Nonlinear low-temperature transport of electrons through a multilevel quantum dot (original) (raw)
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Low-temperature transport in ac-driven quantum dots in the Kondo regime
Physical Review B, 2001
We present a fully nonequilibrium calculation of the low temperature transport properties of a quantum dot in the Kondo regime when an AC potential is applied to the gate voltage. We solve a time dependent Anderson model with finite on-site Coulomb interaction. The interaction self-energy is calculated up to second order in perturbation theory in the on-site interaction, in the context of the Keldysh non-equilibrium technique, and the effect of the AC voltage is taken into account exactly for all ranges of AC frequencies and AC intensities. The obtained linear conductance and time-averaged density of states of the quantum dot evolve in a non trivial way as a function of the AC frequency and AC intensity of the harmonic modulation..
Physical Review B, 2005
We investigate the nonequilibrium transport properties of a three-terminal quantum dot in the strongly interacting limit. At low temperatures, a Kondo resonance arises from the antiferromagnetic coupling between the localized electron in the quantum dot and the conduction electrons in source and drain leads. It is known that the local density of states is accessible through the differential conductance measured at the (weakly coupled) third lead. Here, we consider the multiterminal current-current correlations (shot noise and cross correlations measured at two different terminals). We discuss the dependence of the current correlations on a number of external parameters: bias voltage, magnetic field and magnetization of the leads. When the Kondo resonance is split by fixing the voltage bias between two leads, the shot noise shows a nontrivial dependence on the voltage applied to the third lead. We show that the cross correlations of the current are more sensitive than the conductance to the appearance of an external magnetic field. When the leads are ferromagnetic and their magnetizations point along opposite directions, we find a reduction of the cross correlations. Moreover, we report on the effect of dephasing in the Kondo state for a two-terminal geometry when the third lead plays the role of a fictitious voltage probe.
Theoretical Study of Non-Equilibrium Transport in Kondo Quantum Dots
2012
B.1.4 Cross-coefficient nσc k 1 σ → f † σ c kσ f σ (t 12,σ). .. .. .. .. B.1.5 Cross-coefficient nσc k 1 σ → c † kσ fσf σ (t 13,σ). .. .. .. .. B.1.6 Cross-coefficient f † σ c k 1σ f σ → c † kσ fσf σ (t 23,σ). .. .. .. . B.1.7 Cross-coefficient c † k 1σ fσf σ → f † σ c kσ f σ (t 32,σ). .. .. .. . B.1.8 Effective couplings nσf σ → f † σ c kσ f σ (t 2σ) and nσf σ → c † kσ fσf σ (t 3σ
2016
We review mechanisms of low-temperature electronic transport through a quantum dot weakly coupled to two conducting leads. Transport in this case is dominated by electron-electron interaction. At temperatures moderately lower than the charging energy of the dot, the linear conductance is suppressed by the Coulomb blockade. Upon further lowering of the temperature, however, the conductance may start to increase again due to the Kondo effect. We concentrate on lateral quantum dot systems and discuss the conductance in a broad temperature range, which includes the Kondo regime.
Linear Kondo conductance in a quantum dot
Journal of Physics: Condensed Matter, 2004
In a tunneling experiment across a quantum dot it is possible to change the coupling between the dot and the contacts at will, by properly tuning the transparency of the barriers and the temperature. Gate voltages allow for changes of the relative position of the dot addition energies and the Fermi level of the leads. Here we discuss the two limiting cases: weak and strong coupling in the tunneling Hamiltonian. In the latter case Kondo resonant conductance can emerge at low temperature in a Coulomb blockade valley. We give a pedagogical approach to the single channel Kondo physics at equilibrium and review the Nozières scattering picture of the correlated fixed point. We emphasize the effect of an applied magnetic field and show how an orbital Kondo effect can take place in vertical quantum dots tuned both to an even and an odd number of electrons at a level crossing. We extend the approach to the two channel overscreened Kondo case and discuss recent proposals for detecting the non Fermi Liquid fixed point which could be reached at strong coupling.
Time dependent quantum transport through Kondo correlated quantum dots
In this article, we review recent work about time dependent quantum transport through a quantum dot in Kondo regime. This represents a major step towards designing next generation transistors that are expected to replace current MOSFET's in a few years. We first discuss the effects of the density of states of gold contacts on the instantaneous conductance of an asymmetrically coupled quantum dot that is abruptly moved into Kondo regime via a gate voltage. Next, we investigate the effect of strong electron-phonon coupling on the dot on the instantaneous conductance. Finally, we discuss thermoelectric effects using linear response Onsager relations for a quantum dot that is either abruptly moved into Kondo regime or driven sinusoidally via a gate voltage. We explain encountered peculiarities in transport based on the behaviour of the density of states of the dot and the evolution of the Kondo resonance.
Low-temperature transport through a quantum dot: Finite-U results and scaling behavior
Physical Review B, 2002
The infinite-U Anderson model is applied to non-equilibrium transport through a quantum dot containing two spin levels weakly coupled to two leads. At low temperatures, the Kondo peak in the equilibrium density of states is split upon the application of a voltage bias. The split peaks, one at the chemical potential of each lead, are suppressed by non-equilibrium dissipation. In a magnetic field, the Kondo peaks shift away from the chemical potentials by the Zeeman energy, leading to an observable peak in the differential conductance when the non-equilibrium bias equals the Zeeman energy. PACS numbers: 72.15.Qm 73.40.Gk 73.20.Dx 73.50.Fq 1
Interpolative Method for Transport Properties of Quantum Dots in the Kondo Regime
Lecture Notes in Physics
We present an interpolative method for describing coherent transport through an interacting quantum dot. The idea of the method is to construct an approximate electron self-energy which becomes exact both in the limits of weak and strong coupling to the leads. The validity of the approximation is first checked for the case of a single (spin-degenerate) dot level. A generalization to the multilevel case is then discussed. We present results both for the density of states and the temperature dependent linear conductance showing the transition from the Kondo to the Coulomb blockade regime.
Kondo effect in a two-level quantum dot coupled to an external fermionic reservoir
Physica E: Low-dimensional Systems and Nanostructures, 2002
We investigate theoretically the linear conductance of a twolevel quantum dot as a function of the gate voltage and different strength of coupling to the external electronic system (the reservoir). Apart from the weak coupling regime, characterized by the Kondo-enhancement of the conductance in the spinful ground state, a strong coupling regime, which can be called mixed-valence (MV), is found. This regime is characterized by a qualitative change of the energy level structure in the dot, resulting in sub-and super-tunneling coupling of the levels, which in turn yield a novel temperature dependence of the Kondo effect in the quantum dot.
Spintronic transport and Kondo effect in quantum dots
2005
We investigate the spin-dependent transport properties of quantum-dot based structures where Kondo correlations dominate the electronic dynamics. The coupling to ferromagnetic leads with parallel magnetizations is known to give rise to nontrivial effects in the local density of states of a single quantum dot. We show that this influence strongly depends on whether charge fluctuations are present or absent in the dot. This result is confirmed with numerical renormalization group calculations and perturbation theory in the on-site interaction. In the Fermi-liquid fixed point, we determine the correlations of the electric current at zero temperature (shot noise) and demonstrate that the Fano factor is suppressed below the Poissonian limit for the symmetric point of the Anderson Hamiltonian even for nonzero lead magnetizations. We discuss possible avenues of future research in this field: coupling to the low energy excitations of the ferromagnets (magnons), extension to double quantum dot systems with interdot antiferromagnetic interaction and effect of spin-polarized currents on higher symmetry Kondo states such as SU(4).