Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 84: Focus Session: Nanoscopic Superconducting Heterostructures
TT 84.8: Vortrag
Donnerstag, 19. März 2015, 12:45–13:00, H 0104
Correlation of 0-π transition with density of states measurements — •Ondrej Vavra1,2, Petra Högl3, Jaroslav Fabian3, Hermann Kohlstedt2, and Christoph Strunk1 — 1Inst. for Experimental and Applied Physics, University of Regensburg, Germany — 2Nanoelektronik, Technical Faculty, University of Kiel, Germany — 3Inst. for Theoretical Physics, University of Regensburg, Germany
We report on the proximity induced superconductivity in hybrid SFIFS (Nb-Fe-Al2O3-Fe-Nb) and SIFS (Nb-Al2O3-Fe-Nb) Josephson junctions. Differential conductance curves dI/dV(V) were recorded with the lock-in technique on the SFIFS samples exposed to a small magnetic field that suppresses the critical current IC. The dI/dV(V) curves reveal a peak at a voltage 2.26 mV which is attributed to the sum of the gaps of individual Nb electrodes (2ΔNb). Upon increasing iron thickness dFe a second peak develops at a voltage 1.3 mV which we attribute to the induced superconductivity in the Fe-layers. The peak height difference |GNb−GFe|(dFe) oscillates with zero crossings at 2.3 and 2.9 nm, respectively. Qualitatively, the Fe thickness dependence of dI/dV(V) behavior is the same for both SFIFS and SIFS junctions, respectively. The shape of the |GNb−GFe|(dFe) curve with its oscillations is similar to the IC(dFe) curves for Josephson junctions with F-interlayer and to the TC(dFe) dependencies for the S-F multilayers. These oscillations are observed due to the phase transition from 0 to π and vice-versa. We will discuss the results of deconvolution of dI/dV(V) curves and correlate these data with Fe thickness development of the critical current.