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Enhancement of Kondo effect in multilevel quantum dots

Mikio Eto
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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 Δis 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.

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Mikio Eto. 2004-08-07. Enhancement of Kondo effect in multilevel quantum dots. https://doi.org/10.1143/jpsj.74.95

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