Experimental survey of critical fluctuations in the specific heat of high-temperature superconductors |
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Authors: | Alain Junod Marlyse Roulin Bernard Revaz and Andreas Erb |
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Institution: | Département de Physique de la Matière Condensée, Université de Genève, 24, quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland |
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Abstract: | Thermal fluctuations are observed in the specific heat of high-temperature superconductors (HTS) near Tc. This is seen both in the shape of the zero-field anomaly, characterized by critical exponents and amplitude ratios, and in the broadening of the transition versus the magnetic field, which obeys scaling laws. 3D-XY fluctuations are found for YBa2Cu3Ox (Y-123) near optimal doping, whereas systematic deviations occur away from this point. The large deviations found for the most anisotropic HTS may be attributed to both reduced dimensionality and a crossover between BCS and Bose condensations. Low-temperature data are discussed in this context. The melting curve of vortex matter, now detected in the specific heat of Dy-123, Eu-123 and Y-123 up to very high fields, is described by a critical exponent. |
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Keywords: | High-temperature superconductors Specific heat at Tc Critical behavior Bose–Einstein condensation |
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