The coupling between the metal-insulator transition (MIT) and the structural phase transition (SPT) in VO2has 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 VO2is 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 VO2. Herein, we investigate the carrier dynamics in highly strained VO2films 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 VO2films: MIT is triggered by bandgap recombination below 75oC during heating, while intense SPT-induced signal appears separately between 70oC and 100oC. The decoupling between MIT and SPT provides insights into the interfacial interactions in VO2thin films.

中文翻译：

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界面工程VO2中金属-绝缘体转变和结构相变之间的去耦

几十年来，VO2 中金属-绝缘体转变 (MIT) 和结构相变 (SPT) 之间的耦合一直是讨论的中心，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 VO2 被认为是一个非标准的 Mott-Hubbard 系统，即两种相互作用在 MIT 上协同工作，表明 MIT 和 SPT 之间的关联。然而，由于应变在强相关系统中的显着贡献，因此需要探索界面工程 VO2 中的对应关系。在此，我们基于时间分辨瞬态差分反射率测量研究了具有异常 MIT 的高应变 VO2 薄膜中的载流子动力学。没想到 MIT 和 SPT 解耦了，与无应变 VO2 薄膜的情况形成鲜明对比：MIT 在加热过程中由低于 75oC 的带隙复合触发，而在 70oC 和 100oC 之间分别出现强烈的 SPT 诱导信号。MIT 和 SPT 之间的解耦提供了对 VO2 薄膜中界面相互作用的见解。