Comb entanglement in quantum spin chains
Comb entanglement in quantum spin chains
复制标题
量子自旋链中的梳状纠缠
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
M. Novaes
中科院分区：
文献类型：
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作者：
J. Keating;F. Mezzadri;M. Novaes
N个量子自旋链基态中的二体纠缠可以通过计算两两并发度或将链分成两个互补的子系统来量化。在后一种情况下，较小的子系统通常是单个自旋或一组相邻的自旋，纠缠区分为临界和非临界区域。在这里，我们通过考虑更一般的设置来扩展这种方法：我们的较小的子系统S{子A}由L自旋的梳子组成，间隔p个位置。因此，我们的结果并不局限于简单的面积定律，而是包含了非局域信息，用间距p来参数化。对于XX模型，我们解析地计算了当N{屈服}{无穷大}时的von Neumann熵，并研究了它与L和p的依赖关系。我们发现在这种情况下，外加磁场会引起一个意想不到的纠缠长度尺度。
Bipartite entanglement in the ground state of a chain of N quantum spins can be quantified either by computing pairwise concurrence or by dividing the chain into two complementary subsystems. In the latter case the smaller subsystem is usually a single spin or a block of adjacent spins and the entanglement differentiates between critical and noncritical regimes. Here we extend this approach by considering a more general setting: our smaller subsystem S{sub A} consists of a comb of L spins, spaced p sites apart. Our results are thus not restricted to a simple area law, but contain nonlocal information, parametrized by the spacing p. For the XX model we calculate the von Neumann entropy analytically when N{yields}{infinity} and investigate its dependence on L and p. We find that an external magnetic field induces an unexpected length scale for entanglement in this case.