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Center for Nonlinear Studies |
The existence of a decon ned quantum-critical point [1] between the standard antiferromagnet and a valence-bond solid in 2D S=1/2 quantum magnets has been frequently questioned, due to anomalous nite-size scaling behaviors observed in quantum Monte Carlo simulations and interpreted by some as signs of a rst-order transition. I will discuss a new nite-size scaling hypothesis in which the two divergent length scales of the problem (the standard correlation length and a decon nement scale) are treated di erently than in standard scenarios for dangerously irrelevant perturbations (which generate the second length scale in, e.g., classical 3D clock models) [2]. Quantum Monte Carlo simulations of the J-Q model (a Heisenberg model extended with certain multi-spin interactions) are in full agreement with this form, suggesting that decon ned quantum-criticality is an even richer phenomenon than initially thought. Since nite temperature T plays the role of a nite imaginary-time dimension in quantum systems, the anomalous scaling behavior impacts also the scaling in the quantum-critical \fan" at T > 0. This is also observed in the J-Q model.
Host: Shizeng Lin