Photoinduced Fano resonance of coherent phonons in zinc

Utilizing femtosecond optical pump-probe technique, we have studied transient Fano resonance in zinc. At high excitation levels the Fourier spectrum of the coherent E2g phonon exhibits strongly asymmetric line shape, which is well modeled by the Fano function. The Fano parameter (1∕Q) was found to be strongly excitation fluence dependent while depending weakly on the initial lattice temperature. We attribute the origin of the Fano resonance to the coupling of a coherent phonon to the electronic continuum, with their transition probabilities strongly renormalized in the vicinity of the photoinduced structural transition