Phys. Rev. A 69, 022107 (2004) [4 pages]Entanglement in a second-order quantum phase transitionReceived 23 May 2003; published 18 February 2004 We consider a system of mutually interacting spins 1/2 embedded in a transverse magnetic field which undergoes a second-order quantum phase transition. We analyze the entanglement properties and the spin squeezing of the ground state and show that, contrarily to the one-dimensional case, a cusplike singularity appears at the critical point λc in the thermodynamical limit. We also show that there exists a value λ0>~λc above which the ground state is not spin squeezed despite a nonvanishing concurrence. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevA.69.022107
DOI:
10.1103/PhysRevA.69.022107
PACS:
03.65.Vf, 03.67.Mn, 73.43.Nq
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