Thermal transport in mesoscopic hybrid nanostructures: application to refrigeration

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Thermal transport in mesoscopic hybrid
nanostructures application to refrigeration
Francesco Giazotto NEST CNR-INFM and Scuola
Normale Superiore Pisa, ITALY
Physique Quantique Mésoscopique
Aussois, France, 19-22 March 2007
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Collaboration
F. Taddei, C. Castellana S. Tirelli C. Pascual
Garcia R. Fazio F. Beltram NEST CNR-INFM and
Scuola Normale Superiore, Pisa, Italy M.
Governale Institut für Theoretische Physik III,
Bochum, Germany F. W. J. Hekking CNRS
Université Joseph Fourier, Grenoble, France J.
P. Pekola O.-P. Saira T. T. Heikkilä N. Kopnin M.
Meschke A. M. Savin Helsinki University of
Technology, HUT, Helsinki, Finland
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Outline

• Part I Heat transport superconducting tunnel
  nanostructures
• NIS tunnel junctions
• Electron cooling
• Lattice cooling
• SIS and SmS junctions

• Part II Heat transport with ferromagnets and
  magnetic barriers
• FS junctions operation principle performance
• 2DEG-S systems with localized magnetic fields

• Part III Heat transport in 2DEG-N systems in
  quantizing magnetic fields
• Operation principle performance
• Electron refrigeration in 2DEG systems

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Electronic microrefrigeration motivations

• On-chip cooling (e.g., detectors, transistors)
• Realization of solid state refrigerators
• (from room temperature to millikelvin range)
• Possibility to reach very low (electron)
  temperatures by direct electronic refrigeration
  (eventually in the micro-K range)
• Control of electron distribution leads to new
  effects and devices (e.g., superconducting
  transistor, spin sources, magnetization control)

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SIN electron coolers operation principle
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SIN electron coolers electric behavior
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Injection vs relaxation
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Energy relaxation in metals
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SINIS electron coolers performance
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SINIS metallic electron coolers fabrication

• Angle SME
• Al Thermal oxidation
• Al and/or Ti (S leads)
• Cu, Ag, AlMn (N region)

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SINIS refrigerators
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Electron cooling with SIS SmS refrigerators
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Lattice cooling with NIS refrigerators
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Electron cooling in FS junction
FG et al., APL 80, 3784 (2002)
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FS cooler performance I
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Electric transport in SN contacts
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Generation of localized magnetic fields
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Electric transport through localized fields
experiments
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Superconductor-2DEG junction with a localized
magnetic field
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Differential conductance

• Different regimes
• transparent junction
• tunnel-like junction

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Differential conductance
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Requirements and applications
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Heat transport in the presence of localized
magnetic fields
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Performance
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Electronic refrigeration model
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Electronic refrigeration performance
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Landau cooling in 2DEG-N nanostructures
F.G. et al., cond-mat/0703119 (2007)
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Landau cooling I
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Landau cooling II
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Landau cooling electron refrigeration
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Summary
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Landau cooling III
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SINIS-controlled Josephson weak links
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Presence of inelastic scattering
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SINIS quasiparticle distribution function
No inelastic scattering
BCS DOS
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Transport regimes
Strong e-ph interaction (Tgt10K) local potential.
Strong e-e interaction effective T(x)
(hot-electron regime)
Only elastic scattering double-step distribution
(mesoscopic regime)
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Normal metal control line quasiparticle
distribution
VC
Nr
V Vc/2
L
Nl
V -Vc/2
eVc
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SER performance
J. Pekola, FG, and O.P. Saira, Phys. Rev Lett.
98, 037201 (2007)
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Membranes cooling
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Proximity effect and supercurrent
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Heat transistor
O.P. Saira et al., cond-mat/0702361
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FS cooler performance II
COP ?out / ?in
COP 23
Al/CrO2 (half-metallic ferromagnet)
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Radio-frequency single-electron refrigerator (SER)
J. Pekola, FG, and O.P. Saira, Phys. Rev Lett.
98, 037201 (2007)