Results for "Rok Žitko"

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A Strange Metal from Gutzwiller correlations in infinite dimensions II: Transverse Transport, Optical Response and Rise of Two Relaxation RatesMay 04 2017Jul 05 2017Using two approaches to strongly correlated systems, the extremely correlated Fermi liquid theory and the dynamical mean field theory, we compute the transverse transport coefficients, namely the Hall constants $R_H$ and Hall angles $\theta_H$, and also ... More
Interplay between Yu-Shiba-Rusinov states and spin-flip excitations on magnetic impurities on superconducting NbSe$_2$ substrateNov 28 2018Exchange coupling between a magnetic impurity and a superconducting substrate results in the formation of Yu-Shiba-Rusinov (YSR) bound states, which have been recently used in artificial designer structures to realize exotic quasiparticles known as Majorana ... More
Fine structure of the spectra of the Kondo lattice model: two-site cellular DMFT studyDec 06 2016We study the antiferromagnetic and the paramagnetic Kondo insulator phases of the Kondo lattice model on the cubic lattice at half-filling using the cellular dynamical mean-field theory (CDMFT) with numerical renormalization group (NRG) as the impurity ... More
Padé approximants for improved finite-temperature spectral functions in the numerical renormalization groupFeb 14 2013We introduce an improved approach for obtaining smooth finite-temperature spectral functions of quantum impurity models using the numerical renormalization group (NRG) technique. It is based on calculating first the Green's function on the imaginary-frequency ... More
Tunable Kondo effect in double quantum dots coupled to ferromagnetic contactsOct 26 2011Oct 27 2011We investigate the effects induced by spin polarization in the contacts attached to a serial double quantum dot. The polarization generates effective magnetic fields and suppresses the Kondo effect in each dot. The super-exchange interaction ($J_{\mathrm{AFM}}$), ... More
Transport and Optical Conductivity in the Hubbard Model: A High-Temperature Expansion PerspectiveAug 04 2016We derive analytical expressions for the spectral moments of the dynamical response functions of the Hubbard model using the high-temperature series expansion. We consider generic dimension $d$ as well as the infinite-$d$ limit, arbitrary electron density ... More
Non-Fermi-liquid behavior in quantum impurity models with superconducting channelsJun 24 2016We study how the non-Fermi-liquid nature of the overscreened multi-channel Kondo impurity model affects the response to a BCS pairing term that, in the absence of the impurity, opens a gap $\Delta$. We find that non-Fermi liquid features do persist even ... More
Cesium bright matter-wave solitons and soliton trainsFeb 08 2019Mar 05 2019A study of bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is investigated. Formation of soliton trains ... More
Mottness collapse without metallisation in the domain walls of triangular-lattice Mott insulator 1T-TaS$_2$Oct 22 20181T-TaS$_2$ is a charge-density-wave (CDW) compound with a Mott-insulating ground state. The metallic state obtained by doping, substitution or pulsed charge injection is characterized by an emergent CDW domain wall network, while single domain walls can ... More
Nanostructured and Modulated Low-Dimensional SystemsMar 26 2013Charge density wave (CDW) ordering in NbSe3 and the structurally related quasi one-dimensional compounds is reconsidered. Since the modulated ground state is characterized by unstable nano-domains, the structural information obtained from diffraction ... More
Transport and Optical Conductivity in the Hubbard Model: A High-Temperature Expansion PerspectiveAug 04 2016Nov 10 2016We derive analytical expressions for the spectral moments of the dynamical response functions of the Hubbard model using the high-temperature series expansion. We consider generic dimension $d$ as well as the infinite-$d$ limit, arbitrary electron density ... More
A Strange Metal from Gutzwiller correlations in infinite dimensionsMar 07 2017Aug 18 2017Recent progress in extremely correlated Fermi liquid theory (ECFL) and dynamical mean field theory (DMFT) enables us to compute in the $d \to \infty$ limit the resistivity of the $t-J$ model after setting $J\to0$. This is also the $U=\infty$ Hubbard model. ... More
Non-Drude universal scaling laws for the optical response of local Fermi liquidsDec 26 2012Mar 07 2013We investigate the frequency and temperature dependence of the low-energy electron dynamics in a Landau Fermi liquid with a local self-energy. We show that the frequency and temperature dependencies of the optical conductivity obey universal scaling forms, ... More
Outerstring graphs are $χ$-boundedDec 05 2013Feb 03 2016An outerstring graph is an intersection graph of curves lying in a halfplane with one endpoint on the boundary of the halfplane. It is proved that the outerstring graphs are $\chi$-bounded, that is, their chromatic number is bounded by a function of their ... More
Quantum impurity coupled to Majorana edge fermionsAug 31 2011Oct 20 2011We study a quantum impurity coupled to the edge states of a two-dimensional helical topological superconductor, i.e., to a pair of counterpropagating Majorana fermion edge channels with opposite spin polarizations. For an impurity described by the Anderson ... More
Cesium bright matter-wave solitons and soliton trainsFeb 08 2019A setup for studying bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is studied. Formation of soliton ... More
Non-perturbative effects and indirect exchange interaction between quantum impurities on metallic (111) surfacesNov 21 2016Nov 28 2016The (111) surface of noble metals is usually treated as an isolated two dimensional (2D) triangular lattice completely decoupled from the bulk. However, unlike topological insulators, other bulk bands cross the Fermi level. We here introduce an effective ... More
Inferring the dynamics of oscillatory systems using recurrent neural networksApr 04 2019We investigate the predictive power of recurrent neural networks for oscillatory systems not only on the attractor, but in its vicinity as well. For this we consider systems perturbed by an external force. This allows us to not merely predict the time ... More
