Counter intuitive consequence of heating in strongly-driven intrinsic-junctions of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} mesas.
Anomalously high and sharp peaks in the conductance of intrinsic Josephson junctions in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi2212) mesas have been commonly interpreted as superconducting energy gaps but here we show they are a result of strong self-heating. This conclusion follows directly from a comparison to the equilibrium gap measured by tunneling in single break junctions on equivalent crystals. As the number of junctions in the mesa, N, and thus heating increase, the peak voltages decrease and the peak width abruptly sharpens for N {ge} 12. Clearly these widely variable features vs N cannot all represent the equilibrium properties. Our data imply that the sharp peaks represent a transition to the normal state. That it occurs at the same dissipated power for N = 12-30 strongly implicates heating as the cause. Although peak sharpening due to heating is counterintuitive, as tunneling spectra usually broaden at higher temperatures, a lateral temperature gradient, leading to coexistence of normal hot spots and superconductive regions, qualitatively explains the behavior. However, a more uniform temperature profile cannot be ruled out. As the peak's width and voltage in our shortest mesa (N = 6) are more consistent with the break junction data, we propose a figure of merit for Bi2212 mesas, the relative conductance peak width, such that small values signal a crossover into the strong self-heating regime.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; Scientific and Technical Research Council of Turkey; Turkey Academy of Sciences
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 983471
- Report Number(s):
- ANL/MSD/JA-67227
- Journal Information:
- Phys. Rev. B, Journal Name: Phys. Rev. B Journal Issue: 2010 Vol. 81; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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