Study of in-plane electrical transport anisotropy of a -axis oriented YBa2Cu3O7−δ nanodevices

In the present work, we report the growth of fully untwinned high-quality $a$-axis-oriented ${\mathrm{YBa}}₂{\mathrm{Cu}}₃{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ films on (100) ${\mathrm{SrLaGaO}}₄$ substrates by using ${\mathrm{PrBa}}₂{\mathrm{Cu}}₃{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ as a buffer layer. We also fabricated nanowires at different angles $\ensuremath{\gamma}$ with respect to the [0,1,0] direction of the substrate and studied the in-plane anisotropy of the critical current density, which we explained by considering the anisotropy in the coherence length $\ensuremath{\xi}$ and London penetration depth ${\ensuremath{\lambda}}_L$. Finally, half-integer Shapiro-like steps measured in slightly underdoped $c$-axis oriented ($\ensuremath{\gamma}={90}^{\ensuremath{\circ}}$) nanowires point towards a different transport regime, which could shed light on intriguing issues of high-critical-temperature superconductors.