We investigate the thermoelectric properties of a double quantum dot system coupled to two metallic reservoirs, focusing on main effects: (i) influence coupling asymmetry between and reservoirs Seebeck coefficient, (ii) impact in energy levels dots current rectification. In first case, we find that introducing moderate significantly enhances coefficient. second while rectification vanishes when are degenerate, substantial is achieved one level lies below other above Fermi level. further...

The universal scaling behavior is studied for nonequilibrium transport through a quantum dot. To describe the dot we use standard Anderson impurity model and non-equilibrium non-crossing approximation in limit of infinite Coulomb repulsion. After solving de hamiltonian, calculate conductance system as function temperature $T$ bias voltage $V$ Kondo mixed valent regime. We obtain good both regimes. In particular, regime, find excellent agreement with recent experiments previous theoretical works.

We review here some universal aspects of the physics two-electron molecular transistors in absence strong spin–orbit effects. Several recent quantum dot experiments have shown that an electrostatic backgate could be used to control energy dispersion magnetic levels. discuss how generally asymmetric coupling metallic contacts two different orbitals can indeed lead a gate-tunable Hund's rule presence singlet and triplet states dot. For gate voltages such constitutes (non-magnetic) ground...

We calculate the thermopower of a quantum dot described by two doublets hybridized with degenerate bands conducting leads, conserving orbital (band) and spin numbers, as function temperature $T$ splitting $\ensuremath{\delta}$ levels that breaks SU(4) symmetry. The can be regarded Zeeman (spin) or valley (orbital) splitting. use noncrossing approximation (NCA), slave bosons in mean-field (SBMFA), also numerical renormalization group (NRG) for large $\ensuremath{\delta}$. model describes...

We calculate the nonequilibrium conductance through a molecule or quantum dot in which occupation of relevant electronic level is coupled with intensity $\ensuremath{\lambda}$ to phonon mode and also two conducting leads. The system described by Anderson-Holstein Hamiltonian. solve problem using Keldysh formalism noncrossing approximation for both electron-electron electron-phonon interactions. obtain moderate decrease Kondo temperature ${T}_{K}$ fixed renormalized energy localized...

We study the low temperature properties of differential response current to a gradient at finite voltage in single level quantum dot including electron-electron interaction, non-symmetric couplings leads and non-linear effects. The calculated is significantly enhanced setups with large asymmetries between tunnel couplings. In investigated range voltages temperatures corresponding energies up several times Kondo energy scale, maximum nearly an order magnitude respect symmetric coupling leads.

We study the heat current through two capacitively coupled quantum dots in series with conducting leads at different temperatures $T_L$ and $T_R$ spinless case (valid for a high applied magnetic field). Our results are also valid single dot strongly ferromagnetic pointing opposite directions (so that electrons given spin can jump only to one lead) or degenerate levels destructive interference field. Although charge is always zero, finite when interdot Coulomb repulsion $U$ taken into account...

We obtain the quantum phase diagram of ionic Hubbard model including electron-hole symmetric density-dependent hopping. The boundaries phases are determined by crossings excited levels with particular discrete symmetries, which coincide jumps charge and spin Berry a topological meaning. Reducing magnitude hopping terms that do not change total number singly occupied sites respect to other one, region fully gapped spontaneously dimerized insulator (which separates band insulating Mott phases)...

We calculate the finite temperature and non-equilibrium electric current through systems described generically at low energy by a singlet \emph{two} spin doublets for $N$ $N \pm 1$ electrons respectively, coupled asymmetrically to two conducting leads, which allows destructive interference in conductance. The model is suitable studying transport great variety of such us aromatic molecules, different geometries quantum dots rings with applied magnetic flux. As consequence interplay between...

We calculate the nonequilibrium conductance of a system two capacitively coupled quantum dots, each one connected to its own pair conducting leads. The has been used recently perform pseudospin spectroscopy by controlling independently voltages four is defined orbital occupation or other dot. Starting from SU(4) symmetric point spin and degeneracy in Kondo regime, for an odd number electrons system, we show how through dot varies as symmetry reduced SU(2) pseudo-Zeeman splitting, bias are...

Starting from exact eigenstates for a symmetric ring, we derive low-energy effective generalized Anderson Hamiltonian which contains two spin doublets with opposite momenta and singlet the neutral molecule. For benzene, (doublets) represent ground state of (singly charged) We calculate non-equilibrium conductance through benzene molecule, doped one electron or hole (i.e. in Kondo regime), connected to conducting leads at different positions. solve problem using Keldysh formalism non-crossing...

