Andreas Giesekus | Searcharxiv

arXiv1995

Low-energy states for correlated-electron models in the strong-coupling limit

We study a class of exactly solvable models for strongly correlated electrons, defined on a set of N cells, and with infinite on-site repulsion on part of the sites of each cell. For 2N or more electrons the exact ground state is known. We construct a tractable (2N-1)-particle state which becomes asymptotically degenerate to the ground state in the thermodynamic limit for one special D-dimensional model. For other models, that state may be used to calculate variational upper bounds on the ground-state energy. For a Hubbard chain with three sites per unit cell, the analytical bound is compared to numerically exact results.

cond-mat↗

arXiv1995

Dynamical correlations in a Hubbard chain with resonating-valence-bond ground state

Dynamical correlation functions for temperature T=0 are calculated for a Hubbard chain with infinite on-site repulsion. This chain contains three sites per unit cell and has a known resonating-valence-bond ground state for a filling of 2 particles per unit cell. A finite system of 24 sites is studied numerically. The recursion method is applied and results for spectral densities are compared to variationally calculated excited-state eigenvalues. Charge and spin degrees of freedom located at the backbone sites are considered. The spectral densities show dispersionless excitations. The energy spectrum displays a gap indicating an insulating ground state. Spectral functions for the propagation of a single hole in a resonating-valence-bond background are provided and indicate delocalized dispersive hole excitations.

cond-mat↗