Kondo effect in Quantum dots / Carbon nanotubes - PowerPoint PPT Presentation

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Kondo effect in Quantum dots / Carbon nanotubes

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L. Kouwenhoven, L. Glazman. ' Revival of the Kondo effect'. Physics World, 1, 33 (2001) ... Bubbles for even-N at B=0, yet ridges can be formed at certain field ... – PowerPoint PPT presentation

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Title: Kondo effect in Quantum dots / Carbon nanotubes


1
Kondo effect in Quantum dots / Carbon nanotubes
  • Journal Club 2008/05/20
  • Fan Wu

2
Kondo effect
L. Kouwenhoven, L. Glazman. Revival of the Kondo
effect. Physics World, 1, 33 (2001)
odd e in QD
magnetic impurities
normal metal
SC
even e in QD
even
odd
3
s 0.22 for spin-half system
Nature 408, 342 (2000)
4
  • SWNT with gold leads
  • Kondo ridge for odd-N at B0
  • Bubbles for even-N at B0, yet ridges can be
    formed at certain field BC, which related with
    ground state (singlet S0) - lowest excited state
    (triplet S1) energy gap Dt-s as

M. Pustilnik, et al., Quantumdots with even
number of electrons Kondo effect in a finite
magnetic field. Phys. Rev. Lett. 84, 1756 (2000).
5
  • 12nm gold bridge on Al/Al2O3
  • Electromigration forms grain quantum dot,
    with/without submonolayer of cobalt
  • Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction
    introduce split zero-bias peak (SZBP)

6
  • Competition between the Kondo effect (energy
    scale TK) and the RKKY coupling of the spin
    (interaction strength I)

7
Nature 434, 484 (2005)
8
  • Ti/Au electrodes with CVD grown SWNT
  • dB orbital Kondo effect induced by anticrossing
    band
  • Unusually high TK 7.7K, ascribed to the
    enhanced degeneracy (one electron SU(4) and
    two-electron singlettriplet Kondo

B1.5T
9
(No Transcript)
10
  • Cr/Au electrodes with CVD grown SWNT

Ng 1, 3
SU(2)
Ng 2
11
  • InAs quantum dots with Ti/Al electrodes
  • Competition between Kondo and SC DltltkBT, Kondo
    survive with SC leads DgtgtkBT, Coulomb blockade

12
TK TK/(21/s-1)1/2, G(TK) G0/2, s0.22 for
spin-half system
13
  • Cr/Au electrodes with CVD grown SWNT

14
Coulomb energy U 2.9 meV,orbital splitting
0.7 meV, single-particle level spacing DE 3.5
meV.
  • Inelastic cotunneling with second-order
    perturbation
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