Abstract
Bipartite entanglement in the ground state of a chain of 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 consists of a comb of spins, spaced sites apart. Our results are thus not restricted to a simple area law, but contain nonlocal information, parametrized by the spacing . For the model we calculate the von Neumann entropy analytically when and investigate its dependence on and . We find that an external magnetic field induces an unexpected length scale for entanglement in this case.
- Received 5 April 2006
DOI:https://doi.org/10.1103/PhysRevA.74.012311
©2006 American Physical Society