Photoinduced Band Renormalization Effects in ZrSiS Topological Nodal-line Semimetal

Out-of-equilibrium effects provide an elegant pathway to probing and understanding the underlying physics of topological materials. Creating exotic states of matter using ultrafast optical pulses in particular has shown promise towards controlling electronic band structure properties. Of recent interest is band renormalization in Dirac and Weyl semimetals as it leads to direct physical observables through the enhancement of the effective mass, or, in the shift of resonant energies. Here we provide experimental and theoretical signatures of photo-induced renormalization of the electronic band structure in a topological nodal line semimetal ZrSiS. Specifically, we show how the change of the transient reflectivity spectra under femtosecond optical excitations is induced by out-of-equilibrium effects that renormalize the kinetic energy of electrons. We associate the observed spectral shift to an enhancement of the effective mass and to a red-shift of the resonant frequency as a function of pump field strength. Finally, we show that the transient relaxation dynamics of the reflectivity is primarily an electronic effect with negligible phononic contribution. Our study presents the modifications of electronic properties in ZrSiS using ultrashort pulses, and demonstrates the potential of this approach in creating photo-induced phases in topological quantum mater through an all-optical route.