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Magentic-Field Induced Quantum Phase Transition and Critical Behavior in a Gapped Spin System TlCuCl$_3$

F. Yamada·T. Ono·M. Fujisawa·H. Tanaka·T. Sakakibara
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Abstract

Magnetization measurements were performed on TlCuCl$_3$ with gapped ground state. The critical density and the magnetic phase diagram were obtained. The interacting constant was obtained as $U/k_{\rm B} = 313$ K. The experimental phase boundary for $T < 5$ K agrees perfectly with the magnon BEC theory based on the Hartree-Fock approximation with realistic dispersion relations and $U/k_{\rm B} = 320 $ K. The exponent $ϕ$ obtained with all the data points for $T < 5$ K is $ϕ= 1.99$, which is somewhat larger than theoretical exponent $ϕ_{\rm BEC} =3/2$. However, it was found that the exponent converges at $ϕ_{\rm BEC} =3/2$ with decreasing fitting window.

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F. Yamada, T. Ono, M. Fujisawa, H. Tanaka, T. Sakakibara. 2006-07-18. Magentic-Field Induced Quantum Phase Transition and Critical Behavior in a Gapped Spin System TlCuCl$_3$. https://doi.org/10.1016/j.jmmm.2006.10.372

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