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Superconducting parity effect across the Anderson limit
#MMPMID28240294
Vlaic S
; Pons S
; Zhang T
; Assouline A
; Zimmers A
; David C
; Rodary G
; Girard JC
; Roditchev D
; Aubin H
Nat Commun
2017[Feb]; 8
(?): 14549
PMID28240294
show ga
How small can superconductors be? For isolated nanoparticles subject to quantum
size effects, P.W. Anderson in 1959 conjectured that superconductivity could only
exist when the electronic level spacing ? is smaller than the superconducting gap
energy ?. Here we report a scanning tunnelling spectroscopy study of
superconducting lead (Pb) nanocrystals grown on the (110) surface of InAs. We
find that for nanocrystals of lateral size smaller than the Fermi wavelength of
the 2D electron gas at the surface of InAs, the electronic transmission of the
interface is weak; this leads to Coulomb blockade and enables the extraction of
electron addition energy of the nanocrystals. For large nanocrystals, the
addition energy displays superconducting parity effect, a direct consequence of
Cooper pairing. Studying this parity effect as a function of nanocrystal volume,
we find the suppression of Cooper pairing when the mean electronic level spacing
overcomes the superconducting gap energy, thus demonstrating unambiguously the
validity of the Anderson criterion.
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