This work presents findings from femtosecond time-resolved spectroscopy on LaVS3, revealing interactions between carriers and phonon modes. It elucidates the effects on thermal conductivity and the emergence of metastable states due to carrier trapping within vanadium clusters.
Mott insulators are a class of strongly correlated materials with emergent properties important for modern electronics applications. The key property for application is the Electric Mott insulator to metal Transitions (EMT) whose proposed mechanism is related to the creation of hot electrons by electric field triggering an electronic avalanche after a time delay. This model suggests that the direct creation of hot carriers thanks to a laser pulse should drastically affect the EMT. We have tested this idea by performing pump-pump-probe experiments on single crystals of the Mott insulator GaTa4Se8, whereby electric and laser pulses simultaneously excite the crystal while electric probe monitors its conductivity. Our results show that the concomitant application of femtosecond laser pulse reduced the time delay of EMT by a factor up to. Measurements performed with different laser wavelengths and fluences support moreover that the EMT is driven by a hot carriers generation mechanism.
We show time resolved spectroscopy measurements with femtosecond time resolution in LaVS3 crystal. Transient reflectivity reveals the existence of a preferential coupling between the photexcited electrons and the coherently excited A1g phonon mode. The time scale of this coupling is around 140 fs, whereas the time-scale of the interaction between the A1g phonon mode and the other phonons is around 400 fs. This phonon mode is damped in less then 2 ps. On longer time scale, the transient dynamics is characterized by a long-standing plateau of reflectivity, which can be due to either low inter-plane thermal conductivity or to a metastable state caused by carrier trapping in vanadium cluster.
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