Nanoscale physics

Microware properties of Josephson junctions embedded in a MoxRe1-x surface electromagnetic wave resonator
Rudenko E.M.1, Korotash I.V.1, Krakovny A.O.1, Polotskiy D. Yu.1, Malyshev V.Yu.2, Prokopenko O.V.2
1 G.V. Kurdyumov Institute for Metal Physics, N.A.S. of Ukraine, Boulevard of Academician Vernadsky, 36, Kyiv-03142, Ukraine. 
E-mail: metall@imp.kiev.ua 
2 Taras Shevchenko National University of Kyiv, Volodymyrska street, 64/13, Kyiv-01601, Ukraine

Surface electromagnetic waves (SEWs) are well-known in modern optics, microwave and terahertz-frequency electronics and widely used due to their unique electrodynamic properties, for instance strong interaction of SEW with conducting surfaces like superconducting films. This interaction is especially strong in resonance systems, which makes the surface electromagnetic wave resonator (SEWR) to be a convenient instrument for the study of microwave properties of promising superconductors like MoxRe1-x.
In this work we study microwave properties of PbSn-I-Pb Josephson junctions (JJ) embedded in the Mo0.55Re0,45 SEWR. The resonator’s Mo0.55Re0,45 film of the thickness 200 nm was deposited on a sapphire dielectric substrate with sizes 10×8×0.5 mm by a dc magnetron sputtering. Above the film a 100 nm-thick AlN layer was deposited and then PbSn-I-Pb junctions were created.
Current-voltage characteristic (CVC) of JJs, measured by a four-probe method at the temperature of 4.2 K, indicated that the behavior of studied JJs was similar to the behavior of a tunnel junction. Also a strong modulation of the Josephson current by a dc magnetic field was observed (CVC was similar to the “Fraunhofer” one). The obtained dependence of the critical current for all three used JJs on the frequency (8.5–10.3 GHz) and power (~1 mW and less) of an external microwave signal shows that PbSn-I-Pb junction on a pure sapphire substrate (without SEWR) had dramatically responded to a 9 GHz microwave signal (the reduction of the critical current at this frequency was about 60%). However, for a sample with SEWR (with bi-layer structure MoRe/AlN) only small fluctuations of the Josephson critical current at this frequency were observed. Meanwhile at the frequency of 8,985 GHz voltage steps of the 20 μV widths on the CVC were observed, which then were disappeared at the frequency of 9,157 GHz. Thus, it has been found that the film SEWR structure with embedded JJs was suitable for the quasi-resonance detection of microwave signals.