Elementary excitations in the gapped phase of a frustrated S=1/2 spin ladder: from spinons to the Haldane triplet

被引:29
作者
Brehmer, S
Kolezhuk, AK
Mikeska, HJ
Neugebauer, U
机构
[1] Univ Hannover, Inst Theoret Phys, D-30167 Hannover, Germany
[2] Natl Acad Sci Ukraine, Inst Magnetism, UA-252142 Kiev, Ukraine
[3] Minist Educ Ukraine, UA-252142 Kiev, Ukraine
关键词
D O I
10.1088/0953-8984/10/5/017
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
We use the variational matrix-product ansatz to study elementary excitations in the S = 1/2 ladder with additional diagonal coupling, equivalent to a single S = 1/2 chain with alternating exchange and next-nearest-neighbour interaction. In the absence of alternation, the elementary excitation consists of two free S = 1/2 particles ('spinons') which are solitons in the dimer order. When the nearest-neighbour exchange alternates, the 'spinons' are confined into one S = 1 excitation which is a soliton in the generalized string order. The variational results are found to be in qualitative agreement with the exact-diagonalization data for 24 spins. We argue that such an approach gives a reasonably good description over a wide range of the model parameters.
引用
收藏
页码:1103 / 1116
页数:14
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