Ji Yanda, Cheng Lei, Li Ning, Yuan Ye, Liang Weizheng, Yang Hao
Department of Applied Physics, College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 211106, People's Republic of China.
School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan, 610031, People's Republic of China.
J Phys Condens Matter. 2021 Mar 10;33(10):105603. doi: 10.1088/1361-648X/abd117.
The coupling between the metal-insulator transition (MIT) and the structural phase transition (SPT) in VO has been at the center of discussion for several decades, while the underlying mechanisms of electron-lattice or electron-electron interactions remain an open question. Until recently, the equilibrium state VO is believed to be a non-standard Mott-Hubbard system, i.e., both of the two interactions cooperatively work on MIT, indicating the association between MIT and SPT. However, due to the pronounced contribution of strain in strongly correlated systems, it is desirable to explore the correspondence in an interface-engineered VO. Herein, we investigate the carrier dynamics in the VO films with anomalous MIT on the basis of time-resolved transient differential reflectivity measurements. Unexpectedly, MIT is decoupled from SPT, in sharp contrast with the case of strain-free VO films: MIT is triggered by bandgap recombination below 75 °C during heating, while intense SPT-induced signal appears separately between 70 °C and 100 °C. The decoupling between MIT and SPT provides insights into the interfacial interactions in VO thin films.
几十年来，VO中金属-绝缘体转变（MIT）与结构相变（SPT）之间的耦合一直是讨论的焦点，而电子-晶格或电子-电子相互作用的潜在机制仍然是一个悬而未决的问题。直到最近，平衡态VO被认为是一个非标准的莫特-哈伯德体系，即这两种相互作用在MIT中协同起作用，这表明了MIT与SPT之间的关联。然而，由于应变在强关联体系中的显著贡献，探索界面工程VO中的对应关系是很有必要的。在此，我们基于时间分辨瞬态差分反射率测量，研究了具有反常MIT的VO薄膜中的载流子动力学。出乎意料的是，MIT与SPT解耦，这与无应变VO薄膜的情况形成鲜明对比：加热过程中低于75°C时，MIT由带隙复合触发，而强烈的SPT诱导信号则在70°C至100°C之间单独出现。MIT与SPT之间的解耦为VO薄膜中的界面相互作用提供了见解。
