M. Acquarone et al., Electronic and phononic states of the Holstein-Hubbard dimer of variable length: A variational approach, J SUPERCOND, 12(1), 1999, pp. 229-230
A polaronic Hamiltonian is obtained for a dimer of length a, including an E
instein phonon of frequency Omega, a Holstein coupling g(0), and all the el
ectronic one- and two-body terms consistent with a single orbital per site
(the latter evaluated in terms of Wannier functions built from Gaussian ato
mic orbitals). In the quarter- and half-filled orbital cases, the possible
ground states for varying a, at given g(0) and Omega, are identified by ind
ependent and simultaneous optimization of the electronic and phononic param
eters.