Optical sum rule violation and the kinetic energy change at the phase coherence transition in superconductors with pseudogap

T. K. Kopeć

doi:10.1103/PhysRevB.67.014520

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Optical sum rule violation and the kinetic energy change at the phase coherence transition in superconductors with pseudogap

T. K. Kopeć

DOI 10.1103/PhysRevB.67.014520 · Physical Review B

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Abstract

We calculate the spectral weights of the optical conductivity of a three-dimensional lattice version of the “negative-U” Hubbard model of a strongly correlated superconductor in the intermediate to large-U limit. Starting from a tight-binding Fermionic Hamiltonian, we pass to an effective action in terms of the modulus and phase of the superconducting pairing field as the relevant Bosonic variables. Furthermore, we calculate the temperature and U-interaction dependence of the oscillator strength and find that below the pair formation temperature T⋆ the optical integral is not conserved, implying the lowering of the kinetic energy at Tc upon entering the phase coherent superfluid state.