Entanglement spectrum of the degenerative ground state of Heisenberg ladders in a time-dependent magnetic field
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Date
2017-11-14
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Journal ISSN
Volume Title
Journal Title
EPL (Europhysics Letters)
Volume Title
119
Article Title
57003
Publisher
Institute of Physics Publishing
Abstract
We investigate the relationship between the entanglement and subsystem Hamiltonians in the perturbative regime of strong coupling between subsystems. One of the two conditions that guarantees the proportionality between these Hamiltonians obtained by using the nondegenerate perturbation theory within the first order is that the unperturbed ground state has a trivial entanglement Hamiltonian. Furthermore, we study the entanglement Hamiltonian of the Heisenberg ladders in a time-dependent magnetic field using the degenerate perturbation theory, where couplings between legs are considered as a perturbation. In this case, when the ground state is twofold degenerate, and the entanglement Hamiltonian is proportional to the Hamiltonian of a chain within first-order perturbation theory, even then also the unperturbed ground state has a nontrivial entanglement spectrum.