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arXiv 1610.03312cond-mat.str-el
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NiCl2-4SC(NH2)2化合物中磁场诱导有序相的核磁共振研究

Nuclear magnetic resonance study of the magnetic-field-induced ordered phase in the NiCl2-4SC(NH2)2 compound

Rémi Blinder, Maxime Dupont, Sutirtha Mukhopadhyay, Mihael S. Grbić, Nicolas Laflorencie, Sylvain Capponi, Hadrien Mayaffre, Claude Berthier, Armando Paduan-Filho, Mladen Horvatić

摘要:

利用核磁共振(NMR)研究了准一维(准一维)反铁磁量子自旋链化合物NiCl 2 -4SC(NH 2)2(DTN)的玻色-爱因斯坦凝聚相的高磁场(H)部分.我们精确地确定了低至40 mK的相边界Tc(H);临界玻色子密度n_c(Tc);以及极低温(T = 0.12 K)下BEC序参量S_perp的绝对值。所有的结果准确地再现了一个现实的三维(3D)模型哈密顿量的量子蒙特卡罗模拟。基于1D Tomonaga-Luttinger液体描述的近似分析预测被发现对于Tc(H)是精确的,但对于S_perp(H)则不那么精确,S_perp(H)对3D耦合的强度更敏感,特别是接近临界场。基于Hartree-Fock-Popov描述的平均场处理仅在n_c = 4%(T <0.3K)时有效,而在更高的n_c时,玻色子相互作用似乎改变了态密度。

英文摘要:

Nuclear magnetic resonance (NMR) study of the high magnetic field (H) part of the Bose-Einstein condensed (BEC) phase of the quasi-onedimensional (quasi-1D) antiferromagnetic quantum spin-chain compound NiCl2-4SC(NH2)2 (DTN) was performed. We precisely determined the phase boundary, Tc(H), down to 40 mK; the critical boson density, n_c(Tc); and the absolute value of the BEC order parameter S_perp at very low temperature (T = 0.12 K). All results are accurately reproduced by numerical quantum Monte Carlo simulations of a realistic three-dimensional (3D) model Hamiltonian. Approximate analytical predictions based on the 1D Tomonaga-Luttinger liquid description are found to be precise for Tc(H), but less so for S_perp(H), which is more sensitive to the strength of 3D couplings, in particular close to the critical field. A mean-field treatment, based on the Hartree-Fock-Popov description, is found to be valid only up to n_c = 4% (T < 0.3 K), while for higher n_c boson interactions appear to modify the density of states.

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