Bose Glass-BEC Transition of Magnons in Tl_1-xK_xCuCl₃

2010/06/03 by Fumiko Yamada, Yamada, Fumiko, Hidekazu Tanaka +5
Physics and Astronomy · #Optical properties and cooling technologies in crystalline materials #Cold Atom Physics and Bose-Einstein Condensates #Quantum, superfluid, helium dynamics

paper · pdf · doi:10.48550/arxiv.1006.0584

Abstract

We report the magnetic-field induced Bose glass-BEC transition of magnons in Tl_1-xK_xCuCl₃ and its critical behavior investigated through specific heat and ESR measurements. The field dependence of the BEC transition temperature T_{\rm N} can be described by the power law [H - H_{\rm c}] ∝ T_{\rm N}^ϕ near the quantum critical point H_{\rm c} ∼ 3.5 T. The critical exponent ϕ tends to reach a value smaller than 1/2 with decreasing fitting window in contrast with ϕ→ 3/2 for the standard BEC in pure system. At sufficiently low temperatures, the ESR line shape for H ≃ H_{\rm c} is intermediate between Gaussian and Lorentzian. This indicates the localization of magnons for H

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