Kondo Effect in a Quantum Dot Coupled to Ferromagnetic Leads: A Numerical Renormalization Group Analysis

Choi, Myeon-Song; Sánchez, David; López, Rosa

doi:10.1103/physrevlett.92.056601

Cited by 182 publications

(231 citation statements)

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“…36 A spin-dependent hybridization for the spin-up and spin-down energy levels of the impurity is then predicted, resulting in an effective static magnetic field at the impurity site (this field can eventually be compensated by an external magnetic field). 29,31,35 In the presence of ferromagnetism, the Kondo resonance therefore splits apart as confirmed experimentally. 32,37 While such a splitting is well understood, the impact of a nonequilibrium spin current on the Kondo resonance has so far been little addressed in correlated nanostructures.…”

Section: Introductionmentioning

confidence: 71%

“…[12][13][14][15][16] It has also been successfully evidenced in nanoscale devices, [17][18][19][20][21] in particular quantum dots, [17][18][19][22][23][24] carbon nanotubes, [25][26][27] and nanowires. 28 Of particular interest-especially in the context of spintronics, is the issue of screening in the presence of a magnetic environment such as spin-polarized electrodes [29][30][31][32][33][34][35] and spinpolarized edge states. 36 A spin-dependent hybridization for the spin-up and spin-down energy levels of the impurity is then predicted, resulting in an effective static magnetic field at the impurity site (this field can eventually be compensated by an external magnetic field).…”

Section: Introductionmentioning

confidence: 99%

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Nonequilibrium spin-current detection with a single Kondo impurity

et al. 2013

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We present a theoretical study based on the Anderson model of the transport properties of a Kondo impurity (atom or quantum dot) connected to ferromagnetic leads, which can sustain a nonequilibrium spin current. We analyze the case where the spin current is injected by an external source and when it is generated by the voltage bias. Due to the presence of ferromagnetic contacts, a static exchange field is produced that eventually destroys the Kondo correlations. We find that such a field can be compensated by an appropriated combination of the spin-dependent chemical potentials leading to the restoration of the Kondo resonance. In this respect, a Kondo impurity may be regarded as a very sensitive sensor for nonequilibrium spin phenomena.

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Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Nonequilibrium spin-current detection with a single Kondo impurity

et al. 2013

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“…or a carbon nanotube 21 contacted with ferromagnetic leads has been justified by the oppositely directed spin polarizations in the electrodes, in agreement with refs. 22,23,24 . Although the situation regarding the magnetization of the leads might be similar in our system, we argue that the Kondo effect is still possible even if there is no domain wall pinned in the contact.…”

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confidence: 99%

The Kondo effect in ferromagnetic atomic contacts

Calvo

Fernández-Rossier

Palacios

et al. 2009

Nature

143

168

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Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in these materials takes place mainly through the s and p electrons, whereas the magnetic moments are mostly in the narrow d-electron bands, where they tend to align. This general picture may change at the nanoscale because electrons at the surfaces of materials experience interactions that differ from those in the bulk. Here we show direct evidence for such changes: electronic transport in atomic-scale contacts of pure ferromagnets (iron, cobalt and nickel), despite their strong bulk ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of local magnetic moments by the conduction electrons below a characteristic temperature 1 . The Kondo effect creates a sharp resonance at the Fermi energy, affecting the electrical properties of the system;this appears as a Fano-Kondo resonance 2 in the conductance characteristics as observed in other artificial nanostructures 3,4,5,6,7,8,9,10,11 . The study of hundreds of contacts shows material-dependent lognormal distributions of the resonance width that arise naturally from Kondo theory 12 . These resonances broaden and disappear with increasing temperature, also as in standard Kondo systems 4,5,6,7 . Our observations, supported by calculations, imply that coordination changes can significantly modify magnetism at the nanoscale. Therefore, in addition to standard micromagnetic physics, strong electronic correlations along with atomic-scale geometry need to be considered when investigating the magnetic properties of magnetic nanostructures.Atomic-scale contacts can be fabricated by techniques such as scanning tunnelling microscopy 13 or the use of electromigrated break junctions (EBJs) 14 , where the size of a macroscopic contact between two leads is reduced until they are in contact through only a few atoms and, eventually, through only one. The conductance of metallic monatomic contacts is known to be around 2G 0 , where G 0 = e 2 /h is the spin-resolved quantum of conductance 13 (e being the elementary charge and h Planck ′ s constant). To identify the atomic contacts, histograms are constructed from the evolution of the conductance recorded during the breaking of different contacts (Fig. 1a, b). The position of the first peak of these histograms is identified as the conductance of the monatomic contact. For iron, cobalt and nickel, the conductance is larger than 2G 0 owing to the contribution of the sp and d orbitals to the transmission 15,16,17 .We have studied the low-temperature conductance characteristics of hundreds of atomic-scale contacts of the three transition-metal ferromagnets iron, cobalt and nickel using a home-built STM. More than the 80% of the differential conductance (dI/dV ) curves at the monatomic contact show peaks or dips around zero bias such as those shown in Fig. 1c, which are very similar to those observed in STM spectroscopy of single magnetic adatoms on non-magnetic surfaces 9,10,11 . Thus, as in the case of these Kondo systems, we ca...

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“…(27) is given as a Dyson-like equation which is better seen by introducing the bare GF g satisfying the equation (iωI −∆ 0 )g(iω) = P. Then Eq. (27) can be re-written as…”

Section: B Transport Equation In the Hubbard I Approximationmentioning

confidence: 99%

“…atomic limit, non-interacting limit (on-site Coulomb repulsion U → 0), and the strongly correlated limit (U → ∞). While these limits have been treated several times, and the last limit has been treated in detail concerning Kondo physics, 22,23,24,25,26,27 it is important that the here presented material includes these limits. It is also important to note that the renormalisation of the localised level often discussed in scaling theory, 15,16,17,18,19,20,21 is included into the present formulation.…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium theory for a quantum dot with arbitrary on-site correlation strength coupled to leads

Fransson

2005

Phys. Rev. B

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An analytical expression for the current through a single level quantum dot for arbitrary strength of the on-site electron-electron interaction is derived beyond standard mean-field theory. By describing the localised states in terms of many-body operators, the employed diagrammatic technique for strong coupling enables inclusion of electron correlation effects into the description of the local dynamics, which provides transport properties that are consistent with recent experimental data.

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Kondo Effect in a Quantum Dot Coupled to Ferromagnetic Leads: A Numerical Renormalization Group Analysis

Cited by 182 publications

References 32 publications

Nonequilibrium spin-current detection with a single Kondo impurity

Nonequilibrium spin-current detection with a single Kondo impurity

The Kondo effect in ferromagnetic atomic contacts

Nonequilibrium theory for a quantum dot with arbitrary on-site correlation strength coupled to leads

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