### 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 language | English |
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Pages (from-to) | 95-102 |

Number of pages | 8 |

Journal | Journal of the Physical Society of Japan |

Volume | 74 |

Issue number | 1 |

DOIs | |

Publication status | Published - 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)