Sign change of the extendeds-wave pairing vertex in the dynamic Hubbard model: A quantum Monte Carlo study

K. Bouadim, M. Enjalran, F. Hébert, G. G. Batrouni, R. T. Scalettar
2008 Physical Review B  
The 'dynamic' Hubbard Hamiltonian describes interacting fermions on a lattice whose on-site repulsion is modulated by a coupling to a fluctuating bosonic field. We investigate one such model, introduced by Hirsch, using the determinant Quantum Monte Carlo method. Our key result is that the extended s-wave pairing vertex, repulsive in the usual static Hubbard model, becomes attractive as the coupling to the fluctuating Bose field increases. The sign problem prevents us from exploring a low
more » ... ploring a low enough temperature to see if a superconducting transition occurs. We also observe a stabilization of antiferromagnetic correlations and the Mott gap near half-filling, and a near linear behavior of the energy as a function of particle density which indicates a tendency toward phase separation.
doi:10.1103/physrevb.77.014516 fatcat:xlw5wbxtvreutp6sgu242rs3ri