1304.4054 (Annica M. Black-Schaffer et al.)

Model evidence of a superconducting state with a full energy gap in
small cuprate islands    [PDF]

Annica M. Black-Schaffer, Dmitri S. Golubev, Thilo Bauch, Floriana Lombardi, Mikael Fogelström

We investigate subdominant order parameters stabilizing at low temperatures in nano-scale high-T$_c$ cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa$_2$Cu$_3$O$_{7-\delta}$ [D. Gustafsson {\it et al}, Nature Nanotech. {\bf 8}, 25 (2013)]. Using complementary quasi-classical and tight-binding Bogoliubov-de Gennes methods, we show on distinctly different properties dependent on the symmetry being $d_{x^2-y^2}+i s$ or $d_{x^2-y^2}+i d_{xy}$. We find that a surface-induced $d_{x^2-y^2}+i s$ phase creates a global spectroscopic gap which increases with applied magnetic field, consistent with experimental observation.

View original: http://arxiv.org/abs/1304.4054