Evolution of the Kondo Effect in a Quantum Dot Probed by Shot Noise

Yamauchi, Yoshiaki; Sekiguchi, Koji; Chida, Kensaku; Arakawa, Tomoyuki; Nakamura, Shuji; Kobayashi, Kensuke; Ono, Teruo; Fujii, T.; Sakano, Rui

doi:10.1103/physrevlett.106.176601

Cited by 87 publications

(89 citation statements)

References 37 publications

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“…, an enhancement of the current fluctuations is detected out of equilibrium and perfectly explained by an e ective charge induced by the residual interaction between quasi-particles 8, [10][11][12][13][14][15][16][17] . Moreover, an as-yet-unknown scaling law for the e ective charge is discovered, suggesting a new non-equilibrium universality.…”

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confidence: 66%

“…This value, closely related to the Wilson ratio, is universal for the Fermi liquid in the Kondo regime as it depends only on the symmetry group of the system [13][14][15] . Although some aspects of Kondo-associated noise have been reported 8,16,17 , a rigorous, selfconsistent treatment in a regime where universal results apply is at the core of the present work. Actually, by investigating the same nanotube quantum dot in the spin degenerate SU(2) Kondo regime and in the spin-orbit degenerate SU(4) regime, the noise is proved to contain distinct signatures of these two symmetries, confirming theoretical developments of Fermi liquid theory out of equilibrium.…”

Section: The Kondo Effectmentioning

confidence: 96%

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Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

et al. 2015

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Interacting quantum many-body systems constitute a fascinating research field because they form quantum liquids with remarkable properties and universal behaviour The idea is that they behave as an ensemble of non-interacting 'quasi-particles'. However, non-equilibrium properties have still to be established and remain a key issue of many-body physics. Here, we show a precise experimental demonstration of Landau Fermi liquid theory extended to the non-equilibrium regime in a zero-dimensional system. Combining transport and ultra-sensitive current noise measurements, we have unambiguously identified the SU(2) (ref. The Kondo effect19 is a typical example of a quantum manybody effect, where a localized spin is screened by the surrounding conduction electrons at low temperature to form a unique correlated ground state. The Kondo state is described well by the Fermi liquid theory at equilibrium 1,9 , which makes it an ideal testbed to go beyond equilibrium. To unveil the universal behaviour of nonequilibrium Fermi liquid 11 , we have used the current fluctuations or shot noise in a Kondo-correlated nanotube quantum dot 18 . When electrons are transmitted through this system, the scattering induces the shot noise, which sensitively reflects the nature of the quasi-particles 20 , as shown in the upper panel of Fig. 1a. A remarkable prediction of the non-equilibrium Fermi liquid theory is that the residual interaction between quasi-particles creates an additional scattering of two quasi-particles which enhances the noise (see the lower panel of Fig. 1a) 10,12-15 . This two-particle scattering is characterized by an effective charge e * larger than e (electron charge). This value, closely related to the Wilson ratio, is universal for the Fermi liquid in the Kondo regime as it depends only on the symmetry group of the system [13][14][15] . Although some aspects of Kondo-associated noise have been reported 8,16,17 , a rigorous, selfconsistent treatment in a regime where universal results apply is at the core of the present work. Actually, by investigating the same nanotube quantum dot in the spin degenerate SU(2) Kondo regime and in the spin-orbit degenerate SU(4) regime, the noise is proved to contain distinct signatures of these two symmetries, confirming theoretical developments of Fermi liquid theory out of equilibrium.In our experiment, we measured the conductance and current noise through a carbon nanotube quantum dot grown by chemical vapour deposition 21 . Iron catalyst was deposited on an oxidized undoped silicon wafer and exposed to 10 mbar of acetylene for 9 s at 900• C. The nanotube was connected with a Pd(6 nm)/Al(70 nm) bilayer deposited by e-gun evaporation. The distance between the contacts is 400 nm and a side gate electrode is deposited to tune the potential of the quantum dot (see Fig. 1b). A magnetic field of 0.08 T is applied to suppress superconductivity of the contacts. To measure accurately the shot noise, our sample is connected to a resonant (2.58 MHz) LC circuit thermalized at the mixing chambe...

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confidence: 66%

Section: The Kondo Effectmentioning

confidence: 96%

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

et al. 2015

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“…Since this theory is based on the single-particle picture, additional information such as the many-body interaction may be deduced from the precise investigation of the Fano factor combined with the conductance, as we see in the shot noise study in the Kondo regime [19][20][21][22] . Actually, the shot noise of QPC was addressed by several experimental groups; the Pauli exclusion principle was first studied, and then the quantum interference 23 , the 0.7 anomaly [24][25][26] , and the spin polarization 25,27 .…”

Section: Introductionmentioning

confidence: 99%

Finite shot noise and electron heating at quantized conductance in high-mobility quantum point contacts

et al. 2016

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We report a precise experimental study on the shot noise of a quantum point contact (QPC) fabricated in a GaAs/AlGaAs based high-mobility two-dimensional electron gas (2DEG). xThe combination of unprecedented cleanliness and very high measurement accuracy has enabled us to discuss the Fano factor to characterize the shot noise with a precision of 1 %. We observed that the shot noise at zero magnetic field exhibits a slight enhancement exceeding the single particle theoretical prediction, and that it gradually decreases as a perpendicular magnetic field is applied. We also confirmed that this additional noise completely vanishes in the quantum Hall regime. These phenomena can be explained by the electron heating effect near the QPC, which is suppressed with increasing magnetic field.

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“…[3][4][5][6][7][8] Specifically, the orbital degeneracy affects the nonequilibrium current and current noise of quantum dots driven by the bias voltage eV , and has recently been studied in the low-energy Fermi-liquid regime.…”

Section: Introductionmentioning

confidence: 99%

Exact Green's function for a multiorbital Anderson impurity at high bias voltages

Oguri

Sakano

2015

Phys. Rev. B

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We study the nonequilibrium Keldysh Green's function for an N -orbital Anderson model at high bias voltages, extending a previous work which for the case only with the spin degrees of freedom N = 2, to arbitrary N . Our approach uses an effective non-Hermitian Hamiltonian that is defined with respect to a Liouville-Fock space in the context of a thermal field theory. The result correctly captures the relaxation processes at high energies, and is asymptotically exact not only in the highbias limit but also in the high-temperature limit at thermal equilibrium. We also present an explicit continued-fraction representation of the Green's function. It clearly shows that the imaginary part is recursively determined by the decay rate of intermediate states with at most N − 1 particle-holepair excitations. These high-bias properties follow from the conservations of a generalized charge and current in the Liouville-Fock space. We also examine temperature dependence of the spectral function in equilibrium, comparing the exact results with the numerical finite-T and analytical T → ∞ results of the non-crossing approximation (NCA).

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Evolution of the Kondo Effect in a Quantum Dot Probed by Shot Noise

Cited by 87 publications

References 37 publications

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

Universality of non-equilibrium fluctuations in strongly correlated quantum liquids

Finite shot noise and electron heating at quantized conductance in high-mobility quantum point contacts

Exact Green's function for a multiorbital Anderson impurity at high bias voltages

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