文档介绍：Abstract
Wi也iIl the t-J-U mode and Gutzwiller mean-field approximation,the ground state
phase diagram and the influence of the additional second-neighbor hopping t on the
phase diagram of the copper oxide materials are studied systemically.
们舱paper anized as Chapter I,a brief review of the development of cuprate material is we introduce the t-J-U model which is able to describe the essential low—energy physics of cuprates and the Gutzwiller mean-field approximation which Can treat the strong correlation between the electrons properly.
Within the t-J—U mode and Gutzwiller mean—field approximation,the phase diagrams of gossamer superconductors are studied in Chapter II:firstly,we study the d—wave superconductivity(dSC)and ism(AF)in a renormalized mean field theory.
弧e phase diagrams as functions of doping 6 and U are the standard value
of tZJ= and in the large U limit,we find mat the AF order emerges and coexists with the
dSC in the underdoped region below the doping dSC order parameter increases from zero as the doping increases and reaches a maximum near the optimal doping 5. In the small U limit,only the dSC order survives while the AF order U increases up to a critical value,the AF order shows up and coexists with the dSC in the underdoped half filling,the system is in the dSC state for small U and es an AF insulator for large U
Finally we study the influence of the additional second-neighbor hopping t’on the phase diagram in Chapter find that for the small values of f,,the qualitative feature of the ground state phase diagram in the t-t'-J-U model is the same as in the case of
the t-JjU model,where the AF order coexists wim the dSC in the underdoped region, while the dSC order parameter is slightly suppressed in the underdoped regions,and greatly enhanced in the optimal and overdoped regions with the increasing of the f,.As a result,the coexistence region of the AF and dSC