronic carriers accompanying the inserted lithium ions. At high lithiation, the T' structure emerges and quenches the phonon response. This work defines new approaches for using electrochemistry to engineer the dynamic structure of 2D materials.
二维范德华材料中独特的层状堆叠有助于形成近简并的物相，并为低功耗、可重构功能材料的设计开辟了新途径。堆叠层之间的电化学离子插层为稳定体相亚稳相以及探索极端载流子掺杂和应变的影响提供了一种很有前景的方法。然而，用于研究这些插层材料的结构演变和动态功能特性的原位表征方法仍然有限。本文介绍了一种新型实验平台，该平台能够同时进行电化学锂离子插层，并使用电子衍射和非线性光学技术对晶格进行多模态超快表征。以层状半金属WTe₂作为模型体系，探测了调制二维层间堆叠的层间剪切声子模式，结果表明，与预期相反，少量锂化会增强声子的振幅和寿命。这是由于室温下近简并相之间动态波动且非谐的结构，伴随插入锂离子的电子载流子可以使其稳定。在高锂化时，T'结构出现并淬灭声子响应。这项工作为利用电化学手段调控二维材料的动态结构定义了新方法。
