An excursion into modern superconductivity: from nanoscience to cold atoms and holography Yuzbashyan Rutgers Altshuler Columbia Urbina Regensburg Richter Regensbur g Sangita Bose, Tata, Max Planck Stuttgart Kern Stuttgart Diego Rodriguez Queen Mary Sebastian Franco Santa Barbara Masaki Tezuka Kyoto Jiao Wang NUS Antonio M. García-García
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An excursion into modern superconductivity: from nanoscience to cold atoms and holography Yuzbashyan Rutgers Altshuler Columbia Urbina Regensburg Richter.
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An excursion into modern superconductivity: from
nanoscience to cold atoms and holography
Yuzbashyan Rutgers
Altshuler Columbia
Urbina Regensburg
Richter Regensburg
Sangita Bose, Tata, Max Planck Stuttgart
Kern Stuttgart
Diego Rodriguez Queen Mary
Sebastian Franco Santa Barbara
Masaki Tezuka Kyoto
Jiao Wang NUS
Antonio M. García-García
Superconductivity in nanograins
New forms of superconductivity
New tools String Theory
Increasing the superconductor
Tc
Superconductivity
Practical
Technical
Theoretical
Enhancement and control of superconductivity in nanograins
Phys. Rev. Lett. 100, 187001 (2008)
Yuzbashyan Rutgers
Altshuler Columbia
Urbina Regensburg
Richter Regensburg
Sangita Bose, Tata, Max Planck Stuttgart
Kern Ugeda, Brihuega
arXiv:0911.1559
Nature Materials
L
1. Analytical description of a clean, finite-size BCS superconductor?
2. Are these results applicable to realistic grains?
Main goals
3. Is it possible to increase the critical temperature?
The problem
Semiclassical 1/kF L <<1 Berry, Gutzwiller, Balian
Can I combine this?
Is it already done?
BCS gap equation
?V finite
Δ=?
V bulk Δ~
De-1/
Relevant Scales
Mean level spacing
Δ0 Superconducting gap
F Fermi Energy
L typical length
l coherence length
ξ Superconducting coherence length
Conditions
BCS / Δ0 << 1
Semiclassical1/kFL << 1
Quantum coherence l >> L ξ >> L
For Al the optimal region is L ~ 10nm
Go ahead! This has not been done before
Maybe it is possible
It is possible but, is it relevant?
If so, in what range of parameters?
Corrections to BCS
smaller or larger?
Let’s think about this
A little history
Parmenter, Blatt, Thompson (60’s) : BCS in a rectangular grain
Heiselberg (2002): BCS in harmonic potentials, cold atom appl.
Shanenko, Croitoru (2006): BCS in a wire
Devreese (2006): Richardson equations in a box
Kresin, Boyaci, Ovchinnikov (2007) Spherical grain, high Tc
Olofsson (2008): Estimation of fluctuations in BCS, no correlations
Superconductivity in particular geometries
Nature of superconductivity (?) in ultrasmall systems
Breaking of superconductivity for / Δ0 > 1? Anderson (1959)
Experiments Tinkham et al. (1995) . Guo et al., Science 306, 1915, Superconductivity Modulated by quantum Size Effects.
Even for / Δ0 ~ 1 there is “supercondutivity
T = 0 and / Δ0 > 1 (1995-)
Richardson, von Delft, Braun, Larkin, Sierra, Dukelsky, Yuzbashyan