Magnetic penetration depth in single-crystalYBa2Cu3O7−δ

Abstract

We report the first measurement of the magnetic penetration depth $\lambda (T, \theta )$ in single crystals of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ ($\delta \sim 0.1$). Results are consistent with conventional $s$-wave pairing, and yield penetration depths of ${\lambda }_{\mathrm{ab}}\mathrm{}\left(0\right)=1415\mathrm{}\pm 30$ Å and ${\lambda }_c\mathrm{}\left(0\right)>7000\mathrm{}$ Å, parallel and perpendicular to the basal plane, respectively. Comparative data on sintered Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ are also shown to be consistent with the single-crystal results. The muon-spin-rotation data, together with specific-heat results, indicate a two-dimensional carrier density of ${\eta }_{2\mathrm{D}}\approx 8\times {10}^{14}$ carriers ${\mathrm{cm}}^{-2\mathrm{}}$ and a basal-plane effective mass of $\frac{m_{\mathrm{ab}}^{*}}{m_e}\approx 10$.