Regensburg 2019 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 55: Superconductivity: Tunneling and Josephson Junctions
TT 55.3: Vortrag
Donnerstag, 4. April 2019, 10:00–10:15, H23
Hysteresis in current-voltage characteristics of sub-micron Nb-HfTi-Nb SNS-type Josephson junctions — •Julian Linek1, Benedikt Müller1, Viacheslav Morosh2, Thomas Weinmann2, Oliver Kieler2, Reinhold Kleiner1, and Dieter Koelle1 — 1Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universität Tübingen, Germany — 2Fachbereich Quantenelektronik, PTB Braunschweig, Germany
SNS-type Josephson junctions (JJs) based on superconducting (S) Nb thin films with a normal metal (N) HfTi barrier offer high critical current densities up to 1 MA/cm2 with usually non-hysteretic current-voltage characteristics (IVCs) at temperature T = 4.2 K. By patterning a Nb-HfTi-Nb trilayer with e-beam lithography, highly sensitive dc SQUIDs with sub-µm lateral dimensions can be fabricated. Such nanoSQUIDs are suited for the investigation of magnetism at the nano scale. Unfavorably, hysteresis in the IVCs appears upon increasing the critical current; this prevents SQUID operation at the optimum working point and thus leads to a degradation in sensitivity. Main features of IVCs measured at variable T resemble those of constriction type JJs with thermaly induced hysteresis. We performed numerical simulations of IVCs and compared those to measurements on our SNS-JJs from 0.3 to 9 K. RSJ-based simulations include the balance of Joule heating and 1-dim. thermal heat flow to describe the increase of T in the barrier layer. Despite the simplicity of our model, major properties of the experimentally determined IVCs, such as the saturation of the return current Ir(T) at low T, can be reproduced by our simulations.