Specific-Heat Measurement of Residual Superconductivity in the Normal State of Underdoped Cuprate Superconductors

Abstract

We have measured the magnetic field and temperature dependence of specific heat on $B{i}_{2}S{r}_{2-x}L{a}_{x}Cu{O}_{6+\delta }$ single crystals in wide doping and temperature regions. The superconductivity related specific heat coefficient ${\gamma }_{sc}$ and entropy $S_{sc}$ are determined. It is found that ${\gamma }_{sc}$ has a hump-like anomaly at $T_c$ and behaves as a long tail which persists far into the normal state for the underdoped samples, but for the heavily overdoped samples the anomaly ends sharply just near $T_c$. Interestingly, we found that the entropy associated with superconductivity is roughly conserved when and only the long tail part in the normal state is taken into account for the underdoped samples, indicating the residual superconductivity above T${}_c$.

4 pages, 4 figures, Accepted for publication in Physical Review Letters

References in corpus (5)

• Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor
• Visualizing pair formation on the atomic scale in the high-Tc superconductor Bi2Sr2CaCu2O8+d
• Protected nodes and the collapse of the Fermi arcs in high Tc cuprates
• Growth and post-annealing studies of La-Bi2201 single crystals
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