J. Ranninger

TL;DR: In this paper, the authors review the thermodynamic and electromagnetic properties of such systems in several limiting scenarios: (i) systems with on-site pairing which can be described by the extended negative-$U$ Hubbard model, at which it reduces to a system of tightly bound electron pairs (bipolarons) on a lattice, and the changeover from weak-attraction BCS-like superconductivity to the superfluidity of charged hard core bosons is examined.

TL;DR: In this article, the authors examined the electronic excitation spectrum of a bipolaronic crystal and showed that in the low bipolaron density limit the spectrum is superfluidlike, so that bipolarons might be superconducting.

TL;DR: In this paper, a phase diagram for all the possible collinear spin arrangements for a particular magnetic and orbital order is derived within the atomic limit, and the experimentally observed magnetic order falls into a region of values of these parameters which are expected for the magnetic structure of a particular spin arrangement.

TL;DR: It turns out that quantum fluctuations stabilize the homogeneous superconducting phase and suppress charge order, and the specific heats in the normal state for narrow-band bosons and fermions on a lattice are practically identical.

TL;DR: A generalized periodic Anderson model with on-site hybridization between wide- and narrow-band electrons and strong and local coupling with the lattice deformation is studied and an effective Hamiltonian is obtained which describes a contact interaction between local pairs and wide- band electrons as well as the direct hopping of local Pair hopping and interparticle Coulomb interactions.