Diego Josu, Said A H, Mahatha S K, Bianco Raffaello, Monacelli Lorenzo, Calandra Matteo, Mauri Francesco, Rossnagel K, Errea Ion, Blanco-Canosa S
Centro de Física de Materiales (CSIC-UPV/EHU), 20018, San Sebastián, Spain.
Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA.
Nat Commun. 2021 Jan 26;12(1):598. doi: 10.1038/s41467-020-20829-2.
Understanding of charge-density wave (CDW) phases is a main challenge in condensed matter due to their presence in high-Tc superconductors or transition metal dichalcogenides (TMDs). Among TMDs, the origin of the CDW in VSe remains highly debated. Here, by means of inelastic x-ray scattering and first-principles calculations, we show that the CDW transition is driven by the collapse at 110 K of an acoustic mode at q = (2.25 0 0.7) r.l.u. The softening starts below 225 K and expands over a wide region of the Brillouin zone, identifying the electron-phonon interaction as the driving force of the CDW. This is supported by our calculations that determine a large momentum-dependence of the electron-phonon matrix-elements that peak at the CDW wave vector. Our first-principles anharmonic calculations reproduce the temperature dependence of the soft mode and the T onset only when considering the out-of-plane van der Waals interactions, which reveal crucial for the melting of the CDW phase.
由于电荷密度波（CDW）相存在于高温超导体或过渡金属二硫属化物（TMD）中，因此对其理解是凝聚态物质领域的一个主要挑战。在TMD中，VSe中CDW的起源一直存在激烈争论。在这里，通过非弹性X射线散射和第一性原理计算，我们表明CDW转变是由q = (2.25 0 0.7) r.l.u.处的声学模式在110 K时的崩塌驱动的。软化在225 K以下开始，并在布里渊区的广泛区域扩展，这表明电子 - 声子相互作用是CDW的驱动力。这得到了我们计算结果的支持，这些计算确定了电子 - 声子矩阵元具有很大的动量依赖性，且在CDW波矢处达到峰值。我们的第一性原理非谐性计算仅在考虑面外范德华相互作用时，才重现了软模的温度依赖性和转变温度，这表明面外范德华相互作用对于CDW相的熔化至关重要。
