Coelho Paula Mariel, Lasek Kinga, Nguyen Cong Kien, Li Jingfeng, Niu Wei, Liu Wenqing, Oleynik Ivan I, Batzill Matthias
Department of Physics, University of South Florida, Tampa, Florida 33620, United States.
Department of Electronic Engineering, Royal Holloway University of London, Egham TW20 0EX, U.K.
J Phys Chem Lett. 2019 Sep 5;10(17):4987-4993. doi: 10.1021/acs.jpclett.9b01949. Epub 2019 Aug 15.
Interlayer interactions in layered transition metal dichalcogenides are known to be important for describing their electronic properties. Here, we demonstrate that the absence of interlayer coupling in monolayer VTe also causes their structural modification from a distorted 1T' structure in bulk and multilayer samples to a hexagonal 1T structure in the monolayer. X-ray photoemission spectroscopy indicates that this structural transition is associated with electron transfer from the vanadium d bands to the tellurium atoms for the monolayer. This charge transfer may reduce the in-plane d orbital hybridization and thus favor the undistorted 1T structure. Phonon-dispersion calculations show that, in contrast to the 1T' structure, the 1T structure exhibits imaginary phonon modes that lead to a charge density wave (CDW) instability, which is also observed by low-temperature scanning tunneling microscopy as a 4 × 4 periodic lattice distortion. Thus, this work demonstrates a novel CDW material, whose properties are tuned by interlayer interactions.
层状过渡金属二硫属化物中的层间相互作用对于描述其电子性质很重要。在此，我们证明单层VTe中层间耦合的缺失也导致其结构从体相和多层样品中的扭曲1T'结构转变为单层中的六方1T结构。X射线光电子能谱表明，这种结构转变与单层中从钒d带向碲原子的电子转移有关。这种电荷转移可能会减少面内d轨道杂化，从而有利于未扭曲的1T结构。声子色散计算表明，与1T'结构不同，1T结构表现出虚声子模式，导致电荷密度波（CDW）不稳定性，低温扫描隧道显微镜也观察到这一点，表现为4×4周期性晶格畸变。因此，这项工作展示了一种新型的CDW材料，其性质由层间相互作用调节。
