Cui Xiangyue, Yan Hejin, Yan Xuefei, Zhou Kun, Cai Yongqing
Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macau, 999078, China.
School of Microelectronics Science and Technology, Sun Yat-Sen University, Zhuhai 519082, China.
ACS Nano. 2023 Sep 12;17(17):16530-16538. doi: 10.1021/acsnano.3c01229. Epub 2023 Aug 30.
As a prototype of the Weyl superconductor, layered molybdenum ditelluride (MoTe) encompasses two semimetallic phases (1T' and T) which differentiate from each other via a slight tilting of the out-of-plane lattice. Both phases are subjected to serious phase mixing, which complicates the analysis of its origin of superconductivity. Herein, we explore the electron-phonon coupling (EPC) of the monolayer semimetallic MoTe, without phase ambiguity under this thickness limit. Apart from the hardening or softening of the phonon modes, the strength of the EPC can be strongly modulated by doping. Specifically, longitudinal and out-of-plane acoustic modes are significantly activated for electron doped MoTe. This is ascribed to the presence of rich valley states and equispaced nesting bands, which are dynamically populated under charge doping. Through comparing the monolayer and bilayer MoTe, the strength of EPC is found to be less likely to depend on thickness for neutral samples but clearly promoted for thinner samples with electron doping, while for hole doping, the strength alters more significantly with the thickness than doping. Our work explains the issue of the doping sensitivity of the superconductivity in semimetallic MoTe and establishes the critical role of activating acoustic phonons in such low-dimensional materials.
作为外尔超导体的原型，层状二碲化钼（MoTe₂）包含两个半金属相（1T'和T），它们通过面外晶格的轻微倾斜而相互区分。这两个相都存在严重的相混合，这使得对其超导起源的分析变得复杂。在此，我们研究了单层半金属MoTe₂的电子 - 声子耦合（EPC），在这个厚度限制下不存在相模糊问题。除了声子模式的硬化或软化外，EPC的强度可以通过掺杂得到强烈调制。具体而言，对于电子掺杂的MoTe₂，纵向和面外声学模式被显著激活。这归因于存在丰富的谷态和等间距的嵌套能带，它们在电荷掺杂下动态填充。通过比较单层和双层MoTe₂，发现对于中性样品，EPC的强度不太可能依赖于厚度，但对于电子掺杂的较薄样品，EPC强度明显增强，而对于空穴掺杂，强度随厚度的变化比随掺杂的变化更显著。我们的工作解释了半金属MoTe₂中超导性的掺杂敏感性问题，并确立了激活声学声子在这种低维材料中的关键作用。
