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DY: Fachverband Dynamik und Statistische Physik

DY 30: Poster II

DY 30.3: Poster

Donnerstag, 29. März 2007, 16:00–18:00, Poster D

Quantum Monte Carlo Investigation of Quantum Phase Transitions of Mixed Heisenberg Spin Chains — •Rainer Bischof¹, Peter Crompton², and Wolfhard Janke¹ — ¹Institut für Theoretische Physik, Universität Leipzig, Germany — ²Center for Theoretical Physics, Massachusetts Institute of Technology, USA

By means of quantum Monte Carlo simulations at low temperatures, the quantum phase transitions in antiferromagnetic Heisenberg spin chains consisting of two different kinds of spin, S_a and S_b, that appear alternatingly in pairs, are investigated for the cases S_a=1/2 and S_b=1, S_a=1/2 and S_b=3/2 as well as S_a=1 and S_b=3/2. Transitions between qualitatively different ground states (quantum phases) are induced by varying the parameter α which is the relative coupling between unlike and like spins. In particular, the so-called twist order parameter as well as spatial and imaginary temporal correlation lengths are measured and analysed. Critical values of α, critical exponents and leading correction terms are extracted by finite-size scaling analysis.