Department of Communication Engineering, Oriental Institute of Technology, Banqiao Area, New Taipei City 22061, Taiwan.
J Phys Condens Matter. 2011 Dec 14;23(49):495602. doi: 10.1088/0953-8984/23/49/495602. Epub 2011 Nov 18.
Extended t-t'-t"-J-U models in which the second-nearest-neighbor hopping (t') and third-nearest-neighbor hopping (t") are included are studied using renormalized mean field theory. The models are meant to be low-energy effective models for the Hubbard models, and hence the Heisenberg exchange integral J and Hubbard repulsion U are related by J = 4t(2)/U. The trial wavefunctions for the ground states are partially Gutzwiller projected Hartree-Fock states. The Gutzwiller projection is implemented by means of a Gutzwiller approximation, and the site double occupancy d is taken as a variational parameter. It is found that a large |t'/t| narrows the band filling range that sustains antiferromagnetism (AFM) in the ground state, enhances the d-wave singlet superconductivity (dSC) in hole overdoped systems, but suppresses the dSC in electron overdoped systems. For a system that has large |t'/t| and |t"/t'|, the superconductivity (SC) at the onset of AFM in hole doped band filling is strongly suppressed. On the excitation occurring, when an electron doped system simultaneously contains SC and AFM, the system is found to have a nodeless gap at the Fermi level. Finally, the result of this study is related to experiments on the superconducting cuprates.
采用重整化平均场理论研究了包含第二近邻跳跃（t'）和第三近邻跳跃（t"）的扩展 t-t'-t"-J-U 模型。这些模型是 Hubbard 模型的低能有效模型，因此，Heisenberg 交换积分 J 和 Hubbard 排斥 U 由 J = 4t(2)/U 相关。基态的试探波函数是部分 Gutzwiller 投影哈特ree-Fock 态。Gutzwiller 投影通过 Gutzwiller 近似来实现，并且将位双占据 d 作为变分参数。研究发现，较大的 |t'/t| 会缩小在基态中维持反铁磁（AFM）的能带填充范围，增强了过掺杂空穴系统中的 d 波单态超导性（dSC），但抑制了过掺杂电子系统中的 dSC。对于具有较大 |t'/t| 和 |t"/t'| 的系统，在空穴掺杂带填充中 AFM 起始时的超导性（SC）被强烈抑制。在激发发生时，当电子掺杂系统同时包含 SC 和 AFM 时，系统在费米能级处被发现具有无节点间隙。最后，这项研究的结果与超导 cuprates 的实验有关。
