We report on a comprehensive study of spin-Kondo effect in a strongly-coupled quantum dot realized in a high-quality InAs nanowire. The nanowire quantum dot is relatively symmetrically coupled to its two leads, so the Kondo effect reaches the Unitary limit. The measured Kondo conductance demonstrates scaling with temperature, Zeeman magnetic field, and out-of-equilibrium bias. The suppression of the Kondo conductance with magnetic field is much stronger than would be expected based on a g-factor extracted from Zeeman splitting of the Kondo peak. This may be related to strong spin-orbit coupling in InAs.

The interaction between a single confined spin Even though recent experiments have established this system as a new paradigm for solid-state quantum optics, all of the striking experimental observations to date could be understood within the framework of single-or few-particle physics enriched by perturbative coupling to reservoirs involving either phonons, a degenerate electron gas [7,8], or nuclear spins [9,10]).We present differential transmission (DT)

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The Kondo scale T K for impurity systems is expected to guarantee universal scaling of physical quantities. However, in practice, not every definition of T K necessarily supports this notion away from the strict scaling limit. Specifically, this paper addresses the role of finite bandwidth D in the strongly correlated Kondo regime. For this, various theoretical definitions of T K are analyzed based on the inverse magnetic impurity susceptibility at zero temperature. While conventional definitions in that respect quickly fail to ensure universal Kondo scaling for a large range of D, this paper proposes an altered definition of T sc K that allows universal scaling of dynamical or thermal quantities for a given fixed Hamiltonian. If the scaling is performed with respect to an external parameter that directly enters the Hamiltonian, such as magnetic field, the corresponding T sc,B K for universal scaling differs, yet becomes equivalent to T sc K in the scaling limit. The only requirement for universal scaling in the full Kondo parameter regime with a residual error of less than 1% is a well-defined isolated Kondo feature with T K 0.01 D irrespective of specific other impurity parameter settings. By varying D over a wide range relative to the bare energies of the impurity, for example, this allows a smooth transition from the Anderson to the Kondo model.

We consider iron impurities in the noble metals gold and silver and compare experimental data for the resistivity and decoherence rate to numerical renormalization group results. By exploiting non-Abelian symmetries we show improved numerical data for both quantities as compared to previous calculations [Costi et al., Phys. Rev. Lett. 102, 056802 (2009)], using the discarded weight as criterion to reliably judge the quality of convergence of the numerical data. In addition we also carry out finite-temperature calculations for the magnetoresistivity of fully screened Kondo models with S = 1 2 , 1 and 3 2 , and compare the results with available measurements for iron in silver, finding excellent agreement between theory and experiment for the spin-3 2 three-channel Kondo model. This lends additional support to the conclusion of Costi et al. that the latter model provides a good effective description of the Kondo physics of iron impurities in gold and silver. 72.70.+m, 75.20.Hr The magnetic alloys for which the Kondo effect was first observed, in the 1930s, were iron impurities in gold and silver 1,2 . They showed an anomalous rise in the resistivity with decreasing temperature, which Kondo explained in 1964 as being due to an antiferromagnetic exchange coupling between the localized magnetic impurity spins and the spins of the delocalized conduction electrons 3 . For his work, Kondo used a spin-1 2 , one-band model, which undoubtedly captures the essential physics correctly in a qualitative way.However, detailed comparisons between theory and experiment have since shown that this model does not yield a quantitatively correct description of the Kondo physics of dilute Fe impurities in Au or Ag. Such a description must meet the challenge of quantitatively reproducing, using the Kondo temperature T K as only fitting parameter, several independent sets of experimental measurements: the contributions by magnetic impurities (indicated by a subscript m) to the temperatureand field-dependence of the resistivity, ρ m (T, B), and to the temperature-dependence of the decoherence rate, γ m (T ), extracted from weak (anti)localization measurements. The spin-1 2 , 1-band Kondo model does not meet this challenge: when comparing its predictions, obtained by the numerical renormalization group (NRG) 4-6 , to transport measurements on dilute Fe impurities in Ag wires, different Kondo scales were required for fitting the resistivity and decoherence rates 7,8 .In a recent publication (Ref. 9, involving most of the present authors, henceforth referred to as paper I), it was argued that the proper effective low-energy Kondo model for Fe in Au or Ag is, in fact, a fully screened, spin-3 2 three-channel Kondo model. paper I arrived at this conclusion by the following chain of arguments. Previous transport experiments 7,8 had indicated that these sys-tems are described by a fully screened Kondo model 10-14 , i.e. a Kondo model in which the local spin, S, is related to the number of conduction bands, n, by S = n/2. As mentioned above, t...