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TT: Fachverband Tiefe Temperaturen

TT 3: Correlated Electrons: Spin Systems and Itinerant Magnets 1

TT 3.1: Vortrag

Montag, 23. März 2009, 10:15–10:30, HSZ 304

Plaquette order in the J₁-J₂-J₃ model: a series expansion analysis — •Wolfram Brenig¹ and Marcelo Arlego² — ¹Institut für Theoretische Physik, Technische Universität Braunschweig, Germany — ²Departamento de Física, Universidad Nacional de La Plata, Argentina

Series expansion based on the flow equation method is employed to study the zero temperature properties of the spin-1/2 J₁-J₂-J₃ antiferromagnet in two dimensions. Starting from the exact limit of decoupled plaquettes in a particular generalized J₁-J₂-J₃ model we analyze the evolution of the ground state energy and the elementary triplet excitations in powers of all three inter-plaquette couplings up to fifth order. We find the plaquette phase to remain stable over a wide range of exchange couplings and to connect adiabatically up to the case of the plain J₁-J₂-J₃ model, however not to the J₁-J₂ model at J₃=0. This corroborates other recent predictions. Additionally we estimate the extent of the plaquette phase by Dlog-Padé analysis of the critical lines that result from closure of the triplet gap.