Dmitriev D V, Ya Krivnov V
Institute of Biochemical Physics of RAS, Kosygin str. 4, 119334, Moscow, Russia.
J Phys Condens Matter. 2016 Dec 21;28(50):506002. doi: 10.1088/0953-8984/28/50/506002. Epub 2016 Oct 21.
We consider analytically and numerically an anisotropic spin-[Formula: see text] delta-chain (sawtooth chain) in which exchange interactions between apical and basal spins are ferromagnetic and those between basal spins are antiferromagnetic. In the limit of strong anisotropy of exchange interactions this model can be considered as the Ising delta chain with macroscopic degenerate ground state perturbed by transverse quantum fluctuations. These perturbations lift the ground state degeneracy and the model reduces to the basal XXZ spin chain in the magnetic field induced by static apical spins. We show that the ground state of such a model is ferrimagnetic. The excitations of the model are formed by ferrimagnetic domains separated by domain walls with a finite energy. At low temperatures the system is effectively divided into two independent subsystems, the apical subsystem described by the Ising spin-[Formula: see text] chain and the basal subsystem described by the XXZ chain with infinite zz interactions.
我们通过解析和数值方法研究了一种各向异性的自旋 - [公式：见文本] 三角链（锯齿链），其中顶端自旋和基底自旋之间的交换相互作用是铁磁性的，而基底自旋之间的交换相互作用是反铁磁性的。在交换相互作用的强各向异性极限下，该模型可被视为具有宏观简并基态且受横向量子涨落扰动的伊辛三角链。这些扰动消除了基态简并性，并且该模型简化为由静态顶端自旋诱导的磁场中的基底XXZ自旋链。我们表明这种模型的基态是亚铁磁性的。该模型的激发由具有有限能量的畴壁分隔的亚铁磁畴形成。在低温下，系统有效地分为两个独立的子系统，由伊辛自旋 - [公式：见文本] 链描述的顶端子系统和由具有无限zz相互作用的XXZ链描述的基底子系统。
