Enhancement of Kondo effect in multilevel quantum dots

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Abstract

We theoretically study enhancement mechanisms of the Kondo effect in multilevel quantum dots. In quantum dots fabricated on semiconductors, the energy difference between discrete levels Δ is tunable by applying a magnetic field. With two orbitals and spin 1/2 in the quantum dots, we evaluate the Kondo temperature T K as a function of Δ, using the scaling method. T K is maximal around Δ = 0 and decreases with increasing |Δ|, following a power law, T K(Δ) = T K(0)·(T K(0)/|Δ|) γ, which is understood as a crossover from SU(4) to SU(2) Kondo effect. The exponents on both sides of a level crossing, γ L and γ R, satisfy a relation of γ L·γ R = 1. We compare this enhanced Kondo effect with that by spin-singlet-triplet degeneracy for an even number of electrons, to explain recent experimental results using vertical quantum dots.

Original languageEnglish
Pages (from-to)95-102
Number of pages8
JournalJournal of the Physical Society of Japan
Volume74
Issue number1
DOIs
Publication statusPublished - 2005 Jan 1

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Keywords

  • Kondo effect
  • Multilevel
  • Quantum dot
  • SU(4) Kondo effect
  • Scaling method

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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