Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation

Superconducting nanoribbon with a constriction: A quantum-confined Josephson junction

“…Nanoscale superconductivity, in which one or more dimensions are smaller than the coherence length, exhibits a range of interesting phenomena, such as Berezinskii-Kosterlitz-Thouless (BKT) phase transitions 1,2 , excess conductivity induced by superconducting fluctuations 3 , and the superconductor-insulator quantum phase transition at zero temperature 4 , to name a few. In particular, when the size of the superconductor becomes comparable to the electron Fermi wavelength λ F , the formation of discretized electronic energy levels results in the oscillations of the density of states at the Fermi level with the size, together with the reconfiguration of the pairing interaction, leading to the oscillatory behavior of superconducting critical temperature T c and other observables [5][6][7][8][9][10][11][12][13][14][15][16] , i.e. the so-called quantum size effects.…”

“…Recent progress in nanotechnology has allowed highquality superconducting nanostructures to be fabricated with atomic-scale precision 17,18 . Superconductivity is realized in atomically thin films even down to a single monolayer.…”

“…Quantum size effects have been reported in atomically thin films 19 , superconducting nanoparticles 20 and islands 21 , nanowires 22 and nanowire arrays 23 . However, the low-dimensional superconductivity is strongly influenced by the imperfections such as impurities, disorder and structural defects 24 . In nanofilms, increasing disorder results in the phase transition from a superconducting to an insulating state 4 .…”

“…However, the low-dimensional superconductivity is strongly influenced by the imperfections such as impurities, disorder and structural defects 24 . In nanofilms, increasing disorder results in the phase transition from a superconducting to an insulating state 4 . In addition, impurities locally suppress superconductivity, which in superconducting nanowires can promote a phase slip center, giving rise to the broad temperature transition and residual resistance 25,26 .…”

“…In nanofilms, increasing disorder results in the phase transition from a superconducting to an insulating state 4 . In addition, impurities locally suppress superconductivity, which in superconducting nanowires can promote a phase slip center, giving rise to the broad temperature transition and residual resistance 25,26 . Very recently, a step in atomically thin films was found to have a strong effect on electronic transport 27,28 and vortex matter 24,29,30 , as a new paradigm in the interplay between the local defects and low-dimensional superconductivity.…”