Electronic transport through a quantum dot strongly coupled to electrodes is studied within model with two conduction channels. It shown that multiple scattering and interference of transmitted waves both channels lead Fano resonance associated Kondo resonance. Interference effects are also pronouncedly seen in the Aharonov-Bohm ring dot, where current characteristics continuously evolve magnetic flux.

Current and its noise in a ferromagnetic double tunnel barrier device with small spacer particle were studied the framework of sequential tunneling approach. Analytical formulas derived for electron through containing only single energy level. It was shown that Coulomb interactions electrons different spin orientation lead to an increase magnetoresistance. Interactions can also be responsible negative differential resistance. A current study showed which relaxation processes enhance or...

Coherent electronic transport through a double quantum dot (2qd) system connected in series with electrodes is studied by means of nonequilibrium Green functions and using the equation motion method, which all electron correlations 2qd are treated exactly. For moderate Coulomb interactions we predict features conductance characteristics resulting from transmission triplet states, can be strongly activated for larger source-drain voltages. The analysis spin-spin correlation shows strong...

We consider a coherent electronic transport between two ferromagnetic electrodes separated either by metallic nanoparticle or conducting molecule. Correlations electrons with opposite spins lead to the Kondo resonance, which manifests formation of singlet state. Although tunneling rates for spin orientations are different, conductance reaches unitary limit in regime. predict negative magnetoresistance effect, can be observed asymmetric magnetic junctions.

Frequency dependent current noise in ferromagnetic double junctions with Coulomb blockade is studied theoretically the limit of sequential tunneling. Two different relaxation processes are found correlations between spin polarized tunneling currents; low frequency fluctuations and high charge fluctuations. Spin accumulation strongly asymmetric shown to lead a negative differential resistance. We also show that large activated range resistance gives rise significant enhancement noise.

Electron tunneling in ferromagnetic single-electron transistors is considered theoretically the sequential regime. A new formalism developed, which operates a two-dimensional space of states, instead one-dimensiona used spinless case. It shown that spin fluctuations can be significantly larger than charge fluctuations. The influence discrete energy spectrum small central electrode on current, and accumulation, fluctuations, tunnel magnetoresistance analyzed details. Two different scales are...

We analyze transport properties of coherent triple-quantum-dot systems in triangular geometry, weakly coupled to external leads. The real-time diagrammatic technique up the second order is used determine conductance and shot noise sequential tunneling cotunneling regimes. In particular, we focus on regime where triple dot trapped a dark state system interchannel Coulomb blockade, which leads negative differential conductance. show that although then exponentially suppressed, blockade can be...

The phase diagrams and superconducting properties of the extended Hubbard model with pair hopping interaction, i.e., Penson-Kolb-Hubbard are studied. analysis is performed for d-dimensional hypercubic lattices, including $d=1$ $d=\ensuremath{\infty},$ by means (broken symmetry) Hartree-Fock approximations and, slave-boson mean-field method. For $d=1,$ at half filling diagram shown to consist nine different phases two states center-of-mass momentum $q=0$ $q=Q$ $(\ensuremath{\eta}$ pairing),...

We consider, within the Hubbard model, nonequilibrium transport through a triangular molecule [or, equivalently, triple quantum dot system (3QD)], weakly coupled to electrodes. The exact solution of eigenproblem for isolated 3QD is used computation current-voltage $(I\text{\ensuremath{-}}V)$ characteristics device in sequential tunneling limit. analyze effects symmetry perturbation and show that local energy at one sites electrodes can lead negative differential resistance as well rectifying...

We analyze changes of the electronic structure a triangular molecule under influence an electric field (i.e., Stark effect). The effects are shown to be anisotropic and include both linear nonlinear part. For strong electron correlations, we explicitly derive exchange couplings in effective spin Hamiltonian. some conditions one can find dark state, for which spins is decoupled from others. model also applied studying transport through system three coherently coupled quantum dots. Since...

The interplay between various many-body effects in a quantum dot attached to two normal and one superconducting lead is considered the limit of large gap. By proximity effect induces pairing correlations on dot. In subgap region observes anomalous tunneling via direct crossed Andreev scattering, whereas usual single particle electronic transfer suppressed. interactions electrons leading such phenomena as Coulomb blockade Kondo severely modify currents flowing system. particular: (i) They...

