Effect Of Many-body Interactions On The Ground State Of One-Dimensional Correlated Electronic System

In condensed matter physics,the one-dimensional(1D)strongly associated electron-ic system plays an important role and has been a subject of intensive research currently,motivated not only by the theoretical interest but also by the potential application prospec-t.The extended Hubbard chain is proposed to be a suitable model describing correlation effects of 1D interactive electron systems.In this thesis,we extend the Hubbard model further from two aspects.We concentrate on the case of weak coupling and half-filled band,and investigate ground-state properties of the models.Firstly,we study a 1D correlated electron system described by the t-U-J1-J2 model,focusing on the impact of frustration on the ground state of the system.By the low-energy field theory combining bosonization and renormalization-group(RG)analy-sis,we obtain the quantum phase diagram,which includes insulating spin-density-wave(SDW)and bond-order-wave(BOW)phases and a superconducting phase characterized by the coexistence of singlet superconductivity(SS)and charge-density-wave(CDW)in-stabilities.The frustration leads to the realization of the superconductivity in the case of positive interactions.Secondly,we study a 1D extended Penson-Kolb-Hubbard(PKH)model by adding a nearest-neighbor four-electron coupling.It is found that the additional four-body interaction may significantly modify the quantum phase diagram,favoring the presence of the superconducting phase even in the case of two-body repulsions.Theoretically,our study provides an important insight into the superconductivity s-cenarios,and develops the quantum theory of low-dimensional correlated systems.