Description:

Development of a nanometer-scale magnetic sensing technique applicable to individual magnetic particles enables revolutionary progress in physical, biological and medical sciences. The drive towards this new scale requires reduction in size of SQUIDs (superconducting quantum interference devices, currently the most sensitive magnetometers used in practice) in order to perform sensitive detection of very weak magnetic fields below the length of 100 nm, the conventional definition of the nanoscale. As well known, SQUIDs are based on superconducting loops containing Josephson junctions. Unfortunately, at the nanoscale the SQUID loop may not satisfy the assumption to be thicker than the penetration depth and possible solution could be to transfer from nanoSQUIDs to nanoscale Josephson junctions. Proof-of-principle experiments implemented at the Northwestern University have revealed SQUID-like oscillatory behavior with magnetic field in a singly connected Josephson junction involving a comparatively thick and strongly anisotropic (Al/Ni)10Al barrier enclosed between two Nb electrodes. Accompanying model calculations suggest the effect arises from Andreev bound states localized at the barrier edges that dominate the contributions from its disordered interior. Some other advantages of the novel Josephson devices important for practical applications are discussed as well.

Professor Mikhail Belogolovskii, G.V. Kurdyumov Institute for Metal Physics, Kyiv

Host: John Ketterson

Keywords: Physics, Astronomy, Condensed Matter