The ability to make electrical contact single molecules creates opportunities examine fundamental processes governing electron flow on the smallest possible length scales. We report experiments in which we controllably stretched individual cobalt complexes having spin S = 1, while simultaneously measuring current through molecule. molecule's states and magnetic anisotropy were manipulated absence of a field by modification molecular symmetry. This control enabled quantitative studies...

Femtosecond time-resolved photoemission is used to investigate the time evolution of electronic structure in Mott insulator 1T-TaS2. A collapse gap observed within 100 femtoseconds after optical excitation. The spectra and spectral function calculated by dynamical mean field theory show that this insulator-metal transition driven solely hot electrons. coherently excited lattice displacement results a periodic shift lasting for 20 ps without perturbing insulating phase. This capability...

We present an approach to the normal state of cuprate superconductors which is based on a minimal cluster extension dynamical mean-field theory. Our effective two-impurity model embedded in self-consistent bath. The two degrees freedom this can be associated nodal and antinodal regions momentum space. find metal-insulator transition selective At low doping, quasiparticles are destroyed region, while they remain protected leading formation apparent Fermi arcs. compare our results tunneling...

The transport properties of a double quantum dot device with one the dots coupled to perfect conductors are analyzed using numerical renormalization group technique and slave-boson mean-field theory. coupling between strongly influences through system, leading nonmonotonic dependence conductance as function temperature magnetic field. For small interdot parameters such that both in Kondo regime, there is two-stage screening dot's moments reflected conductance. In an intermediate-temperature...

The conductance through a molecular device including electron-electron and electron-phonon interactions is calculated using the numerical renormalization group method. At low temperatures weak coupling properties of can be explained in terms standard Kondo model with renormalized parameters. large charge analog effect takes place that mapped into an anisotropic model. In this regime molecule strongly polarized by gate voltage which leads to rectification current-voltage characteristics junction.

The problem of a magnetic impurity, atomic or molecular, absorbed on top carbon atom in otherwise clean graphene is studied using the numerical renormalization group. spectral, thermodynamic, and scattering properties impurity are described detail. In presence small field, low-energy electronic features make it possible to inject spin-polarized currents through scanning tunneling microscope. Furthermore, becomes strongly spin dependent for finite concentration leads bulk large...

We study the electronic structure of diluted F atoms chemisorbed on graphene using density functional theory calculations. show that nature chemical bonding a atom adsorbed top C in strongly depends carrier doping. In neutral samples impurities induce sp^3-like below, generating local distortion hexagonal lattice. As is electron-doped, retracts back to plane and for high doping (10^14 cm^-2) its corresponds nearly pure sp^2 configuration. interpret this sp^3-sp^2 doping-induced crossover...

The linear transport properties of a model molecular transistor with electron-electron and electron-phonon interactions were investigated analytically numerically. takes into account phonon modulation the electronic energy levels tunnelling barrier between molecule electrodes. When both effects are present they lead to asymmetries in dependence conductance on gate voltage. Kondo effect is observed presence interactions. There important qualitative differences cases weak strong coupling. In...

Using density-functional-theory (DFT), Hartree-Fock, exact-diagonalization, and numerical-renormalization-group methods, we study the electronic structure of diluted hydrogen atoms chemisorbed on graphene. A comparison between DFT Hartree-Fock calculations allows us to identify main characteristics magnetic defect. We use this information formulate an Anderson-Hubbard model that captures physical ingredients system while still allowing a rigorous treatment correlations. find large...

A periodic lattice distortion that reduces the translational symmetry folds electron bands into a reduced Brillouin zone, leading to band mixing and tendency gap formation, as in Peierls transition one-dimensional systems. However, higher dimensions, resulting phase can present topological obstructions preventing complete opening. We discuss two different mechanisms for such obstructions, emergent Weyl nodes protected crossings. Based on density-functional calculations, we show these are at...

The Kondo effect in quantum dots attached to ferromagnetic leads with general polarization directions is studied combining poor man scaling and Wilson's numerical renormalization group methods. We show that polarized electrodes will lead a splitting of the resonance dot density states except for small range angles close antiparallel case. also an external magnetic field able compensate this restore unitary limit. Finally, we study electronic transport through device various limiting cases.

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 present results for Kondo impurities in nanoscopic systems. Using exact diagonalization small clusters and Wilson's renormalization group we analyze an isolated system a weakly coupled to macroscopic reservoir. In the latter case, new regimes not observed homogeneous systems are induced by confinement of conduction electrons. These confinement-induced very different depending on whether Fermi energy coincides with resonant state or lies between two quasi-bound states.

