### 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 |

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### Keywords

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

### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

**Enhancement of Kondo effect in multilevel quantum dots.** / Eto, Mikio.

Research output: Contribution to journal › Article

*Journal of the Physical Society of Japan*, vol. 74, no. 1, pp. 95-102. https://doi.org/10.1143/JPSJ.74.95

}

TY - JOUR

T1 - Enhancement of Kondo effect in multilevel quantum dots

AU - Eto, Mikio

PY - 2005/1

Y1 - 2005/1

N2 - 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.

AB - 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.

KW - Kondo effect

KW - Multilevel

KW - Quantum dot

KW - Scaling method

KW - SU(4) Kondo effect

UR - http://www.scopus.com/inward/record.url?scp=24744456660&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=24744456660&partnerID=8YFLogxK

U2 - 10.1143/JPSJ.74.95

DO - 10.1143/JPSJ.74.95

M3 - Article

AN - SCOPUS:24744456660

VL - 74

SP - 95

EP - 102

JO - Journal of the Physical Society of Japan

JF - Journal of the Physical Society of Japan

SN - 0031-9015

IS - 1

ER -