Optical creation and temperature stability of the hidden charge density wave state in 1T-TaS_{2-x}Se_{x}

Abstract

The femtosecond transinet optical spectroscopy is employed to study the relaxation dynamics of the equilibrium and hidden metastable charge-density-wave states in single crystals of 1$T$-TaS$_{2-x}$Se$_{x}$ as a function of the Se doping $x$. Similarly to pristine 1$T$-TaS$_{2}$, the transition to a hidden phase is observed at low temperature after a quench with a single 50~fs laser pulse, in the commensurate Mott phase up to $x=0.6$. The photo-induced hidden-phase formation is accompanied by a notable change in the coherent phonon spectra, and particularly the collective amplitude mode. While the stability of the hidden phase with increased temperatures is only slightly dependent of the Se content the hidden-phase creation-treshold fluence strongly increases with the Se content from 1 to $\sim4$ mJ/cm$^{2}$.