Doping dependence of the upper critical field in the electron-doped cuprate superconductor PCCO via the Nernst effect

Superconducting fluctuations are known to persist above the critical temperature $T_{\rm c}$ and above the upper critical magnetic field $H_{\rm c2}$. The Nernst effect was shown to be a powerful probe of these fluctuations [1], in quantitative agreement with theory [2]. Here we report a detailed study of the Nernst effect in high-quality films [3] of the electron-doped cuprate superconductor PCCO, from which we extract $H_{\rm c2}$ as a function of doping. We find that $H_{\rm c2}$ follows the dome-like doping dependence of $T_{\rm c}$, revealing that the pairing strength decreases with underdoping, as it does in hole-doped cuprates [4].\\[4pt] [1] A. Pourret \textit{et al.}, Nat. Phys. {\bf 2}, 683 (2006)\\[0pt] [2] M. N. Serbyn \textit{et al.}, Phys. Rev. Lett. {\bf 102}, 067001 (2009); K. Michaeli and A. M. Finkel'stein, Europhys. Lett. {\bf 86}, 27007 (2009)\\[0pt] [3] G. Roberge \textit{et al.}, J. of Crystal Growth. {\bf 311}, 1340 (2009) \\[0pt] [4] J. Chang \textit{et al}., Nat. Phys. {\bf 8}, 751 (2012)