title: Two-site entropy and quantum phase transitions in low-dimensional models.
abstract: We propose a new approach to study quantum phase transitions in low-dimensional lattice models. It is based on studying the von Neumann entropy of two neighboring central sites in a long chain. It is demonstrated that the procedure works equally well for fermionic and spin models, and the two-site entropy is a better indicator of quantum phase transition than calculating gaps, order parameters, or the single-site entropy. The method is especially convenient when the density-matrix renormalization-group algorithm is used.
authors.affiliation: Research Institute for Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary.
authors.forename: O
authors.initials: O
authors.lastname: Legeza
authors.forename: J
authors.initials: J
authors.lastname: Sólyom