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Rodríguez Laguna, Javier

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0000-0003-2218-7980
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Rodríguez Laguna
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Javier
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Autor: Santos, Hernán ×

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    Entanglement detachment in fermionic systems
    (Springer, 2018-11-27) Santos, Hernán; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier
    This article introduces and discusses the concept of entanglement detachment. Under some circumstances, enlarging a few couplings of a Hamiltonian can effectively detach a (possibly disjoint) block within the ground state. This detachment is characterized by a sharp decrease in the entanglement entropy between block and environment, and leads to an increase of the internal correlations between the (possibly distant) sites of the block. We provide some examples of this detachment in free fermionic systems. The first example is an edge-dimerized chain, where the second and penultimate hoppings are increased. In that case, the two extreme sites constitute a block which disentangles from the rest of the chain. Further examples are given by (a) a superlattice which can be detached from a 1D chain, and (b) a star-graph, where the extreme sites can be detached or not depending on the presence of an external magnetic field, in analogy with the Aharonov-Bohm effect. We characterize these detached blocks by their reduced matrices, specially through their entanglement spectrum and entanglement Hamiltonian.
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    Engineering large end-to-end correlations in finite fermionic chains
    (American Physical Society., 2018-12-14) Santos, Hernán; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier
    We explore deformations of finite chains of noninteracting fermions at half-filling which give rise to large correlations between their extremes. After a detailed study of the Su-Schrieffer-Heeger model, the tradeoff curve between end-to-end correlations and the energy gap of the chains is obtained using machine-learning techniques, paying special attention to the scaling behavior with the chain length.We find that edge-dimerized chains, where the second and penultimate hoppings are reinforced, are very often close to the optimal configurations. Our results allow us to conjecture that, given a fixed gap, the maximal attainable correlation falls exponentially with the system size. Study of the entanglement entropy and contour of the optimal configurations suggest that the bulk entanglement pattern is minimally modified from the clean case.