Frustrated Heisenberg antiferromagnets: Fluctuation-induced first order vs. deconfined quantum criticality

¹ Instituut-Lorentz, Universiteit Leiden - P.O. Box 9506 2300 RA Leiden, The Netherlands
² Institut für Theoretische Physik, Universität zu Köln Zülpicher Str. 77, D-50937 Köln, Germany

Received: 11 January 2006
Accepted: 7 April 2006

Abstract

Recently it was argued that quantum phase transitions can be radically different from classical phase transitions with, as a highlight, the “deconfined critical points” exhibiting fractionalization of quantum numbers due to Berry phase effects. Such transitions are supposed to occur in frustrated (“J₁-J₂”) quantum magnets. We have developed a novel renormalization approach for such systems which is fully respecting the underlying lattice structure. According to our findings, another profound phenomenon is around the corner: a fluctuation-induced (order-out-of-disorder) first-order transition. This has to occur for large spin and we conjecture that it is responsible for the weakly first-order behavior recently observed in numerical simulations for frustrated systems.