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First-Order Pairing Transition and Single-Particle Spectral Function in the Attractive Hubbard Model

M. Capone·C. Castellani·M. Grilli
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Abstract

A Dynamical Mean Field Theory analysis of the attractive Hubbard model is carried out. We focus on the normal state upon restricting to solutions where superconducting order is not allowed. Nevertheless a clear first-order pairing transition as a function of the coupling takes place at all the electron densities out of half-filling. The transition occurs between a Fermi liquid, stable for $U < U_c$, and an insulating bound pairs phase for $U > U_c$. The spectral function in the Fermi liquid phase is constituted by a low energy structure around the Fermi level (similar to the Kondo resonance of the repulsive half-filled model), which disappears discontinuously at $U=U_c$, and two high energy features (lower and upper Hubbard bands), which persist in the insulating phase.

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M. Capone, C. Castellani, M. Grilli. 2002-02-21. First-Order Pairing Transition and Single-Particle Spectral Function in the Attractive Hubbard Model. https://doi.org/10.1103/physrevlett.88.126403

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