Doping effects in high-harmonic generation from correlated systems

Using the one-dimensional Hubbard-model, doping effects in high-harmonic generation (HHG) from correlated materials were studied. High Tc-superconducting cuprates often fall into this category of materials. The special and commonly used case of half-filling leads to Mott insulating behavior for strongly correlated materials [1-2]. For relatively small Hubbard U, i.e., small electron-electron correlation, doping had little to no effect on the dynamics nor the HHG spectra. For large U, the dynamics and spectra are heavily influenced by the degree of doping. These findings are explained through the quasiparticle-based doublon-holon picture. Doublons are doubly occupied lattice sites, and holons are unoccupied lattice sites. The dynamics are separated into two types: doublon and holon movement, and doublon-holon pair creation and annihilation. Doping results in all configurations containing doublons or holons. Those quasiparticles can move at no extra cost in energy regardless of the correlation level. This motion at no energy cost increases the high-harmonic gain for low- and medium-harmonic orders. Finally, a decrease in the probability for antiferromagnetic ordering with an increasing doping rate, in the high U limit, is discussed and used to explain a drop in the high-order harmonics relative to half-filling [3].

[1] R. E. F. Silva, I. V. Blinov, A. N. Rubtsov, O. Smirnova, and M. Ivanov,

High-harmonic spectroscopy of ultrafast many-body dynamics in strongly correlated systems,

Nature Photonics 12, 266 (2018).

[2] T. Hansen, S. V. B. Jensen, and L. B. Madsen,

Correlation effects in high-harmonic generation from finite systems,

Phys. Rev. A 105,053118 (2022)

[3] T. Hansen, and L. B. Madsen,

Doping effects in high-harmonic generation from correlated systems

Phys. Rev. B 106, 235142 (2022)