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arXiv 1401.6792cond-mat.str-el
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二维$t$ - $J$模型中的高温超导:Gutzwiller波函数解

High temperature superconductivity in the two-dimensional $t$-$J$ model: Gutzwiller wave function solution

J. Kaczmarczyk, J. Bünemann, J. Spałek

摘要:

本文用最近提出的Gutzwiller波函数的系统图解展开法(DE-GWF)描述了二维正方晶格$J$模型中的超导(SC)基态,其中最近邻和次最近邻之间的跳跃电子振幅为$t$(和$t'$)。在SC状态分析的例子中,我们提供了与其他方法的方法结果的详细比较。即:(i)截断DE-GWF方法再现变分蒙特卡罗(VMC)结果;(ii)在最低(零)阶展开中,该方法可以再现标准Gutzwiller近似(GA)以及最近提出的“巨正则Gutzwiller近似”(GCGA)的分析结果。我们得到的SC状态的重要特征。首先,在费米面的SC间隙类似于一个$d_{x^2-y^2}$波,只有最佳和过掺杂的系统,被减少在负波区的欠掺杂的情况下,在定性的协议与实验。间隙结构的校正示出从真实空间配对的较长范围产生。其次,节点费米速度几乎是恒定的掺杂的函数,并同意半定量与实验结果。第三,我们比较了掺杂依赖的间隙大小与实验数据。第四,我们分析了模型的$\mathbf{k}$空间性质:费米面拓扑和有效色散。DE-GWF方法为研究强相关系统开辟了新的视角,因为:(i)它在热力学极限下工作,(ii)在精度上与VMC相当,以及(iii)具有与GA相当的数值复杂性(即,它提供的结果比VMC方法快得多)。

英文摘要:

A systematic diagrammatic expansion for Gutzwiller-wave functions (DE-GWF) proposed very recently is used for the description of superconducting (SC) ground state in the two-dimensional square-lattice $t$-$J$ model with the hopping electron amplitudes $t$ (and $t'$) between nearest (and next-nearest) neighbors. On the example of the SC state analysis we provide a detailed comparison of the method results with other approaches. Namely: (i) the truncated DE-GWF method reproduces the variational Monte Carlo (VMC) results; (ii) in the lowest (zeroth) order of the expansion the method can reproduce the analytical results of the standard Gutzwiller approximation (GA), as well as of the recently proposed "grand-canonical Gutzwiller approximation" (GCGA). We obtain important features of the SC state. First, the SC gap at the Fermi surface resembles a $d_{x^2-y^2}$-wave only for optimally- and overdoped system, being diminished in the antinodal regions for the underdoped case in a qualitative agreement with experiment. Corrections to the gap structure are shown to arise from the longer range of the real-space pairing. Second, the nodal Fermi velocity is almost constant as a function of doping and agrees semi-quantitatively with experimental results. Third, we compare the doping dependence of the gap magnitude with experimental data. Fourth, we analyze the $\mathbf{k}$-space properties of the model: Fermi surface topology and effective dispersion. The DE-GWF method opens up new perspectives for studying strongly-correlated systems, as: (i) it works in the thermodynamic limit, (ii) is comparable in accuracy to VMC, and (iii) has numerical complexity comparable to GA (i.e., it provides the results much faster than the VMC approach).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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