29 research outputs found
Single Wall Carbon Nanotube Weak Links
We have reproducibly contacted gated single wall carbon nanotubes (SWCNT) to
superconducting leads based on niobium. The devices are identified to belong to
two transparency regimes: The Coulomb blockade and the Kondo regime. Clear
signature of the superconducting leads is observed in both regimes and in the
Kondo regime a narrow zero bias peak interpreted as a proximity induced
supercurrent persist in Coulomb blockade diamonds with Kondo resonances.Comment: Proceeding for International Symposium on Mesoscopic
Superconductivity and Spintronics 2006, NTT BRL, Atsugi, Japa
Single nanowire solar cells beyond the Shockley-Queisser limit
Light management is of great importance to photovoltaic cells, as it
determines the fraction of incident light entering the device. An optimal
pn-junction combined with an optimal light absorption can lead to a solar cell
efficiency above the Shockley-Queisser limit. Here, we show how this is
possible by studying photocurrent generation for a single core-shell p-i-n
junction GaAs nanowire solar cell grown on a silicon substrate. At one sun
illumination a short circuit current of 180 mA/cm^2 is obtained, which is more
than one order of magnitude higher than what would be predicted from
Lambert-Beer law. The enhanced light absorption is shown to be due to a light
concentrating property of the standing nanowire as shown by photocurrent maps
of the device. The results imply new limits for the maximum efficiency
obtainable with III-V based nanowire solar cells under one sun illumination.Comment: 19 pages, 3 figure
Kondo-enhanced Andreev tunneling in InAs nanowire quantum dots
We report measurements of the nonlinear conductance of InAs nanowire quantum
dots coupled to superconducting leads. We observe a clear alternation between
odd and even occupation of the dot, with sub-gap-peaks at
markedly stronger(weaker) than the quasiparticle tunneling peaks at
for odd(even) occupation. We attribute the enhanced
-peak to an interplay between Kondo-correlations and Andreev tunneling
in dots with an odd number of spins, and substantiate this interpretation by a
poor man's scaling analysis