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Andreev billiards

Published on 13 December 2018

We investigated the LDOS of artificially fabricated normal metal nano-structures (Au) in contact with a superconductor (Nb). Local spectroscopic measurements revealed the presence of well defined sub-gap peaks at various positions of the STM tip. The peak features suggest they originate from quasi-particle bound states within the normal-metal structures (De Gennes St James states). Refocusing of electronic trajectories induced by the granular structure of the samples can explain the observation of spatially uncorrelated interference effects in a non-ballistic medium.

Scanning electron microscope image of an array of circular Andreev billiards (Au, diameter 200 nm surrounded by Nb).
Localized bound states in the LDOS of a square Andreev billiard measured at 60 mK for different positions of the STM tip.

Escoffier W, Chapelier C and Lefloch F
Ballistic effects in a proximity induced superconducting diffusive metal.
Physical Review B, 2005, 72(14): 140502(R)