Symmetry of Photoexcited States and Large-Shift Raman Scattering in Two-Dimensional Mott Insulators

TL;DR

This study investigates the symmetry of photoexcited states in two-dimensional Mott insulators using exact diagonalization, revealing an s-wave symmetry for bound states and its impact on Raman scattering.

Contribution

It demonstrates that the symmetry of photoexcited bound states differs from doped cases due to fermion exchange effects, providing new insights into optical responses.

Findings

Minimum-energy bound state has s-wave symmetry.

Large-shift Raman scattering shows a minimum in the A1 channel.

Differences in symmetry explained by fermion exchange effects.

Abstract

Symmetry of photoexcited states with two photoinduced carriers in two-dimensional Mott insulators is examined by applying the numerically exact diagonalization method to finite-size clusters of a half-filled Hubbard model in the strong-coupling limit. The symmetry of minimum-energy bound state is found to be s-wave, which is different from a d_{x^2-y^2} wave of a two-hole pair in doped Mott insulators. We demonstrate that the difference is originated from an exchange of fermions due to the motion of a doubly occupied site. Correspondingly large-shift Raman scattering across the Mott gap exhibits a minimum-energy excitation in the A1 (s-wave) channel. We discuss implications of the results for the Raman scattering and other optical experiments.