# Inhibition of the photoinduced structural phase transition in the excitonic insulator ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$

• Mor, Selene Department of Physical Chemistry, Fritz-Haber-Institut der MPG, Berlin, Germany
• Herzog, Marc Department of Physical Chemistry, Fritz-Haber-Institut der MPG, Berlin, Germany - Institute for Physics and Astronomy, University of Potsdam, Germany
• Noack, Johannes Department of Inorganic Chemistry, Fritz-Haber-Institut der MPG, Berlin, Germany
26.03.2018
Published in:
• Physical Review B. - 2018, vol. 97, no. 11, p. 115154
English Femtosecond time-resolved midinfrared reflectivity is used to investigate the electron and phonon dynamics occurring at the direct band gap of the excitonic insulator Ta2NiSe5 below the critical temperature of its structural phase transition. We find that the phonon dynamics show a strong coupling to the excitation of free carriers at the Γ point of the Brillouin zone. The optical response saturates at a critical excitation fluence FC=0.30±0.08 mJ/cm2 due to optical absorption saturation. This limits the optical excitation density in Ta2NiSe5 so that the system cannot be pumped sufficiently strongly to undergo the structural change to the high-temperature phase. We thereby demonstrate that Ta2NiSe5 exhibits a blocking mechanism when pumped in the near-infrared regime, preventing a nonthermal structural phase transition.
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
• English
Classification
Physics