Electron Phase Separations Involving Superconductivity in the Extended Hubbard Models with Pair Hopping Interaction

Abstract

In this work the extended Hubbard models with pair hopping interaction (at the atomic limit) are investigated within the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-eld approximation (exact in d → +∞). We analyze mutual stability of the superconducting phase and charge or (ferro/antiferro-)magnetic orderings as well as homogeneous mixed phases. Our preliminary results for U = 0 show that the superconducting phase can coexist with the charge or (ferro/antiferro-)magnetic phases only in states with electron phase separation.

Phase Separation of Superconducting Phases in the Penson–Kolb–Hubbard Model

“…Let us stress that it has been reported that superconductivity can coexist with charge-ordered and magnetically ordered phases in states with phase separations [32,36,37,67,68]. In present work we do not consider the charge and magnetic orderings.…”

“…The pair-hopping term (J) was first proposed in Refs. [29 and 30] by Penson and Kolb in 1986 and it can be derived from a general microscopic tight-binding Hamiltonian, where the Coulomb repulsion may lead to the pair hopping interaction J = ii|e 2 /r|jj [17][18][19][20][21][22][23][32][33][34][35][36][37][38]. In such a case J is positive (repulsive model J > 0, favoring η-wave SC), but in this case the magnitude of J is very small.…”

“…Ref. [17][18][19][20][21][22][23][32][33][34][35][36][37][38] and references therein). It can also be included in the effective models for Fermi gas in an optical lattice in the strong interaction limit [39].…”

“…In the limit U/t → −∞ the discontinuous boundary between both SS phases is located at J/t = 0 (independently of µ). In such a limit there is a full symmetry between s-wave SS and η-wave SS phases [32][33][34][35][36][37]. Notice also that in this limit model (1) is equivalent with the hard-core boson model on the lattice [17,32].…”

Various Charge-Ordered States in the Extended Hubbard Model with On-Site Attraction in the Zero-Bandwidth Limit

“…This interplay can lead to either mutual enhancement or reduction of mentioned phenomena, e.g. [10][11][12][13][14][15]20]. Moreover, various types of charge-order exist in superconducting and multiferroic materials.…”