High harmonic generation in heavy fermion systems*

Since the first high harmonic generation (HHG) in crystalline solids in 2011 [1], it quickly became apparent, that the mechanism leading to HHG in solids can be used to explore the electron and lattice dynamics on ultrafast time scales. On the theoretical side the focus was initially on weakly correlated and effective single band systems. In strongly correlated systems, e.g. with localized and partially occupied orbitals, this picture can break down, as the photoinduced dynamics can induce significant changes to the electronic and structural order [2]. In this talk, we examine the nonequilibrium dynamics in a prototypical class of strongly correlated materials: heavy fermion systems. Specifically, we study laser pulse driven Kondo systems within a charge ordered regime [3] and close to criticality [4]. The HHG spectra, which can be observed in the current emission spectroscopy, strongly depend on the strength of the laser field, filling factor and the Kondo energy scale. By comparing the dynamics to time-dependent spectral functions, structure factors and local spin correlations the change of the harmonic structures are traced back to a breakdown of the Kondo insulator and a laser induced phase transition to a conductor. We propose, that HHG spectra can serve as an experimental indicator to identify the different dynamical regimes induced by the laser pulses.

[1] Ghimire, S., et al. Nature Phys 7, 138–141 (2011)
[2] Murakami, Y., et al. Phys. Rev. Lett. 121, 057405 (2018)
[3] Fauseweh, B., Zhu, J.-X., Phys. Rev. B 102, 165128 (2020)
[4] Zhu, W., et al. arXiv:1811.12334 (2018)