KONDO EFFECT AND SPIN-CHARGE SEPARATION IN QUANTUM DOTS

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1426-1442
Author(s):  
L. I. GLAZMAN ◽  
F. W. J. HEKKING ◽  
A. I. LARKIN
Keyword(s):  
Quantum Dot ◽  
Charge Separation ◽  
Coulomb Blockade ◽  
Kondo Effect ◽  
Broad Band ◽  
Single Mode ◽  
Kondo Temperature ◽  
Average Charge ◽  
Opposite Case ◽  
Anderson Impurity Model

The Kondo effect in a quantum dot is discussed. In the standard Coulomb blockade setting, tunneling between the dot and the leads is weak, the number of electrons in the dot is well-defined and discrete; the Kondo effect may be considered in the framework of the conventional one-level Anderson impurity model. It turns out however, that the Kondo temperature TK in the case of weak tunneling is extremely low. In the opposite case of almost reflectionless single-mode junctions connecting the dot to the leads, the average charge of the dot is not discrete. Surprisingly, its spin may remain quantized: s=1/2 or s=0, depending (periodically) on the gate voltage. Such a "spin-charge separation" occurs because, unlike an Anderson impurity, a quantum dot carries a broad-band, dense spectrum of discrete levels. In the doublet state, the Kondo effect develops with a significantly enhanced TK. Like in the weak-tunneling regime, the enhanced TK exhibits strong mesoscopic fluctuations. The statistics of the fluctuations is universal, and related to the Porter-Thomas statistics of the wave function fluctuations.

scholarly journals Nonequilibrium Kondo effect in a graphene-coupled quantum dot in the presence of a magnetic field

2020 ◽  
Vol 11 ◽  
pp. 225-239
Author(s):  
Levente Máthé ◽  
Ioan Grosu
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Quantum Dot ◽  
Coulomb Interaction ◽  
Coulomb Blockade ◽  
Kondo Effect ◽  
Dirac Point ◽  
Analytical Formula ◽  
Kondo Temperature ◽  
Hole Doping

Background: Quantum dots connected to larger systems containing a continuum of states like charge reservoirs allow the theoretical study of many-body effects such as the Coulomb blockade and the Kondo effect. Results: Here, we analyze the nonequilibrium Kondo effect and transport phenomena in a quantum dot coupled to pure monolayer graphene electrodes under external magnetic fields for finite on-site Coulomb interaction. The system is described by the pseudogap Anderson Hamiltonian. We use the equation of motion technique to determine the retarded Green’s function of the quantum dot. An analytical formula for the Kondo temperature is derived for electron and hole doping of the graphene leads. The Kondo temperature vanishes in the vicinity of the particle–hole symmetry point and at the Dirac point. In the case of particle–hole asymmetry, the Kondo temperature has a finite value even at the Dirac point. The influence of the on-site Coulomb interaction and the magnetic field on the transport properties of the system shows a tendency similar to the previous results obtained for quantum dots connected to metallic electrodes. Most remarkably, we find that the Kondo resonance does not show up in the density of states and in the differential conductance for zero chemical potential due to the linear energy dispersion of graphene. An analytical method to calculate self-energies is also developed which can be useful in the study of graphene-based systems. Conclusion: Our graphene-based quantum dot system provides a platform for potential applications of nanoelectronics. Furthermore, we also propose an experimental setup for performing measurements in order to verify our model.

scholarly journals Spin-Charge Separation and the Kondo Effect in an Open Quantum Dot

1999 ◽  
Vol 83 (9) ◽  
pp. 1830-1833 ◽  
Author(s):  
L. I. Glazman ◽  
F. W. J. Hekking ◽  
A. I. Larkin
Keyword(s):  
Quantum Dot ◽  
Charge Separation ◽  
Kondo Effect ◽  
Open Quantum

scholarly journals Quantum Transport Through a ``Charge" Kondo Circuit: Effects of Weak Repulsive Interaction in Luttinger Liquid

2020 ◽  
Vol 30 (1) ◽  
pp. 1
Author(s):  
Thanh Thi Kim Nguyen ◽  
Mikhail N. Kiselev
Keyword(s):  
Quantum Transport ◽  
Coulomb Blockade ◽  
Quantum Interference ◽  
Kondo Effect ◽  
Single Channel ◽  
Point Contact ◽  
Luttinger Liquid ◽  
Single Mode ◽  
Quantum Circuit ◽  
Repulsive Interaction

