Pairing Fluctuations in The Attractive Hubbard Model in the Atomic Limit

Abstract

BCS theory accounts for the pairing instability in the weak coupling limit, but fails to describe pairing fluctuations above $T_c$. One possibility for describing these fluctuations in the dilute limit is the T-matrix approximation. We critically examine various degrees of self-consistency in the T-matrix formalism, along with a non-diagrammatic two-particle self-consistent (TPSC) formulation, in the strong coupling regime, where an exact solution is readily available. We find that one particular degree of self-consistency is quite accurate, particularly at low temperature as evidenced by examining both static and dynamic properties.

5 pages, 3 figures

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• Comparative Study of BCS-BEC Crossover Theories above $T_c$: the Nature of the Pseudogap in Ultra-Cold Atomic Fermi Gases
• Two-Particle Self-Consistent method for the multi-orbital Hubbard model
• Two-Particle-Self-Consistent Approach for the Hubbard Model
• Analyzing the success of T-matrix diagrammatic theories in representing a modified Hubbard model