Decoupled few-femtosecond phase transitions in vanadium dioxide
arxiv(2024)
摘要
The nature of the insulator-to-metal phase transition in vanadium dioxide
(VO2) is one of the longest-standing problems in condensed-matter physics.
Ultrafast spectroscopy has long promised to determine whether the transition is
primarily driven by the electronic or structural degree of freedom, but
measurements to date have been stymied by their sensitivity to only one of
these components and/or their limited temporal resolution. Here we use
ultra-broadband few-femtosecond pump-probe spectroscopy to resolve the
electronic and structural phase transitions in VO2 at their fundamental time
scales. We find that the system transforms into a bad-metallic phase within 10
fs after photoexcitation, but requires another 100 fs to complete the
transition, during which we observe electronic oscillations and a partial
re-opening of the bandgap, signalling a transient semi-metallic state.
Comparisons with tensor-network simulations and density-functional theory
calculations show these features originate from oscillations around the
equilibrium high-symmetry atomic positions during an unprecedentedly fast
structural transition, in which the vanadium dimers separate and untwist with
two different timescales. Our results resolve the complete structural and
electronic nature of the light-induced phase transition in VO2 and establish
ultra-broadband few-femtosecond spectroscopy as a powerful new tool for
studying quantum materials out of equilibrium.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要