Numéro |
J. Phys. I France
Volume 1, Numéro 5, May 1991
|
|
---|---|---|
Page(s) | 647 - 657 | |
DOI | https://doi.org/10.1051/jp1:1991109 |
DOI: 10.1051/jp1:1991109
J. Phys. I France 1 (1991) 647-657
Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, D-W 5000 Köln 41, Germany
© Les Editions de Physique 1991
J. Phys. I France 1 (1991) 647-657
Extended proof of long-range order in the two-dimensional quantum spin-1/2 XXZ-model at T=0
Hans-Aloys Wischmann and Erwin Müller-HartmannInstitut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, D-W 5000 Köln 41, Germany
(Received 25 January 1991, accepted 1 February 1991)
Abstract
We prove the existence of long-range order (LRO) in the ground state of the 2D quantum spin-1/2
XXZ-model for all anisotropies
and
. We achieve this extension of previous proofs by developing an improved variant of the Dyson-Lieb-Simon proof of LRO in quantum
spin systems and by deriving improved upper and lower bounds for the ground state energy of the
XXZ-model.
© Les Editions de Physique 1991