Enhancement of Kondo Effect in Multilevel Quantum Dots

2004/08/07 by Mikio Eto
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Semiconductor Quantum Structures and Devices #cond-mat.mes-hall

paper · pdf · doi:10.1143/jpsj.74.95

15 pages, 6 figures

arxiv created 2004/08/07 · openalex publication_date 2005/01/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

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.

Citations

• Transport in Multilevel Quantum Dots: From the Kondo Effect to the Coulomb Blockade Regime
• Low Temperature Transport through a Quantum Dot: The Anderson Model out of Equilibrium
• Quantum Dots with Even Number of Electrons: Kondo Effect in a Finite Magnetic Field
• Singlet Ground State of the Localizedd-Electrons Coupled with Conduction Electrons in Metals
• Quantum Phase Transition in a Multilevel Dot
• Theory of the atomic limit of the Anderson model. I. Perturbation expansions re-examined
• Resistance Minimum in Dilute Magnetic Alloys