Persona:
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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2018 - 201922020 - 20232
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Autor: Alvarellos Bermejo, José Enrique ×

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Mostrando 1 - 4 de 4
  • Miniatura
    Publicación
    Ergotropy and entanglement in critical spin chains
    (American Physical Society, 2023-02-08) Mula, Begoña; Fernández, Julio J.; Santalla, Silvia N.; Alvarellos Bermejo, José Enrique; García Aldea, David; Rodríguez Laguna, Javier; Fernández Sánchez, Evamaría
    A subsystem of an entangled ground state (GS) is in a mixed state. Thus, if we isolate this subsystem from its surroundings, we may be able to extract work applying unitary transformations, up to a maximal amount which is called ergotropy. Once this work has been extracted, the subsystem will still contain some bound energy above its local GS, which can provide valuable information about the entanglement structure. We show that the bound energy for half a free fermionic chain decays as the square of the entanglement entropy divided by the chain length, thus approaching zero for large system sizes, and we conjecture that this relation holds for all one-dimensional critical states.
  • No hay miniatura disponible
    Publicación
    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.
  • Miniatura
    Publicación
    Nanowire reconstruction under external magnetic fields
    (AIP, 2020-12-23) Santalla, Silvia N.; Rodríguez Laguna, Javier; Fernández Sánchez, Evamaría; Alvarellos Bermejo, José Enrique; Rodríguez Laguna, Javier; Fernández Sánchez, Evamaría
    We consider the different structures that a magnetic nanowire adsorbed on a surface may adopt under the influence of external magnetic or electric fields. First, we propose a theoretical framework based on an Ising-like extension of the 1D Frenkel–Kontorova model, which is analyzed in detail using the transfer matrix formalism, determining a rich phase diagram displaying structural reconstructions at finite fields and an antiferromagnetic–paramagnetic phase transition of second order. Our conclusions are validated using ab initio calculations with density functional theory, paving the way for the search of actual materials where this complex phenomenon can be observed in the laboratory.
  • Miniatura
    Publicación
    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.