We investigate theoretically quantum transport through the ``charge" Kondo circuit consisting of the quantum dot (QD) coupled weakly to an electrode at temperature \(T+\Delta T\) and connected strongly to another electrode at the reference temperature \(T\) by a single-mode quantum point contact (QPC). To account for the effects of Coulomb interaction in the QD-QPC setup operating in the integer quantum Hall regime we describe the edge current in the quantum circuit by Luttinger model characterized by the Luttinger parameter \(g\). It is shown that the temperature dependence of both electric conductance \(G\propto T^{2/g}\) and thermoelectric coefficient \(G_T\propto T^{1+2/g}\) detours from the Fermi-liquid (FL) theory predictions. The behaviour of the thermoelectric power \(S=G_T/G\propto T\) in a regime of a single-channel Kondo effect is, by contrast, consistent with the FL paradigm. We demonstrate that the interplay between the mesoscopic Coulomb blockade in QD and weak repulsive interaction in the Luttinger Liquid \(g=1-\alpha\) \((\alpha \ll 1)\) results in the enhancement of the thermopower. This enhancement is attributed to suppression of the Kondo correlations in the ``charge" circuit by the destructive quantum interference effects.

scholarly journals Coulomb blockade and Kondo effect in a few-electron silicon/silicon-germanium quantum dot

2007 ◽  
Vol 90 (3) ◽  
pp. 033103 ◽  
Author(s):  
Levente J. Klein ◽  
Donald E. Savage ◽  
Mark A. Eriksson
Keyword(s):  
Quantum Dot ◽  
Silicon Germanium ◽  
Coulomb Blockade ◽  
Kondo Effect ◽  
Silicon Silicon

Broad-band lead halide perovskite quantum dot single-mode lasers

2020 ◽  
Vol 8 (39) ◽  
pp. 13642-13647
Author(s):  
Chun Zhou ◽  
Jie Yu ◽  
Hongxing Dong ◽  
Fanglong Yuan ◽  
Xiaopeng Zheng ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Broad Band ◽  
Visible Region ◽  
Single Mode ◽  
Halide Perovskite ◽  
Lead Halide

We obtained broad-band CQD single-mode lasers across the entire visible region through combining CQDs with a microcavity.

scholarly journals Kondo effect and superconductivity in niobium with iron impurities

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hansong Zeng ◽  
Dan Zhou ◽  
Guoqing Liang ◽  
Rujun Tang ◽  
Zhi H. Hang ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Low Temperatures ◽  
Kondo Effect ◽  
Film Structure ◽  
Kondo Temperature ◽  
Superconducting Transition ◽  
Interesting Phenomenon ◽  
Superconducting Device ◽  
Bcc Lattice ◽  
Device Applications

AbstractKondo effect is an interesting phenomenon in quantum many-body physics. Niobium (Nb) is a conventional superconductor important for many superconducting device applications. It was long thought that the Kondo effect cannot be observed in Nb because the magnetic moment of a magnetic impurity, e.g. iron (Fe), would have been quenched in Nb. Here we report an observation of the Kondo effect in a Nb thin film structure. We found that by co-annealing Nb films with Fe in Argon gas at above 400 $$^{\circ }$$ ∘ C for an hour, one can induce a Kondo effect in Nb. The Kondo effect is more pronounced at higher annealing temperature. The temperature dependence of the resistance suggests existence of remnant superconductivity at low temperatures even though the system never becomes superconducting. We find that the Hamann theory for the Kondo resistivity gives a satisfactory fitting to the result. The Hamann analysis gives a Kondo temperature for this Nb–Fe system at $$\sim $$ ∼ 16 K, well above the superconducting transition onset temperature 9 K of the starting Nb film, suggesting that the screening of the impurity spins is effective to allow Cooper pairs to form at low temperatures. We suggest that the mechanism by which the Fe impurities retain partially their magnetic moment is that they are located at the grain boundaries, not fully dissolved into the bcc lattice of Nb.

Spin-bias modulated Kondo effect in an interacting quantum dot

2012 ◽  
Vol 111 (7) ◽  
pp. 07C309
Author(s):  
Yuan Li ◽  
M. B. A. Jalil ◽  
Seng Ghee Tan
Keyword(s):  
Quantum Dot ◽  
Kondo Effect

The direct observation of charge separation dynamics in CdSe quantum dots/cobaloxime hybrids

2016 ◽  
Vol 18 (6) ◽  
pp. 4300-4303 ◽  
Author(s):  
J. Huang ◽  
Y. Tang ◽  
K. L. Mulfort ◽  
X. Zhang
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Charge Separation ◽  
Cdse Quantum Dots ◽  
X Ray ◽  
Molecular Catalyst ◽  
Cdse Quantum Dot ◽  
Photoinduced Charge Separation ◽  
X Ray Absorption ◽  
Photoinduced Charge

In this work, we investigated photoinduced charge separation dynamics in a CdSe quantum dot/cobaloxime molecular catalyst hybrid using the combination of transient optical (OTA) and X-ray absorption (XTA) spectroscopy.

scholarly journals Ferromagnetic Kondo Effect in a Triple Quantum Dot System

2013 ◽  
Vol 111 (4) ◽  
Author(s):  
P. P. Baruselli ◽  
R. Requist ◽  
M. Fabrizio ◽  
E. Tosatti
Keyword(s):  
Quantum Dot ◽  
Kondo Effect
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