Bert F, Bono D, Mendels P, Ladieu F, Duc F, Trombe J-C, Millet P
Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France.
Phys Rev Lett. 2005 Aug 19;95(8):087203. doi: 10.1103/PhysRevLett.95.087203.
The volborthite compound is one of the very few realizations of S=1/2 quantum spins on a highly frustrated kagomé-like lattice. Low-T SQUID measurements reveal a broad magnetic transition below 2 K which is further confirmed by a peak in the 51V nuclear spin relaxation rate (1/T1) at 1.4 K +/- 0.2 K. Through 51V NMR, the ground state (GS) appears to be a mixture of different spin configurations, among which 20% corresponds to a well defined short-range order, possibly of the sqrt(3) x sqrt(3) type. While the freezing involves all the Cu2+ spins, only 40% of the copper moment is actually frozen which suggests that quantum fluctuations strongly renormalize the GS.
钒铜铅矿化合物是在高度受挫的类 Kagomé 晶格上实现 S = 1/2 量子自旋的极少数实例之一。低温超导量子干涉仪测量显示，在 2 K 以下有一个宽泛的磁转变，这在 1.4 K ± 0.2 K 时51V 核自旋弛豫率（1/T1）的峰值中得到进一步证实。通过 51V 核磁共振，基态（GS）似乎是不同自旋构型的混合态，其中 20% 对应于一种明确的短程有序，可能是 sqrt(3) x sqrt(3) 类型。虽然冻结涉及所有 Cu2+ 自旋，但实际上只有 40% 的铜磁矩被冻结，这表明量子涨落强烈重整了基态。
