Light absorption spectrum of two-dimensional Mott insulators

摘要: We theoretically investigate the light absorption spectrum of two-dimensional (2D) Mott insulators. employ numerical diagonalization method to calculate with using effective Hamiltonian for extended Hubbard model, which is valid when on-site Coulomb interaction energy $U$ much larger than nearest-neighbor transfer integral $t$ and $V$. For $V=0$, consists a broad band width about $16t$ sharp central peak, eigenstates contributing do not have antiferromagnetic (AF) spin order, sufficiently $t$. These features result from spin-charge interplay inherent in very strong correlation region where charge term dominant. With decreasing $U∕t$, peak structure becomes unclear some low AF as spin-spin term. large $V∕t$, dominant arises lower spectrum. A number holon-doublon bound states, nearly same but different structures, are responsible this contrast conventional exciton state. This also states one-dimensional (1D) insulators, single eigenstate dominates optical transition moment separation. The essentially spectra between 1D 2D insulators originate difference coupling degrees freedom.