title: Anisotropy and magnetic field effects on the entanglement of a two qubit Heisenberg XY chain.
abstract: We investigate the entanglement of a two-qubit anisotropic Heisenberg XY chain in thermal equilibrium at temperature T in the presence of an external magnetic field B along the z axis. By means of the combined influences of anisotropic interactions and a magnetic field B, one is able to produce entanglement for any finite T, by adjusting the magnetic field strength. This contrasts with the isotropic interaction or the B = 0 cases, for which there is no entanglement above a critical temperature T(c) that is independent of the external B field.
authors.affiliation: Department of Physics and Astronomy, The University of Nebraska, 116 Brace Laboratory, Lincoln, Nebraska 68588-0111, USA.
authors.forename: G
authors.initials: G
authors.lastname: Lagmago Kamta
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Starace