Charge Transfer Model: What Is the Effect of Charge Fluctuation in t-J Model
劉弈玄1*, 李定國2
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Institute of Physics, Academia Sinica, Nankang, Taiwan
* presenting author:YiHsuan Liu,
$High−Tc $ Cuprates have been studied quite often as an effective one band $t − J$model that neglects charge fluctuation between oxygen $2p^6$ band and copper$3d^10$ band, and Zhang-Rice singlet is just a hole in the model. However, recent Scanning Tunneling Spectra(STS) measurement on underdoped Cuprate shows that charge transfer gap is only of order 1-2eV. This small gap necessitates a re-examination of the charge transfer fluctuation. Here we modify the t-J model by including charge transfer fluctuation allowing the formation of doubly occupied sites. For certain parameters it is similar with the t-J-U model. This model is studied via variational Monte Carlo method(VMC). Our result shows that this model can give a unified behavior of superconducting dome with different long rang hopping parameters. The anti-correlation between charge transfer gap and pairing is also confirmed. More interestingly the charge fluctuation is found to affect pairing order parameter in different ways in underdoped and overdoped regions.

Keywords: High T_c Cuprate, Mott Insulator, Hubbard Model, t-J model, t-J-U model