Fate of the peak effect in a type-II superconductor: multicriticality in the Bragg-Glass transition |
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Authors: | Park S R Choi S M Dender D C Lynn J W Ling X S |
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Institution: | Department of Physics, Brown University, Providence, Rhode Island 02912, USA. |
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Abstract: | We have used small-angle neutron scattering (SANS) and ac magnetic susceptibility to investigate the global magnetic field H vs temperature T phase diagram of a Nb single crystal in which a first-order transition of Bragg-glass melting (disordering), a peak effect, and surface superconductivity are all observable. It was found that the disappearance of the peak effect is directly related to a multicritical behavior in the Bragg-glass transition. Four characteristic phase boundary lines have been identified on the H-T plane: a first-order line at high fields, a mean-field-like continuous transition line at low fields, and two continuous transition lines associated with the onset of surface and bulk superconductivity. All four lines are found to meet at a multicritical point. |
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