Transport across two interacting quantum dots: Bulk Kondo, Kondo box, and molecular regimes

We analyze the transport properties of a double quantum dot device with both dots coupled to perfect conducting leads and to a finite chain of N noninteracting sites connecting both of them. The interdot chain strongly influences the transport across the system and the local density of states of the dots. We study the case of a small number of sites, so that Kondo box effects are present, varying the coupling between the dots and the chain. For odd N and small coupling between the interdot chain and the dots, a state with two coexisting Kondo regimes develops: the bulk Kondo due to the quantum dots connected to leads and the one produced by the screening of the quantum dot spins by the spin in the finite chain at the Fermi level. As the coupling to the interdot chain increases, there is a crossover to a molecular Kondo effect, due to the screening of the molecule (formed by the finite chain and the quantum dots) spin by the leads. For even N the two Kondo temperatures regime does not develop and the physics is dominated by the usual competition between Kondo and antiferromagnetism between the quantum dots. We finally study how the transport properties are affected as N is increased. For the study we used exact multiconfigurational Lanczos calculations and finite-U slave-boson mean-field theory at T=0. The results obtained with both methods describe qualitatively and also quantitatively the same physics.We acknowledge financial support from the Brazilian agencies FAPERJ (CNE) and CNPq, the Spanish MCYT (Grants No. FIS2009-10325 and No. FIS2012-35880), CONICET (Argentina), Universidad de Alicante, and PUC–Rio de Janeiro

A model for predicting the Ms temperatures of steels.

Using neural networks in a Bayesian framework, a model has been derived for the Ms temperature of steels over a wide range of compositions. By its design and by use of a more extensive database, this model improves over existing ones, by its accuracy and its ability to avoid wild predictions.NPL for provision of MTDATA and Neuromat for provision of the Model Manager.Peer reviewe

Chapter One - Inelastic electron excitation of transition metal atoms and Kondo resonances

An ionic Hamiltonian based on the first Hund rule applied to transition metal atoms is reviewed and discussed in detail. The tunneling current between a STM-tip and a transition metal atom is analyzed by means of that Hamiltonian combined with an effective crystal-field effect. We use an equation of motion (EOM) method to calculate that inelastic tunneling current, as well as the Kondo resonance appearing at the Fermi level. We show how an accurate description of its Kondo resonance for the Co/Cu2N(100) system can be achieved by extending the EOM-calculation up to fourth-order in the atom/metal interaction that defines the parameter of expansion in the EOM-equations. These results allow us to calculate also the inelastic tunneling excitation of the atom and the dynamical fluctuations of the atomic spin from S = 3/2 to S = 1.E.C.G. acknowledges financial support by CONICET through Grant No. PIP-201101-00621 and U.N.L. through CAI+D grants. F.F. acknowledges support from the Spanish Ministerio de Economía y Competitividad (MINECO) under project MAT2014-59966-R. and through the “María de Maeztu” Programme for Units of Excellence in R&D (MDM-2014-0377). E.V.A. acknowledges financial support of the Brazilian Agency CNPQ under Project no 306000/2017-2. G.Ch. acknowledges financial support of Ministerio de Ciencia y Educación under project FIS2015-G4222-C2-2-P