Multiphoton Resonant Excitation and High Harmonic Generation in Large Graphene Quantum Dots

We investigated the generation of higher harmonics in large graphene quantum dots under the effect of an intense laser field. Modeling a hexagonal graphene quantum dots with zigzag edges consisting of 150 atoms and its interaction with a laser field, we use the tight-binding approximation to account for the many-particle Coulomb interaction. Our detailed spectral analysis reveals the multiphoton resonant nature of the harmonic generation, shedding light on the underlying quantum processes. We examined the dependence of the cutoff harmonics on the laser intensity and frequency, providing useful insights into the optimal conditions for enhancing the generation of higher harmonics in a large graphene quantum dot. The obtained results indicated that a graphene quantum dot with 150 atoms exhibits a significant increase in high harmonic emission compared to the previously discussed graphene quantum dots.