Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 66: Superconductivity: Tunneling, Josephson Junctions, SQUIDs

TT 66.11: Vortrag

Mittwoch, 18. März 2015, 18:00–18:15, H 2053

Dynamics of a nanoscale Josephson junction probed by scanning tunneling microscopy — •Christian R. Ast¹, Berthold Jäck¹, Matthias Eltschka¹, Markus Etzkorn¹, and Klaus Kern^1,2 — ¹Max-Planck-Institut für Festkörperforschung, Stuttgart — ²Institut de Physique de la Matière Condensée, EPFL, Lausanne

The Josephson effect is an intriguing phenomenon as it presents an interplay of different energy scales, such as the Josephson energy є_J (critical current), charging energy є_C, and temperature T. Using a scanning tunneling microscope (STM) operating at a base temperature of 15 mK, we create a nanoscale superconductor-vacuum-superconductor tunnel junction in an extremely underdamped regime (Q≫10). We observe extremely small retrapping currents also owing to strongly reduced ohmic losses in the well-developed superconducting gaps. While formally operating in the zero temperature limit, i. e. the temperature T is smaller than the Josephson plasma frequency ω_J (k_BT≪ℏω_J=√8є_Jє_C), experimentally other phenomena, such as stray photons, may perturb the Josephson junction, leading to an effectively higher temperature. The dynamics of the Josephson junction can be addressed experimentally by looking at characteristic parameters, such as the switching current and the retrapping current. We discuss the dynamics of the Josephson junction in the context of reaching the zero temperature limit.