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Potential-energy (BCS) to kinetic-energy (BEC)-driven pairing in the attractive Hubbard model

B. Kyung·A. Georges·A. -M. S. Tremblay
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Abstract

The BCS-BEC crossover within the two-dimensional attractive Hubbard model is studied by using the Cellular Dynamical Mean-Field Theory both in the normal and superconducting ground states. Short-range spatial correlations incorporated in this theory remove the normal-state quasiparticle peak and the first-order transition found in the Dynamical Mean-Field Theory, rendering the normal state crossover smooth. For $U$ smaller than the bandwidth, pairing is driven by the potential energy, while in the opposite case it is driven by the kinetic energy, resembling a recent optical conductivity experiment in cuprates. Phase coherence leads to the appearance of a collective Bogoliubov mode in the density-density correlation function and to the sharpening of the spectral function.

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B. Kyung, A. Georges, A. -M. S. Tremblay. 2006-07-11. Potential-energy (BCS) to kinetic-energy (BEC)-driven pairing in the attractive Hubbard model. https://doi.org/10.1103/physrevb.74.024501

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