Abstract
A magnetic field penetrates a superconductor through an array of ‘vortices’, each of which carries one quantum of flux that is surrounded by a circulating supercurrent. In this vortex state, the resistivity is determined by the dynamical properties of the vortex ‘matter’. For the high-temperature copper oxide superconductors (see ref.1 for a theoretical review), the vortex phase can be a ‘solid’, in which the vortices are pinned, but the solid can ‘melt’ into a ‘liquid’ phase, in which their mobility gives rise to a finite resistance. (This melting phenomenon is also believed to occur in conventional superconductors, but in an experimentally inaccessible part of the phase diagram2.) For the case of YBa2Cu3O7, there are indications of the existence of a critical point, at which the character of the melting changes3,4,5,6,7,8,9,10. But neither the thermodynamic nature of the melting, nor the phase diagram in the vicinity of the critical point, has been well established. Here we report measurements of specific heat and magnetization that determine the phase diagram in this material to 26 T, well above the critical point. Our results reveal the presence of a reversible second-order transition above the critical point. An unusual feature of this transition—namely, that the high-temperature phase is the less symmetric in the sense of the Landau theory11—is in accord with theoretical predictions12,13,14 of a transition to a second vortex-liquid phase.
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References
Blatter, G., Feigel’man, M. V., Geshkenbein, V. B., Larkin, A. I. & Vinokur, V. M. Vortices in high-temperature superconductors. Rev. Mod. Phys. 66, 1125–1388 (1994).
Eilenberger, G. Thermodynamic fluctuations of the order parameter in type-II superconductors near the upper critical field H c2. Phys Rev. 164, 628–635 (1967).
Safar, H. et al. Experimental evidence for a multicritical point in the magnetic phase diagram for the mixed state of clean, untwinned YBa2Cu3O7. Phys. Rev. Lett. 70, 3800–3803 (1993).
Nishizaki, T., Naito, T. & Kobayashi, N. Anomalous magnetization and field-driven disordering transition of a vortex lattice in untwinned YBa2Cu3Oy. Phys. Rev. B 58, 11169–11172 (1998).
Roulin, M., Junod, A., Erb, A. & Walker, E. Calorimetric transitions on the melting line of the vortex system as a function of oxygen deficiency in high purity YBa2Ca3Ox. Phys. Rev. Lett. 80, 1722–1725 (1998).
Roulin, M. et al. in Physics and Materials Science of Vortex State, Flux Pinning and Dynamics (eds Kossowsky, R. et al.) 489–504 (Kluwer Academic, Dordrecht, 1999).
Billon, B. Étude Microcalorimétrique et Magnétique du Diagramme de Phase des Composes YBa2Cu3O7- et HgBa2CuO4+., Thesis, Univ. Grenoble 1 (1998).
Bouquet, F. Étude thermodynamique de l'état mixte dans YBa2Cu3O7-x . Thesis, Univ. Grenoble 1 (1998).
Bouquet, F. et al. in Physics and Materials Science of Vortex State, Flux Pinning and Dynamics (eds Kossowsky, R. et al.) 743–758 (Kluwer Academic, Dordrecht, 1999).
Marcenat, C. et al. The vortex state of YBa2Cu3O7-δ: phase diagram; calorimetric and magnetic properties. Physica C 341–348, 949–952 (2000).
Landau, L. D. & Lifshitz, E. M. in Course of Theoretical Physics 2nd edn Vol. 5, Statistical Physics Ch. VIII 257 (Pergamon, Oxford, 1969).
Tešanović, Z. Low-magnetic-field critical behavior in strongly type-II superconductors. Phys. Rev. B 51, 16204–16210 (1995).
Tešanović, Z. Extreme type-II superconductors in a magnetic field: A theory of critical fluctuations. Phys. Rev. B 59, 6449–6474 (1999).
Nguyen, A. K. & Sudbø, A. Topological phase fluctuations, amplitude fluctuations, and criticality in extreme type-II superconductors. Phys Rev. B 60, 15307–15331 (1999).
Liang, R., Bonn, D. A. & Hardy, W. N. Discontinuities of reversible magnetization in untwinned YBCO single crystals at the first order vortex melting transition. Phys. Rev. Lett. 76, 835–838 (1996).
Fendrich, J. A. et al. Static and dynamic vortex phases in YBa2Cu3O7-δ. Phys. Rev. Lett. 77, 2073–2076 (1996).
Schilling, A. et al. Calorimetric measurement of the latent heat of vortex-lattice melting in untwinned YBa2Cu3O7-δ. Nature 382, 791–793 (1996).
Fisher, D. S., Fisher, M. P. A. & Huse, D. A. Thermal fluctuations, quenched disorder, phase transitions and transport in type-II superconductors. Phys. Rev. B 43, 130–159 (1991).
Giamarchi, T. & Le Doussal, P. Phase diagrams of flux lattices with disorder. Phys. Rev. B 55, 6577–6583 (1997).
Zeldov, E. et al. Thermodynamic observation of first-order vortex-lattice melting transition in Bi2Sr2CaCu2O8. Nature 375, 373–376 (1995).
Khaykovich, B. et al. Vortex-lattice phase transitions in Bi2Sr2CaCu2O8 crystals with different oxygen stoichiometry. Phys. Rev. Lett. 76, 2555–2558 (1996).
Cubitt, R. et al. Direct observation of magnetic flux lattice melting and decomposition in the high-Tc superconductor Bi2.15Sr1.95CaCu2O8+x. Nature 365, 407–411 (1993).
Deligiannis, K. et al. New features in the vortex phase diagram of YBa2Ca3O7-δ. Phys. Rev. Lett. 79, 2121–2124 (1997).
Sullivan, P. F. & Seidel, G. Steady-state, ac-temperature calorimetry. Phys. Rev. 173, 679–685 (1968).
Reichhardt, C., van Otterlo, A. & Zimányi, G. T. Vortices freeze like window glass: the vortex molasses scenario. Phys. Rev. Lett. 84, 1994–1997 (2000).
Williams, G. A. Vortex-loop phase transitions in liquid helium, cosmic strings, and high-Tc superconductors. Phys. Rev. Lett. 82, 1201–1204 (1999).
Onsager, L. Statistical hydrodynamics. Nuovo Cimento Suppl. 6, 279–287 (1949).
Acknowledgements
The measurements above 18 T were performed in the Grenoble High Magnetic Field Laboratory. Work at Argonne and Berkeley was supported by the US DOE.
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Bouquet, F., Marcenat, C., Steep, E. et al. An unusual phase transition to a second liquid vortex phase in the superconductor YBa2Cu3O7. Nature 411, 448–451 (2001). https://doi.org/10.1038/35078016
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DOI: https://doi.org/10.1038/35078016
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