Possible New Vortex Matter Phases inBi2Sr2CaCu2

Abstract

The vortex matter phase diagram of Bi 2 Sr 2 CaCu 2 O 8 crystals is analyzed by investigating vortex penetration through the surface barrier in the presence of a transport current. The strength of the effective surface barrier and its nonlinearity and asymmetry are used to identify a possible new ordered phase above the first-order transition. This technique also allows sensitive determination of the depinning temperature. The solid phase below the firstorder transition is apparently subdivided into two phases by a vertical line extending from the multicritical point.

Ginzburg-Landau theory of type II superconductors in magnetic field

“…The resulting maximum at which the magnetization and the entropy jump vanish is a Kauzmann point . This universal "order -disorder" transition line (ODT), which appeared first in the strongly layered superconductors (BSCCO (Fuchs et al, 1998)) was extended to the moderately anisotropic superconductors (LaSCCO (Radzyner et al, 2002)) and to the more isotropic ones like Y BCO Pal et al, 2001Pal et al, , 2002. The symmetry characterization of the transition is clear: spontaneous breaking of both the continuous translation and the rotation symmetries down to a discrete symmetry group of the lattice.…”

“…Experiments in BSCCO (Beidenkopf et al, 2005(Beidenkopf et al, , 2007Fuchs et al, 1998) indicate that the line crosses the ODT line right at its maximum, continues deep into the ordered (Bragg) phase. This proximity of the glass line to the Kauzmann point is reasonable since both signal the region of close competition of the disorder and the thermal fluctuations effects.…”

“…To summarize we have several transition lines 1) The first order (Bouquet et al, 2001;Schilling et al, 1996Schilling et al, , 1997Zeldov et al, 1995) melting line due to thermal fluctuations was shown to merge with the "second magnetization peak" line due to pinning forming the universal order -disorder phase transition line (Fuchs et al, 1998;Radzyner et al, 2002). At the low temperatures the location of this line strongly depends on disorder and generally exhibits a positive slope (termed also the "inverse" melting (Paltiel et al, 2000a,b)), while in the "melting" section it is dominated by thermal fluctuations and has a large negative slope.…”

Effects of Point Defects on the Phase Diagram of Vortex States in High-TcSuperconductors in theB‖<

“…Similar anomalies were also observed in BSCCO. [22][23][24][25] In the present Letter, we compose the phase diagram in the pinning-strength (ǫ)-temperature (T ) plane ( phases as in pure systems. [26,27] A first-order transition line stretches from the melting line into the VL region dividing the VS and VL phases.…”

Third harmonics due to surface barrier in high-temperature superconductor

“…[1][2][3][4][5][6][7][8] Experiments show that there exists a surface zone with a higher critical current density j c ͑larger than the inside one͒ which may originate from the surface pinning, the Bean-Livingston barrier, or the geometrical barrier. [9][10][11][12][13][14][15] We have proposed a model to describe the surface barrier ͑SB͒ and studied the influence of SB on the fundamental ac susceptibility ͑ACS͒.…”