Theoretical Study of Optical Properties in Mott Insulating Cuprates

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Charge gap in the Mott insulator originates from strong electron correlation. Therefore, we expect optical responses that are different from those in the band insulator. In this project, we theoretically examine photoexcitaed states and optical properties in insulating copper oxides that are typical Mott insulators by using a half-filled Hubbard model and its effective model. We use the numerically exact diagonalization technique and the dynamical version of density-matrix renormalization method to calculate optical responses of the models.We obtained several new results that are related to issue of 1)excitonic effects on the optical response in the one-dimensional two-band Hubbard model at half filling, 2)theoretical prediction of angle-resolved two-photon photoemission in two-dimensional insulating cuprates in order to clarify unoccupied states above the Fermi level, 3)temperature dependence of spinon and holon excitations seen in the single-particle spectral function of one-dimensional Mott insulators, 4)the symmetry of magnetic exciton in the photoexcited states of two-dimensional Mott insulators, and 5)the effect of electron-phonon interaction on the single-particle spectral function of one-dimensional Mott insulators. We note that The topics from 1) to 4) have been summarized and published in journals like the Physical Review B, and the topic 5) is submitted to a journal.