Abstract
We establish time-resolved high harmonic generation (tr-HHG) as a powerful spectroscopy for photoinduced dynamics in strongly correlated materials through a detailed investigation of the insulator-to-metal transitions in vanadium dioxide. We benchmark our technique by comparing our measurements to established momentum-resolved ultrafast electron diffraction, and theoretical density functional calculations. Tr-HHG allows distinguishing of individual dynamic channels, including a transition to a thermodynamically hidden phase. In addition, the HHG yield is shown to be modulated at a frequency characteristic of a coherent phonon in the equilibrium monoclinic phase over a wide range of excitation fluences. These results demonstrate that tr-HHG is capable of tracking complex dynamics in solids through its sensitivity to the band structure.
Highlights
As ultrashort light and electron sources have become more advanced, real-time dynamics of complex states of matter may be understood in greater detail [1,2]
We have demonstrated time-resolved high harmonic generation (tr-High-harmonic generation (HHG)) spectroscopy from a strongly correlated material
We have shown that tr-HHG is capable of discriminating and tracking the real-time evolution of the distinct phase transitions and associated coherent phonon dynamics in VO2, including observations of the hidden metastable M phase that has no equilibrium analog
Summary
As ultrashort light and electron sources have become more advanced, real-time dynamics of complex states of matter may be understood in greater detail [1,2]. High-harmonic generation (HHG) in atoms and molecules is a well-known process for generating table-top ultrafast sources from the extreme ultraviolet (EUV) to the soft x-ray spectral range, and has been used for probing dynamics in matter [1,3,4,5]. High-harmonic spectroscopy [3] has had great success probing electronic structure and dynamics in atoms, molecules [5,6,7,8], as well as in following chemical reactions in the gas phase [9,10,11]. Extending the generation of high-harmonics to solid state systems [12,13,14] allows for highly sensitive probing of the band structure of the generating material [15,16,17,18,19].
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