PhD Thesis Defense | Alvaro Ruiz Puente

Nonlinear optics from a dual perspective: from the perturbative framework to Floquet theory

November 6, 9:30

CFM Auditorium

Candidate: Alvaro Ruiz Puente

Supervisor:  Julen Ibañez Azpiroz

SUMMARY

In this thesis, we studied light–matter interactions using both perturbative (response theory) and non-perturbative (Floquet theory) approaches within the band theory framework. Using response theory, we explained the large photocurrent in TaIrTe₄ as a third-order effect and analysed the second-order injection current in multiferroic EuO—symmetry-forbidden in its rock-salt phase—as a potential mechanism for material-based filtering. In the non-perturbative regime, we applied Floquet theory to explore light–matter coupling, examining quasienergies in model systems and materials like BC₂N. We further developed a formalism for the exact time evolution of observables within this framework and demonstrated it through applications to BC₂N.

Schematic illustration of optical processes and materials studied in the thesis