German-Ukrainian Seminar on Quantum Materials
Lecture #8: April 6 2023 at 14:00 Kyiv time (13:00 Dresden time)
Meeting ID: 992 8170 3595 // Passcode: 963908
Speaker: Mikhail Belogolovskii, Kyiv Academic University
Title: Quantum interference patterns in new types of Josephson junctions
Josephson junction formed by two superconducting films connected with a weak link, e.g., a tunnel barrier or a normal interlayer, can support a non-dissipative supercurrent driving by a phase difference between the electrodes. The introduction of magnetic fields into such devices or more complex structures based on them leads to fundamentally new phenomena. The Fraunhofer-like pattern of the maximum Josephson current in a single Josephson junction and the periodic field dependence of the critical current in a two-junction quantum interferometer (SQUID) are analogues of corresponding classical interference effects in optics (one-slit and two-slit interference patterns, respectively). In this talk, I present two new types of stacked Josephson junctions developed and studied together with US colleagues (I.P. Nevirkovets and J.B. Ketterson, Northwestern University, Evanston, IL), namely, the first Josephson device with two amorphous superconducting electrodes demonstrating ideal high-uniform tunneling characteristics and the first Josephson junction formed by ordinary metallic films that exhibits SQUID-like supercurrent-magnetic field dependencies. We believe that the former samples will avoid non-homogeneous current distributions inside a weak link, which can lead, in particular, to supercurrent behavior mimicking a so-called 0 - Pi transition. The latter devices with edge-dominated currents across a weak link are expected to be promising candidates for a new generation of magnetic field nanosensors.