The thermoelectric effects in three-terminal structures with a quantum dot are considered. We propose the experimentally consistent protocol for determination of transport coefficients terms local and nonlocal conductances thermopowers that can be measured two steps, applying ``four-probe technique''. This proposal is compared other approaches discussed literature. As an example, we study detail thermopower induced by superconducting electrode subgap regime which might useful analysis novel...

The transport properties of an octane-dithiol (ODT) molecule coupled to Au(001) leads are analyzed using density-functional theory (DFT) and nonequilibrium Green's functions. It is shown that a symmetric can turn into diode under influence local electric field created by external charged probe. origin the asymmetry current-voltage $(I\text{\ensuremath{-}}V)$ dependence traced back appearance probe-induced quasilocal state in pseudogap ODT molecule. induced affects electron provided it close...

We study generation and dynamics of an exchange spin qubit encoded in three coherently coupled quantum dots with electrons. For two geometries the system, a linear triangular one, creation coherent control states are performed by Landau–Zener transitions. In case, both equivalent can be easily generated for particular symmetries system. If one is smaller than others, observe Rabi oscillations that used manipulation states. The system easier to fabricate; however, then not equivalent, making...

Linear conductance across a large quantum dot via single level ${ϵ}_{0}$ with hybridization to the contacts is strongly sensitive quasibound states localized in and weakly coupled ${ϵ}_{0}$. The oscillates gate voltage due interference of Fano type. At low temperature Coulomb blockade, Kondo correlations damp oscillations on an extended range values, by freezing occupancy itself. As consequence, antiresonances origin are washed out. results good correspondence experimental data for semiopen regime.

We model a small quantum dot with magnetic impurity by the Anderson Hamiltonian supplementary exchange interaction term. The transport calculations are performed means of Green functions within equation motion scheme, in which two decoupling procedures proposed, for high and low temperatures, respectively. paper focuses on charge fluctuations such system, an aspect not addressed before, as well Kondo resonance. show specific role excited state, can be observed spin-spin correlations. Our...

We investigate the electrical conductance and thermopower of a quantum dot tunnel coupled to external leads described by an extension Anderson impurity model which takes into account assisted hopping processes, i.e., occupancy-dependence tunneling amplitudes. provide analytical understanding based on scaling arguments Schrieffer–Wolff transformation, corroborated detailed numerical calculations using renormalization group method. The modifies coupling two-particle state, shifts Kondo...

We consider a triple quantum dot system in triangular geometry with one of the dots connected to metallic leads. Using Wilson's numerical renormalization group method, we investigate entanglement and its relation thermodynamic transport properties, regime where each is singly occupied on average, but non-negligible charge fluctuations. It shown that even significant fluctuations formation Kondo singlets induces switching between separable perfectly entangled states. The phase transition...

Transport properties of short molecular chains connecting metallic electrodes are studied within the one-band Hubbard model taking into account electron Coulomb interactions in self-consistent (Hartree-Fock) approximation. The current-voltage characteristics represented as a sequence voltage ranges differing number channels dominating transport. These originate from energy (SCE) levels trapped source-drain window. new qualitative effect repulsion is pinning SCE by Fermi source or drain lead...

We present a model of qubit built three coherently coupled quantum dots with spins in triangular geometry. The states are encoded the doublet subspace and they controlled by gate voltage, which breaks symmetry system. show how to prepare perform one operations. A new type current blockade effect will be discussed. is related an asymmetry transfer rates from electrodes different used read-out dynamics state. Our research also presents analysis Rabi oscillations, decoherence leakage processes...

We present a procedure for calculation of transport characteristics molecular junctions. It is based on the nonequilibrium Green's functions and exploits Hubbard operators, which allows us to treat formally exactly all electron correlations within molecule. The reproduces exact results in limiting cases: weak molecule-lead coupling high temperatures (i.e., Coulomb blockade limit), limit vanishing interactions. Between these limits method can be applied as an interpolating scheme. As example...