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Statistical detection of Josephson, Andreev, and single quasiparticle currents in scanning tunneling microscopy...

by Wonhee Ko, Eugen F Dumitrescu, Petro Maksymovych
Publication Type
Journal
Journal Name
Physical Review Research
Publication Date
Page Number
033248
Volume
3
Issue
3

We present a method to identify distinct tunneling modes in a tunable superconducting tunnel junction composed of a superconducting tip and a sample in a scanning tunneling microscope. Combining the relative decay constant of tunneling current extracted from I−V−z spectroscopy with its statistical analysis over the atomic disorders in the sample surface, we identified the crossover of dominant tunneling modes between single charge tunneling, Andreev reflection (AR), and Josephson tunneling with respect to the bias voltage at a measurement temperature nearly half of the critical temperature. The method enables one to determine the specific tunneling regime independently of the spectral shapes and to reveal intrinsic modulation of AR and Josephson current by disorder that will be crucial for superconducting quantum information processing.