We study the linear thermoelectric response of a quantum dot embedded in constriction Hall bar with fractional filling factors nu=1/m within Laughlin series. calculate figure merit ZT for maximum efficiency at fixed temperature difference. find significant enhancement this quantity relation to integer-filling case, which is direct consequence fractionalization electron state. present simple theoretical expressions Onsager coefficients low temperatures, explicitly show that and Seebeck...

We study the low-temperature properties of generalized Anderson impurity model in which two localized configurations, one with doublets and other a triplet, are mixed by degenerate conduction channels. By using numerical renormalization group non-crossing approximation, we analyze entropy, its spectral density, equilibrium conductance for several values parameters. Marked differences respect to conventional one-channel spin $s=1/2$ model, that can be traced as hallmarks an $S=1$, found Kondo...

We investigate theorerically the non-equilibrium transport through a molecular quantum dot as function of gate and bias voltage, taking into account typical situation in electronics. In this respect, our study includes asymmetries both capacitances tunneling rates to source drain electrodes, well an infinitely large charging energy on molecule. Our calculations are based out-of-equilibrium Non-Crossing-Approximation (NCA), which is reliable technique regime under consideration. find that...

We calculate the spectral density and occupations of a system two capacitively coupled quantum dots, each one connected to its own pair conducting leads, in regime parameters which total couplings leads for dot Γ(i) are different. The has been used recently perform pseudospin spectroscopy by controlling independently voltages four leads. For an odd number electrons system, equal coupling Γ1 = Γ2, levels E1 E2 sufficiently large interdot repulsion U12 lies SU(4) symmetric point spin...

In the present work, we calculate conductance through a single quantum dot weakly coupled to metallic contacts. We use spin-1/2 Anderson model describe dot, while considering finite Coulomb repulsion. solve interacting system using noncrossing approximation (NCA) and one-crossing (OCA). obtain linear response as function of temperature energy position localized level. From comparison both approximations extract role vertex corrections, which are introduced in OCA calculations neglected NCA...

We calculate the conductance as a function of temperature $G(T)$ through Au monatomic chains containing one Co atom magnetic impurity, and connected to two conducting leads with fourfold symmetry axis. Using information derived from ab initio calculations, we construct an effective model ${\stackrel{^}{H}}_{\mathrm{eff}}$ that hybridizes $3{d}^{7}$ quadruplet at site $3{d}^{8}$ triplets hopping $5{d}_{xz}$ $5{d}_{yz}$ electrons Au. The is split by spin anisotropy due spin-orbit coupling....

Using a combination of scanning tunneling spectroscopy and atomic lateral manipulation, we obtained systematic variation the Kondo temperature ($T_\mathrm K$) Co atoms on Ag(111) as function surface state contribution to total density states at atom adsorption site ($\rho_s$). By sampling $T_\mathrm K$ positions where $\rho_s$ was spatially resolved beforehand, obtain nearly linear relationship between both magnitudes. We interpret data basis an Anderson model including orbital spin degrees...

We study the thermoelectric response of a device containing pair helical edge states contacted at same temperature $T$ and chemical potential $\ensuremath{\mu}$ connected to an external reservoir, with different temperature, through side quantum dot. Different operational modes can be induced by applying magnetic field $B$ gate voltage ${V}_{g}$ At finite $B$, dot acts simultaneously as charge spin filter. Charge currents are induced, not only dot, but also along states. focus on linear...

The zero-bias anomaly at low temperatures, originated by the Kondo effect when an electric current flows through a system formed spin-$1/2$ quantum dot and two metallic contacts is theoretically investigated. In particular, we compare width of this $2T_{\rm NE}$ with that resonance in spectral density states $2T_{K}^{\rho}$, obtained from Fano fit corresponding curves also temperature, $T_K^G$, defined temperature evolution equilibrium conductance $G(T)$. contrast to $T_K^G$ found scale...

We formulate a general theory to study the time-dependent charge and energy transport of an adiabatically driven interacting quantum dot in contact with reservoir for arbitrary amplitudes driving potential. within this framework Anderson impurity model local ac gate voltage. show that exact adiabatic dynamics system is fully determined by behavior susceptibility frozen problem. At $T=0$, we evaluate dynamic response functions numerical renormalization group (NRG). The time-resolved heat...

The low temperature properties of single level molecular quantum dots including both, electron-electron and electron-vibration interactions, are theoretically investigated. calculated differential conductance in the Kondo regime exhibits not only zero bias anomaly but also side peaks located at voltages which coincide with multiples energy vibronic mode $V \sim \hbar\Omega/e$. We obtain that evolution two main satellite follows corresponding one peak when $\hbar\Omega \gg k_B T_K$, being $...