Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Statistical Physics (general)

DY 13.7: Vortrag

Montag, 7. März 2016, 16:30–16:45, H48

Apparent non-universality due to competing anisotropies in 3D Zq models — •Thomas Lottermoser¹, Andres Cano², and Manfred Fiebig¹ — ¹Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland — ²CNRS, Université de Bordeaux, ICMCB, UPR 9048, 33600 Pessac, France

3D Z_q models (q>4) like the q-state clock model, antiferromagnetic Potts model or the XY model with discrete q-fold anisotropy, are known to belong all to the XY-universality class at criticality, whereas the Z_q anisotropy is dangerously irrelevant at T_C. This leads to a new length scale associated to the fluctuations of the phase of the order parameter with a critical exponent ν_q>ν. Here ν is the standard XY critical exponent for the correlation length ξ of the order parameter amplitude. While there is a general agreement on this behavior in the literature, due to contradicting simulation results the question of the universality of ν_q aroused. We propose that these contradictions can be explained by the existence of competing anisotropies. Therefore, in our extensive Monte-Carlo study we investigated the critical behavior of a 12-state clock model with competing 6-fold anisotropy. As a result we found that the apparent non-universality of ν_q can indeed be traced back to the strength of the competing anisotropy we introduced in our model system. This allows us to continuously tune the value of ν_q between the universal values for the 6-state and 12-state clock models, respectively.