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

Abstract

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 $d_{x^2-y^2}+is$ or $d_{x^2-y^2}+i{d}_{xy}$. We find that a surface-induced $d_{x^2-y^2}+is$ phase creates a global spectroscopic gap which increases with applied magnetic field, consistent with experimental observation.

5 pages, three figures, accepted for publication in Physical Review Letters

References in corpus (3)

• Edge properties of the chiral d-wave superconducting state in doped graphene
• Search for broken time-reversal symmetry near the surface of YBCO films using Beta-NMR
• Transition from a mixed to a pure d-wave symmetry in superconducting optimally doped YBa${}_2$Cu${}_3$O${}_{7-x}$ thin films under applied fields

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