INVESTIGADORES
CANOSA Norma Beatriz
artículos
Título:
Generalized mean-field description of entanglement in dimerized spin systems
Autor/es:
A. BOETTE; R. ROSSIGNOLI; N. CANOSA; J.M. MATERA
Revista:
PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS
Editorial:
APS
Referencias:
Lugar: New York; Año: 2015 vol. 91 p. 644281 - 6442812
ISSN:
0163-1829
Resumen:
We discuss a generalized self-consistent mean-field (MF) treatment, based on the selection of an arbitrary
subset of operators for representing the system density matrix, and its application to the problem of entanglement
evaluation in composite quantum systems. As a specific example, we examine in detail a pair MF approach to the
ground state (GS) of dimerized spin-1/2 systems with anisotropic ferromagnetic-type XY and XYZ couplings in
a transverse field, including chains and arrays with first neighbor and also longer range couplings. The approach
is fully analytic and able to capture the main features of the GS of these systems, in contrast with the conventional
single-spin MF. Its phase diagram differs significantly from that of the latter, exhibiting (Sz) parity breaking just
in a finite field window if the coupling between pairs is sufficiently weak, together with a fully dimerized phase
below this window and a partially aligned phase above it. It is then shown that through symmetry restoration,
the approach is able to correctly predict not only the concurrence of a pair, but also its entanglement with the
rest of the chain, which shows a pronounced peak in the parity breaking window. Perturbative corrections allow
to reproduce more subtle observables like the entanglement between weakly coupled spins and the low lying
energy spectrum. All predictions are tested against exact results for finite systems.