Decrease of upper critical field with underdoping in cuprate superconductors

• Published in: Nature physics Vol. 8; no. 10; pp. 751 - 756
• Main Authors: Chang, J., Doiron-Leyraud, N., Cyr-Choinière, O., Grissonnanche, G., Laliberté, F., Hassinger, E., Reid, J-Ph, Daou, R., Pyon, S., Takayama, T., Takagi, H., Taillefer, Louis
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.10.2012; Nature Publishing Group
• Subjects: 639/766/119/1003; 639/766/119/2795; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; COPPER OXIDE; Cuprates; DOPING; ELECTRICAL CONDUCTIVITY; Fluctuations; MAGNETIC FIELD; Magnetic fields; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; SUPERCONDUCTIVITY; SUPERCONDUCTORS; Temperature; Theoretical; Thermomagnetic effects; Tracking; TRANSITION TEMPERATURE; Transition temperatures; YTTRIUM OXIDE
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2380

It is still unclear why the transition temperature T c of cuprate superconductors falls with underdoping. The doping dependence of the critical magnetic field H c2 is directly relevant to this question, but different estimates of H c2 are in sharp contradiction. We resolve this contradiction by tracking the characteristic field scale of superconducting fluctuations as a function of doping, via measurements of the Nernst effect in La 1.8− x Eu 0.2 Sr x CuO 4 . H c2 is found to fall with underdoping, with a minimum where stripe order is strong. The same non-monotonic behaviour is observed in the archetypal cuprate superconductor YBa 2 Cu 3 O y . We conclude that competing states such as stripe order weaken superconductivity and cause both H c2 and T c to fall as cuprates become underdoped. Decreasing the doping of a cuprate superconductor below a certain critical value causes its critical temperature to fall, however the reason for this has been unclear. Sensitive measurements of the Nernst effect in yttrium barium copper oxide suggest it is the result of competition with an emerging stripe phase.