Universal Behavior of One-Dimensional Gapped Antiferromagnets in a Staggered Magnetic Field
Universal Behavior of One-Dimensional Gapped Antiferromagnets in a Staggered Magnetic Field
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一维带隙反铁磁体在交错磁场中的普遍行为
DOI：
10.1103/physrevlett.80.5786
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发表时间：
1998
影响因子：
8.6
通讯作者：
A. Zheludev
中科院分区：
文献类型：
--
作者：
S. Maslov;A. Zheludev
我们研究了在任意强交错磁场存在下一维带隙海森堡反铁磁体的特性。对于这些系统，我们预测交错磁化曲线的通用形式。该函数以及交错场对纵向和横向激发光谱中能隙的影响是根据 O(3) 对称 1+1 维场论中有效势的通用形式确定的。我们的理论发现与最近 R2BaNiO5（R = 磁性稀土）线性链混合自旋反铁磁体的中子散射数据非常一致。近二十年来，在磁激发谱中具有交换间隙的一维各向同性海森堡反铁磁体一直是理论和实验关注的中心。这类材料包括整数自旋海森堡链[1]（通常称为霍尔丹能隙系统）和具有偶数条腿的半整数自旋梯[2]。由于这些系统中存在强量子涨落，交错磁化强度具有有限的相关长度。激发光谱的主要特征是锐自旋 1 激发的简并三重态，通常称为磁振子，通过有限的能隙 � 与基态分开。近年来，许多工作旨在了解这种带隙一维反铁磁体在外部均匀磁场存在下的行为[3-5]。然而，直接耦合到经典系统的阶次参数的交错场的影响尚未得到足够详细的研究。这主要是因为在微观尺度上调制的强磁场被认为几乎不可能通过实验实现[6]。 R2BaNiO5（R = 磁性稀土）直链镍酸盐的中子散射实验及其对沉浸在强有效交错交换场中的非相互作用霍尔丹自旋链的解释取得了突破[7,8]。在 R2BaNiO5 化合物中，几乎完全各向同性的反铁磁 S = 1 链由 Ni 2+ 离子形成。有效交错场由 R 3+ 亚晶格生成，在低于某个尼尔温度 TN 时，R 3+ 亚晶格会变得磁性有序。交错场强与有序矩的大小成正比
We study the properties of one-dimensional gapped Heisenberg antiferromagnets in the presence of an arbitrary strong staggered magnetic field. For these systems we predict a universal form for the staggered magnetization curve. This function, as well as the effect the staggered field has on the energy gaps in longitudinal and transversal excitation spectra, are determined from the universal form of the effective potential in O(3)-symmetric 1+1–dimensional field theory. Our theoretical findings are in excellent agreement with recent neutron scattering data on R2BaNiO5 (R = magnetic rare earth) linear-chain mixed spin antiferromagnets. One-dimensional isotropic Heisenberg antiferromagnets with an exchange gap in the magnetic excitation spectrum have been at the center of theoretical and experimental attention for almost two decades. This class of materials includes integer-spin Heisenberg chains [1] (commonly referred to as Haldane-gap systems) and halfinteger spin ladders with an even number of legs [2]. Due to the presence of strong quantum fluctuations in these systems the staggered magnetization has a finite correlation length. The principal feature of the excitation spectrum is a degenerate triplet of sharp spin-1 excitations commonly referred to as magnons, separated from the ground state by a finite energy gap �. In recent years much work was aimed at understanding the behavior of such gapped 1D antiferromagnets in the presence of an external uniform magnetic field [3–5]. However, the effect of a staggered field, that couples directly to the order parameter of the classical system, has not been investigated in sufficient detail. This is mainly due to the fact that a strong magnetic field modulated on the microscopic scale was thought to be all but impossible to realize experimentally [6]. A breakthrough came with neutron scattering experiments on R2BaNiO5 (R = magnetic rare-earth) linear-chain nickelates and their interpretation in terms of non-interacting Haldane spin chains immersed in a strong effective staggered exchange field [7,8]. In R2BaNiO5 compounds almost perfectly isotropic antiferromagnetic S = 1 chains are formed by the Ni 2+ ions. The effective staggered field is generated by the R 3+ sublattice that becomes ordered magnetically below some Neel temperature TN. The staggered field intensity is proportional to the magnitude of the ordered moment