Effect of Impurity on the Doping-Induced in-Gap States in a Mott Insulator

Abstract

Motivated by the recent measurements of the spatial distribution of single particle excitation states in a hole-doped Mott insulator, we study the effects of impurity on the in-gap states, induced by the doped holes, in the Hubbard model on the square lattice by the cluster perturbation theory. We find that a repulsive impurity potential can move the in-gap state from the lower Hubbard band towards the upper Hubbard band, providing a good account for the experimental observation. The distribution of the spectral function in the momentum space can be used to discriminate the in-gap state induced by doped holes and that by the impurity. The spatial characters of the in-gap states in the presence of two impurities are also discussed and compared to the experiment.

Mott Gap Filling by Doping Electrons through Depositing One Sub-Monolayer Thin Film of Rb on Ca2CuO2Cl2

“…Based on the theoretical calculation, hole doping may induce the in-gap state near the CTB, [13] and the in-gap state may move to the UHB due to a repulsive impurity potential. [34] Meanwhile, electron doping can also induce an in-gap state below the UHB. [35] However, we would argue that the location of the local DOS peak induced by the Ca or Cl vacancies seems to be an effect strongly linked with the edge of the UHB, but not the repulsive impurity potential effect, since their locations and features look quite similar, despite the impurities of Cl and Ca vacancies are very different.…”

“…[46] We note that there is a theoretical calculation concerning repulsive impurity potential that try to explain this unconventional in-gap state. [34] However, to unravel the origin of the Ca vacancy induced in-gap state may require further theoretical studies.…”