具有循环四自旋交换的两足阶梯中的基态保真度和量子临界性
Ground-state fidelity and quantum criticality in a two-leg ladder with cyclic four-spin exchange
摘要：
利用新发展的张量网络算法研究了具有循环四自旋交换的两条腿海森堡自旋梯。该算法可以有效地计算每个格点的基态保真度，这使我们能够建立量子晶格多体系统的基态相图。后者是基于这样的观察，即对于一个无限大的系统，任何奇异性的基态保真度表面的特点是一个临界点，在该系统进行相变。对于具有循环四自旋交换的两腿海森堡自旋1/2阶梯，确定了六个不同的相：铁磁相、梯级单重态相、交错二聚体相、标量手性相、主导矢量手性区和主导共线自旋区。我们的结果与前人的精确对角化和密度矩阵重整化群的结果一致。
英文摘要：
We investigate a two-leg Heisenberg spin ladder with cyclic four-spin exchange by exploiting a newly-developed tensor network algorithm. The algorithm allows to efficiently compute the ground-state fidelity per lattice site, which enables us to establish the ground-state phase diagram for quantum lattice many-body systems. The latter is based on the observation that, for an infinite-size system, any singularity on a ground-state fidelity surface characterizes a critical point, at which the system undergoes a phase transition. For the two-leg Heisenberg spin-1/2 ladder with cyclic four-spin exchange, six different phases are identified: the ferromagnetic phase, the rung singlet phase, the staggered dimer phase, the scalar chirality phase, the dominant vector chirality region, and the dominant collinear spin region. Our findings are in a good agreement with the previous studies from the exact diagonalization and the density-matrix renormalization group.
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