Resonant Two-Magnon Raman Scattering and Photoexcited States in Two-Dimensional Mott Insulators

TL;DR

This study explores how resonant two-magnon Raman scattering in 2D Mott insulators is enhanced at photon energies above the optical absorption edge, revealing a new resonance mechanism linked to charge excitations.

Contribution

It demonstrates a novel resonance mechanism in 2D Mott insulators, differing from previous theories, using numerical diagonalization of the Hubbard model.

Findings

Raman intensity peaks at photon energies above the absorption edge.

Absence of resonance near the gap edge due to background spins.

Resonant states are characterized by charge degrees of freedom.

Abstract

We investigate the resonant two-magnon Raman scattering in two-dimensional (2D) Mott insulators by using a half-filled 2D Hubbard model in the strong coupling limit. By performing numerical diagonalization calculations for small clusters, we find that the Raman intensity is enhanced when the incoming photon energy is not near the optical absorption edge but well above it, being consistent with experimental data. The absence of resonance near the gap edge is associated with the presence of background spins, while photoexcited states for resonance are found to be characterized by the charge degree of freedom. The resonance mechanism is different from those proposed previously.