Hagiwara M, Regnault L P, Zheludev A, Stunault A, Metoki N, Suzuki T, Suga S, Kakurai K, Koike Y, Vorderwisch P, Chung J-H
RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan.
Phys Rev Lett. 2005 May 6;94(17):177202. doi: 10.1103/PhysRevLett.94.177202. Epub 2005 May 4.
Inelastic neutron scattering experiments on the S = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9D24N4)(NO2)ClO4 have been performed under magnetic fields below and above a critical field Hc at which the energy gap closes. Normal field dependence of Zeeman splitting of the excited triplet modes below Hc has been observed, but the highest mode is unusually small and smears out with increasing field. This can be explained by an interaction with a low-lying two magnon continuum at q(parallel) = pi that is present in dimerized chains but absent in uniform ones. Above Hc, we find only one excited mode, in stark contrast with three massive excitations previously observed in the structurally similar Haldane-gap material NDMAP [A. Zheludev, Phys. Rev. B 68, 134438 (2003)].
在临界场(H_c)上下的磁场条件下，对(S = 1)准一维键交替反铁磁体(Ni(C_9D_{24}N_4)(NO_2)ClO_4)进行了非弹性中子散射实验，其中(H_c)是能隙闭合时的磁场。在(H_c)以下，观测到了激发三重态模式的塞曼分裂的正常场依赖性，但最高模式异常小，并随着磁场增加而展宽。这可以通过与(q_{(\parallel)} = \pi)处的低能双磁振子连续体相互作用来解释，这种相互作用存在于二聚化链中，而在均匀链中不存在。在(H_c)以上，我们只发现了一个激发模式，这与之前在结构相似的具有霍尔丹能隙的材料(NDMAP) [A. 热卢杰夫，《物理评论B》68, 134438 (2003)] 中观测到的三个有质量激发形成了鲜明对比。
