Possible weakly first-order superconducting transition induced by magnetic excitations in the YBCO system: A fluctuation conductivity study
Abstract
Fluctuation conductivity is experimentally studied in the genuine critical region near the superconducting transition of YBa2Cu3O7 - δ, YBa2Cu2.985Fe0.015O7 - δ and Y0.95Ca0.05Ba2Cu3O7 - δ single crystal samples. Two fluctuation regimes where the electrical conductivity diverges as a power-law of the reduced temperature were systematically observed. In the first regime, farther from the critical temperature Tc, the transition behaves as predicted by the thermodynamics of the three dimensional-XY (3D-XY) universality class characteristic of a second-order phase transition. In the asymptotic regime closer to Tc a power-law regime characterized by a much smaller exponent is observed. The smallest value ever reported for the fluctuation conductivity exponent in the high-Tc superconductors is obtained for the Fe- and Ca-doped systems. We suggest that the regime beyond 3D-XY is a crossover towards a weakly first-order transition induced by internal magnetic excitations.
- Publication:
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Physics Letters A
- Pub Date:
- April 2017
- DOI:
- 10.1016/j.physleta.2017.02.001
- Bibcode:
- 2017PhLA..381.1255H
- Keywords:
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- Y-based cuprates;
- Critical phenomena;
- Fluctuation effect;
- Effects of impurities;
- Electrical resistivity;
- Superconductivity