The phase diagram and hidden order for generalized spin ladders

被引:36
作者
Brehmer, S
Mikeska, HJ
Neugebauer, U
机构
[1] Inst. für Theoretische Physik, Universität Hannover
关键词
D O I
10.1088/0953-8984/8/38/018
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
We investigate the phase diagram of antiferromagnetic spin ladders with additional exchange interactions on diagonal bonds by variational and numerical methods. These generalized spin ladders interpolate smoothly between the S = 1/2 chain with competing nn and nnn interactions, the S = 1/2 chain with alternating exchange and the antiferromagnetic (AF) S = 1 chain. The Majumdar-Ghosh ground states are formulated as matrix product states and are shown to exhibit the same type of hidden order as the AF S = 1 chain. Generalized matrix product states are used for a variational calculation of the ground state energy and the spin and string correlation functions. Numerical (Lanczos) calculations of the energies of the ground state and of the low-lying excited states are performed, and compare reasonably with the variational approach. Our results support the hypothesis that the dimer and Majumdar-Ghosh points are in the same phase as the AF S = 1 chain.
引用
收藏
页码:7161 / 7177
页数:17
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