In order to investigate the thermodynamic vortex matter phase diagram the vortex lattice has to be in an equilibrium state. At low temperatures below the irreversibility line the lattice is usually not in thermal equilibrium due to strong pinning and large magnetic hysteresis. In order to resolve the thermodynamic properties, we relaxed the hysteretic magnetization in BSCCO crystals by ‘vortex shaking’ using an in-plane ac field . The resulting reversible magnetization displays a sharp cusp apparently revealing a thermodynamic second-order glass-transition line that intersects the first-order line .
At fields above the first-order melting this second-order transition line, apparently separates a vortex liquid from an amorphous vortex glass. At lower fields, surprisingly, the second-order line appears to bisect the Bragg glass region into two distinct phases. This finding implies that the vortex matter displays four thermodynamic phases the nature of which requires further investigation.
Temperature dependence of the reversible local magnetization in the presence of an in-plane shaking field. A sharp cusp appears reversibly at fields both above the melting line (a) as well as below it (b), marking a second-order glass transition Tg.
Thermodynamic vortex phase diagram in BSCCO consists of a first-order melting line and apparently a second-order glass transition line giving rise to four distinct phases.
- 'Inverse' melting of a vortex lattice
Nurit Avraham, Boris Khaykovich, Yuri Myasoedov, Michael Rappaport, Hadas Shtrikman, Dima E. Feldman, Tsuyoshi Tamegai, Peter H. Kes, Ming Li, Marcin Konczykowski, Kees van der Beek and Eli Zeldov
Nature 411, pp. 451 - 454 (2001)
- Equilibrium first-order melting and second-order glass transitions of the vortex matter in Bi2Sr2CaCu2O8
H. Beidenkopf, N. Avraham, Y. Myasoedov, H. Shtrikman, E. Zeldov, B. Rosenstein, E. H. Brandt, and T. Tamegai
Phys. Rev. Lett. 95, 257004, pp. 1-4 (2005)..