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TU Dresden » Faculty of Mechanical Science and Engineering » Institute for Materials Science » Chair of Materials Science and Nanotechnology

Wednesday, 07 July 2004
(at 10:15 in room Phy 4.1.13)
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Quantum dots and the Kondo effect (1/3):
Coherent transport in quantum dots (general overview)

Kicheon Kang

Department of Physics
Chonnam National University
  South Korea  

The main goal of the seminar series is to discuss the Kondo effect that appears in various quantum dot devices. The Kondo effect takes place when there are spin exchange interactions between a local magnetic moment and conduction electrons. In mesoscopic systems such as quantum dots, parameters characterizing the Kondo effect can be controlled, so that "tunable" Kondo effect has been reallized experimentally.
First, I will provide general overview on the coherent transport in quantum dots. After brief introduction of basic concepts of mesoscopic physics, the role of phase-coherent transport through quantum dots will be discussed in relation to recent experimental and theoretical works.
In the second seminar, I will discuss the Kondo effect in quantum dots. Especially I will focus on the fact that the Kondo scattering is a phase-coherent process. By considering a model that includes nonresonant transmission as well as the Anderson impurity, we explain unusually large phase evolution of about in the Kondo valley observed in recent experiments. We argue that this anomalous phase evolution is a universal property that can be found in the high-temperature Kondo phase in the presence of the time-reversal symmetry.
The last seminar will be devoted to the following question: What will happen to the "Kondo effect" if the size of the "metalic" host itself is mesoscopic? The physics of this "mesoscopic Kondo system" is characterized by the ratio of the energy level spacing of the host to the Kondo temperature TK, or equivalently, by the relative size of the ring and the Kondo screening cloud. To investigate this fundamental question we consider a system of an interacting quantum dot tunnel-coupled to a mesoscopic Aharonov-Bohm (AB) ring. The mesoscopic Kondo effect is investigated in two different ways: (i) Persistent Current (PC), and (ii) Transport Spectroscopy. It is shown that the Kondo effect depends on the phase of hopping amplitude between the quantum dot and the ring while its magnitude remains unchanged.
Related articles

  1. J. Kim et al., "Fano Resonance in Crossed Carbon Nanotubes", Phys. Rev. Lett. 90, 166403 (2003).
  2. K. Kang et al., "Anomalous Transmission Phase of a Kondo-Correlated Quantum Dot", cond-mat/0401169.
  3. K. Kang, et al., "Anti-Kondo resonance in transport through a quantum wire coupled to a quantum dot", Phys. Rev. B 63, 113304 (2001).
  4. K. Kang, and S.-C. Shin, "Mesoscopic Kondo Effect in an Aharonov-Bohm Ring", Phys. Rev. Lett. 85, 5619 (2000).
  5. S. Y. Cho et al., "Spin Fluctuation and Persistent Current in a Mesoscopic Ring Coupled to a Quantum Dot", Phys. Rev. B 64, 033314 (2001).
  6. K. Kang et al., "Spin-Fluctuation-Induced Dephasing in a Mesoscopic Ring", Phys. Rev. B 66, 075312 (2002).
  7. K. Kang and L. Craco, "Mesoscopic Kondo Resonance in a Quantum Dot Connected to an Aharonov-Bohm Ring", Phys. Rev. B 65, 033302 (2002).

slides (pdf)

Invited by G. Cuniberti (MC seminar)

Within the Vielberth Foundation visiting program

last modified: 2021.10.21 Thu
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