We study the transport through a quantum dot, in Kondo Coulomb blockade valley, embedded mesoscopic device with finite wires. The quantization of states circuit that hosts dot gives rise to size effects. These effects make conductance sensitive ratio screening length wires and provide way measuring cloud. present results obtained numerical renormalization group for wide range physically accessible parameters.

The effect of a magnetic field on the equilibrium spectral and transport properties single-molecule junction is studied using numerical renormalization group method. molecule described by Anderson-Holstein model in which single vibrational mode coupled to electron density. an applied conductance Kondo regime qualitatively different weak strong electron-phonon coupling regimes. In former case, resonance split strongly suppressed...

The low-temperature transport properties of a molecule are studied in the field-effect transitor geometry. has an internal mechanical mode that modulates its electronic levels and renormalizes both interactions coupling to electrodes. For soft mode, spin fluctuations dominated by bare couplings, while valence changes determined dressed energies. In this case, present anomalous behavior Kondo temperature weak gate voltage dependence. These observations agreement with recent experimental data.

We investigate the effect of mass imbalance in binary Fermi mixtures loaded optical lattices. Using dynamical mean-field theory, we study transition from a fluid to Mott insulator driven by repulsive interactions. For almost every value parameters find that light species with smaller bare is more affected correlations than heavy one, so their effective masses become closer before occurs. The strength critical repulsion decreases monotonically as grows minimum realized when one localized....

We study the charge and spin Seebeck effects in a spin-1 molecular junction as function of temperature (T), applied magnetic field (H), anisotropy (D) using Wilson's numerical renormalization group. A hard-axis produces large enhancement coefficient Sc (\sim k_B/|e|) whose value only depends on residual interaction between quasiparticles low Fermi-liquid regime. In underscreened Kondo regime, high sensitivity system to fields makes it possible observe sizable for even much smaller than...

The zero-temperature core-level photoemission spectrum of a Hubbard system is studied across the metal to Mott insulator transition using dynamical mean-field theory and Wilson's numerical renormalization group [Rev. Mod. Phys. 47, 773 (1975)]. An asymmetric power-law divergence obtained in metallic phase with an exponent $\ensuremath{\alpha}(U,Q)\ensuremath{-}1$, which depends on strength both interaction $U$ core-hole potential $Q$. For $Q\ensuremath{\lesssim}{U}_{c}∕2$,...

We introduce a valence bond dynamical mean-field theory of doped Mott insulators. It is based on minimal cluster two orbitals, each associated with different region momentum space and hybridized to self-consistent bath. The low-doping regime characterized by singlet formation the suppression quasiparticles in antinodal regions, leading Fermi arcs. This described terms an orbital-selective transition reciprocal space. calculated tunneling photoemission spectra are consistent phenomenology...

We report low-temperature transport measurements through a double quantum dot device in configuration where one of the dots is coupled directly to source and drain electrodes, second (side-coupled) interacts electrostatically via tunneling first one. As interdot coupling increases, crossover from weak strong observed charge stability diagrams that present complex pattern with mergings apparent crossings Coulomb blockade peaks. While regime can be understood by considering single level on...

We analyze the electronic transport through a model spin-1 molecule as function of temperature, magnetic field and bias voltage. consider effect anisotropy, which can be generated experimentally by stretching molecule. In relevant regime conductance unstretched reaches unitary limit underscreened spin- 1 Kondo at low temperatures. The anisotropy generates an antiferromagnetic coupling between remaining spin 1/2 singular density quasiparticles, producing second reduced conductance. results...

We analyze the transport properties of a double quantum dot device in side-coupled configuration. A small (QD), having single relevant electronic level, is coupled to source and drain electrodes. larger QD, whose multilevel nature considered, tunnel-coupled QD. Fermi liquid analysis shows that low temperature conductance determined by total occupation When Kondo regime, an even number electrons large leads reaches unitary limit, while for odd two stage effect observed strongly suppressed....

The discovery in 2001 of superconductivity some heavy fermion compounds the RMIn$_5$ (R=4f or 5f elements, M=Co, Rh, Ir) family, has triggered enormous amount research pointing to understand physical origin and its relation with magnetism. Although many properties have been clarified, there are still crutial questions that remain unanswered. One these is particular role transition metal determining value critical superconducting temperature (Tc). In this work, we analyse an interesting...

The interplay of electron-electron and electron-phonon interactions is studied analytically in the Kondo regime. A Holstein coupling shown to produce a weakening gate voltage dependence temperature may explain observed anomalies some these devices. molecular center-of-mass mode opens new channel for charge spin fluctuations antiadabatic limit latter are described by an asymmetric two-channel model. Below system develops dynamical Jahn-Teller distortion low energy peak emerges phonon spectral...