Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 62: Superconductivity: Properties, Electronic Structure, Order Parameter

TT 62.7: Talk

Thursday, March 14, 2013, 17:00–17:15, H19

Imaging the Anisotropic Nonlinear Meissner Effect in Unconventional Superconductors — Alexander P. Zhuravel¹, Behnood G. Ghamsari², Cihan Kurter², •Philipp Jung³, Stephen Remillard⁴, John Abrahams², Alexander Lukashenko³, Alexey V. Ustinov³, and Steven M. Anlage^2,3 — ¹B. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 61103 Kharkov, Ukraine — ²CNAM, Physics Department, University of Maryland, College Park, ML 20742-4111, USA — ³Physikalisches Institut and DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology, 76128 Karlsruhe, Germany — ⁴Physics Department, 27 Graves Place, Hope College, Holland, MI 49422, USA

We present measurements on the anisotropic nonlinear Meissner effect (aNLME). Using a laser scanning microscope we have directly imaged this effect in a self-resonant spiral patterned from a thin film of the d_x²−y² superconductor YBa₂Cu₃O_7−δ. The spiral is excited at one of its resonant frequencies while a focused laser spot is scanned across its surface. The local illumination by the laser gives rise to a detectable change in the resonant properties. At low temperatures, the aNLME causes a direction dependent contribution to the critical current density. This makes it possible to image the directions of nodes and anti-nodes of the superconducting order parameter and the contribution of Andreev bound states associated with them. These two contributions to the photoresponse can be distinguished by their temperature dependence, which is consistent with theoretical predictions.