The low characteristic energy scale inherent in heavy fermion systems makes them a natural platform for ultra-short laser pulses to optically modulate the electronic properties of these intricate quantum materials. In this study, we investigated the quasiparticle dynamics in heavy fermion CeCoGe₃ using in-situ high-pressure femtosecond optical pump-probe spectroscopy. For the first time, we successfully observed the opening of the Kondo gap in heavy fermion CeCoGe₃ at ambient temperature and high pressure (35 GPa, P^*). Additionally, before the establishment of heavy electron coherence, this material system exhibited hybridization fluctuations (23 GPa, P^#). Following the establishment of heavy electron coherence, we promptly discerned an additional negative relaxation channel associated with the Kondo screening effect. As the pump fluence increases, this negative relaxation channel is attenuated, indicating that under high fluence, the hybridization between the conduction band and the 4f band is partially reversed, thereby reducing the gap. Finally, we revealed that the phonon frequency dependence observed beyond the pressure point denoted as P^# is directly linked to the manifestation of hybridization fluctuations. These findings offer pivotal insights into understanding the hybridization dynamics in heavy fermion systems under high pressure.
 

heavy fermion,high pressure,pump probe,ultrafast laser