近日，德国斯图加特大学的Sebastian Loth及其研究团队取得一项新进展。经过不懈努力，他们揭示原子尺度上集体电荷密度波动力学的太赫兹光谱学。相关研究成果已于2024年7月15日在国际知名学术期刊《自然—物理学》上发表。

本文利用扫描隧道显微镜下的太赫兹泵浦探测光谱，以原子空间分辨率测量了过渡金属二硫化物2H-NbSe₂中电荷密度波的超快集体动力学。太赫兹脉冲的尖端增强电场激发电荷密度波的振荡，其振幅和频率在单个原子杂质的尺度上变化。

由表面随机分布的原子缺陷引起的重叠相激发产生了电荷密度波的空间结构响应。这种用局部探针观察集体电荷有序动力学的能力，使得在其潜在相互作用的内在长度尺度上研究相关材料的动力学成为可能。

据悉，电荷密度波是材料电子密度的波状调制，显示集体振幅和相位动力学。与原子杂质的相互作用引起电荷有序相的强空间非均质性。这种缺陷引起的电荷调制的相激励动力学没有直接的实空间观测。

附：英文原文

Title: Terahertz spectroscopy of collective charge density wave dynamics at the atomic scale

Author: Sheng, Shaoxiang, Abdo, Mohamad, Rolf-Pissarczyk, Steffen, Lichtenberg, Kurt, Baumann, Susanne, Burgess, Jacob A. J., Malavolti, Luigi, Loth, Sebastian

Issue&Volume: 2024-07-15

Abstract: Charge density waves are wave-like modulations of a material’s electron density that display collective amplitude and phase dynamics. The interaction with atomic impurities induces strong spatial heterogeneity of the charge-ordered phase. Direct real-space observation of phase excitation dynamics of such defect-induced charge modulation is absent. Here, by utilizing terahertz pump–probe spectroscopy in a scanning tunnelling microscope, we measure the ultrafast collective dynamics of the charge density wave in the transition metal dichalcogenide 2H-NbSe₂ with atomic spatial resolution. The tip-enhanced electric field of the terahertz pulses excites oscillations of the charge density wave that vary in magnitude and frequency on the scale of individual atomic impurities. Overlapping phase excitations originating from the randomly distributed atomic defects in the surface create this spatially structured response of the charge density wave. This ability to observe collective charge order dynamics with local probes makes it possible to study the dynamics of correlated materials at the intrinsic length scale of their underlying interactions.

DOI: 10.1038/s41567-024-02552-7

Source: https://www.nature.com/articles/s41567-024-02552-7