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arXiv 1402.4329cond-mat.str-el
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具有连续动量依赖的动态团簇近似中的两粒子关联:二维哈伯德模型中的超导性

Two-particle correlations in a dynamic cluster approximation with continuous momentum dependence: Superconductivity in the 2D Hubbard model

Peter Staar, Thomas Maier, Thomas Schulthess

摘要:

最近引入的DCA $^+$算法扩展的动态集团近似(DCA)与连续的晶格自能,以实现更好的收敛与集团大小。在这里,我们通过引入与DCA $^+$自能一致的具有连续动量依赖性的不可约顶点函数,将DCA $^+$算法扩展到两粒子关联函数的计算。这使得相变的研究比DCA更可控和可靠。我们通过计算有吸引力的哈伯德模型中的超导转变温度$T_{c}$来测试新方法,并表明它再现了以前的高精度确定性量子Monte Carlo结果。然后,我们计算$T_c$在掺杂排斥哈伯德模型,以前的DCA计算只能访问弱耦合($U=4t$)制度的大型集群。我们发现,新算法提供了访问更大的集群,并提供渐近收敛的结果$T_c$弱($U=4t$)和中间($U=7t$)耦合制度,从而使精确的无限集群大小的结果的准确测定。

英文摘要:

The DCA$^+$ algortihm was recently introduced to extend the dynamic cluster approximation (DCA) with a continuous lattice self-energy in order to achieve better convergence with cluster size. Here we extend the DCA$^+$ algorithm to the calculation of two-particle correlation functions by introducing irreducible vertex functions with continuous momentum dependence consistent with the DCA$^+$ self-energy. This enables a significantly more controlled and reliable study of phase transitions than with the DCA. We test the new method by calculating the superconducting transition temperature $T_{c}$ in the attractive Hubbard model and show that it reproduces previous high-precision determinantal quantum Monte Carlo results. We then calculate $T_c$ in the doped repulsive Hubbard model, for which previous DCA calculations could only access the weak-coupling ($U=4t$) regime for large clusters. We show that the new algorithm provides access to much larger clusters and delivers asymptotically converged results for $T_c$ for both the weak ($U=4t$) and intermediate ($U=7t$) coupling regimes, and thereby enables the accurate determination of the exact infinite cluster size result.

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