We study the Kondo effect in a quantum dot subject to an external ac field. The Kondo effect can be probed by measuring the dc current induced by an auxiliary dc bias Vdc applied across the dot. In the absence of ac perturbation, the corresponding differential conductance G(Vdc) is known to exhibit a sharp peak at Vdc50, which is the manifestation of the Kondo effect. There exists only one ener...

The influence of high-frequency fields on quantum transport through a quantum dot is studied in the low-temperature regime. We generalize the non crossing approximation for the infinite-U Anderson model to the timedependent case. The dc spectral density shows asymmetric Kondo side peaks due to photon-assisted resonant tunneling. As a consequence we predict an electron-photon pump at zero bias w...

Gastgeber: Prof. Gisela Schütz, Max-Planck-Institut für Intelligente Systeme, Telefon: 0711 689-1950 Strongly interacting electrons: from Kondo effect to quantum criticality Hilbert von Löhneysen Karlsruhe Institute of Technology (KIT) Physikalisches Institut und Institut für Festkörperphysik About 50 years ago, Jun Kondo explained a phenomenon in solid-state physics that at that time had been ...

– We present results for a model that describes a quantum point contact. We show how electron-electron correlations, within the unrestricted Hartree-Fock approximation, generate a magnetic moment in the point contact. Having characterized the magnetic structure of the contact, we map the problem onto a simple one-channel model and calculate the temperature dependence of the conductance for diff...

We review our recent studies on the Kondo effect in the tunneling phenomena through quantum dot systems. Numerical methods to calculate reliable tunneling conductance are developed. In the first place, a case in which electrons of odd number occupy the dot is studied, and experimental results are analyzed based on the calculated result. Tunneling anomaly in the even-number-electron occupation c...

We report results of low-temperature thermodynamic and transport measurements of Pb1-xTlxTe single crystals for Tl concentrations up to the solubility limit of approximately x=1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effec...

We investigate adiabatic pumping through a quantum dot with a single level in the mixed-valence and Kondo regimes using the slave boson mean field approximation. The pumped current is driven by a gauge potential due to time-dependent tunneling barriers as well as by the modulation of the Friedel phase. The sign of the former contribution depends on the strength of the Coulomb interaction. Under...

We give a brief review of the Kondo effect and exactly solve the nonequilibrium Kondo problem at the special point in the parameter space of the model with spin-dependent chemical potentials. Using the obtained solution, we compute several experimentally observable quantities: charge current, spin current and magnetic properties. Applications to the physically important cases such as the case w...

R eal metals invariably contain impurity atoms, and at concentrations of parts per million, nonmagnetic impurities have a barely detectable influence on the electronic properties of the vast majority of metals. On the other hand, pronounced changes can arise from magnetic impurities, such as iron impurity atoms in gold. At room temperature the magnetic moment carried by iron’s 3d electrons is d...