Ultrafast melting of charge-density wave fluctuations at room temperature in $1T-TiS{e}_2$ monitored under non-equilibrium conditions

Abstract

We investigate the ultrafast lattice dynamics in $1T-TiS{e}_2$ using femtosecond reflection pump-probe and pump-pump-probe techniques at room temperature. The time-domain signals and Fourier-transformed spectra show the $A_{1g}$ phonon mode at 5.9 THz. Moreover, we observe an additional mode at $\approx$ 3 THz, corresponding to the charge-density wave (CDW) amplitude mode, which is generally visible below T${}_c\approx 200$K. We argue that the emergence of the CDW amplitude mode at room temperature can be a consequence of fluctuations of order parameters, based on the additional experiment using the pump-pump-probe technique, which exhibited suppression of the AM signal within the ultrafast time scale of $\sim$ 0.5 ps.

15 pages, 3 figures, Applied Physics Letters, in press

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