Temperature and dimensionality dependencies of optical absorption spectra in Mott insulators

Hidekatsu Suzuura, Akira Furusaki, Naoto Nagaosa

禎通 前川

H. Onodera, Takami Tohyama, Sadamichi Maekawa

We investigate the temperature dependence of optical absorption spectra of one-dimensional (1D) and two-dimensional (2D) Mott insulators by using an effective model in the strong-coupling limit of a half-filled Hubbard model. In the numerically exact diagonalization calculations on finite-size clusters, we find that in 1D the energy position of the absorption edge is almost independent of temperature, while in 2D the edge position shifts to lower energy with increasing temperature. The different temperature dependence between 1D and 2D is attributed to the difference of the coupling of the charge and spin degrees of freedom. The implications of the results on experiments are discussed in terms of the dimensionality dependence.

Takanobu Jujo

We investigate the two-photon absorption (TPA) spectrum in Mott insulators on the basis of dynamical cluster approximation. The nonlocal correlation is found to be important in enhancing the dimensionality dependence of the TPA spectrum. The dependence of the TPA spectrum on Coulomb interaction is modified compared with that of the dynamical mean field theory, which is also caused by a nonlocal correlation through a one-particle spectrum. We compare several degrees of nonlocality by adjusting the cluster momentum. The iterated perturbation theory is adopted as an impurity solver, and then a comparison with the noncrossing approximation is presented. It is confirmed that the predominant optical process in Mott insulators is different from that of conventional semiconductors, and small Mott insulating gaps are favorable for obtaining a large TPA spectrum.

Makoto Takahashi, Takami Tohyama, Sadamichi Maekawa

M. Takahashi, Takami Tohyama, Sadamichi Maekawa