Outerstring graphs are $χ$-boundedDec 05 2013Dec 02 2018An outerstring graph is an intersection graph of curves that lie in a common half-plane and have one endpoint on the boundary of that half-plane. We prove that the class of outerstring graphs is $\chi$-bounded, which means that their chromatic number ... More
Smallest tetravalent half-arc-transitive graphs with the vertex-stabiliser isomorphic to the dihedral group of order $8$Dec 01 2014Mar 13 2015A connected graph whose automorphism group acts transitively on the edges and vertices, but not on the set of ordered pairs of adjacent vertices of the graph is called half-arc-transitive. It is well known that the valence of a half-arc-transitive graph ... More
Non-perturbative effects and indirect exchange interaction between quantum impurities on metallic (111) surfacesNov 21 2016The (111) surface of noble metals is usually treated as an isolated two dimensional (2D) triangular lattice completely decoupled from the bulk. However, unlike topological insulators, other bulk bands cross the Fermi level. We here introduce an effective ... More
Coloring curves that cross a fixed curveDec 18 2015Aug 04 2016We prove that for every integer $t\geq 1$, the class of intersection graphs of curves in the plane each of which crosses a fixed curve in at least one and at most $t$ points is $\chi$-bounded. As a corollary, we prove that for any integers $k\geq 2$ and ... More
Coloring curves that cross a fixed curveDec 18 2015Oct 04 2017We prove that for every integer $t\geq 1$, the class of intersection graphs of curves in the plane each of which crosses a fixed curve in at least one and at most $t$ points is $\chi$-bounded. This is essentially the strongest $\chi$-boundedness result ... More
Validation of a Control Algorithm for Human-like Reaching Motion using 7-DOF Arm and 19-DOF Hand-Arm SystemsNov 05 2013This technical report gives an overview of our work on control algorithms dealing with redundant robot systems for achieving human-like motion characteristics. Previously, we developed a novel control law to exhibit human-motion characteristics in redundant ... More
Non-linear Task-Space Disturbance Observer for Position Regulation of Redundant Robot Arms against Perturbations in 3D EnvironmentsNov 02 2013Many day-to-day activities require the dexterous manipulation of a redundant humanoid arm in complex 3D environments. However, position regulation of such robot arm systems becomes very difficult in presence of non-linear uncertainties in the system. ... More
Ontology-based multi-agent system to support business users and managementJul 10 2018For some decision processes a significant added value is achieved when enterprises' internal Data Warehouse (DW) can be integrated and combined with external data gained from web sites of competitors and other relevant Web sources. In this paper we discuss ... More
Conflict-Free Coloring of String GraphsDec 12 2017Jan 18 2019Conflict-free coloring (in short, CF-coloring) of a graph $G = (V,E)$ is a coloring of $V$ such that the neighborhood of each vertex contains a vertex whose color differs from the color of any other vertex in that neighborhood. Bounds on CF-chromatic ... More
Spin-orbit coupling in three-orbital Kanamori impurity model and its relevance for transition-metal oxidesAug 21 2017We investigate the effects of the spin-orbit coupling (SOC) in a three-orbital impurity model with Kanamori interaction using the numerical renormalization group method. We focus on the impurity occupancy $N_d=2$ relevant to the dynamical mean-field theory ... More
Low-energy physics of three-orbital impurity model with Kanamori interactionJun 24 2016We discuss the low-energy physics of the three-orbital Anderson impurity model with the Coulomb interaction term of the Kanamori form which has orbital SO(3) and spin SU(2) symmetry and describes systems with partially occupied $t_{2g}$ shells. We focus ... More
Superconducting quantum dot and the sub-gap statesJan 04 2019Quantum dots are nanostructures made of semiconducting materials that are engineered to hold a small amount of electric charge (a few electrons) that is controlled by external gate and may hence be considered as tunable artificial atoms. A quantum dot ... More
Historical observations of STEVEJul 23 2018Recent work by MacDonald et al. has highlighted the valuable work carried out by sky watchers and auroral enthusiasts in obtaining high-quality digital images of rare and unusual auroral structures. A feature of particular interest, which has been nicknamed ... More
CASC: Context-Aware Segmentation and Clustering for Motif Discovery in Noisy Time Series DataSep 06 2018Complex systems, such as airplanes, cars, or financial markets, produce multivariate time series data consisting of system observations over a period of time. Such data can be interpreted as a sequence of segments, where each segment is associated with ... More
Charge density wave ordering in NbSe3: possible models and the experimental evidenceApr 15 2010Charge density wave (CDW) ordering in the prototypical low-dimensional compound NbSe3 is reconsidered. We show that the widely accepted CDW model with two incommensurate modulations, q1 = (0,0.241,0) and q2 = (0.5,0.260,0.5), localized on type-III and ... More
Spectral properties of Shiba sub-gap states at finite temperaturesJan 19 2016Using the numerical renormalization group (NRG), we analyze the temperature dependence of the spectral function of a magnetic impurity described by the single-impurity Anderson model coupled to superconducting contacts. With increasing temperature the ... More
Kondo resonance line-shape of magnetic adatoms on decoupling layersOct 20 2011Oct 24 2011The zero-bias resonance in the dI/dV tunneling spectrum recorded using a scanning tunneling microscope above a spin-1/2 magnetic adatom (such as Ti) adsorbed on a decoupling layer on metal surface can be accurately fitted using the universal spectral ... More
Quantitative determination of the discretization and truncation errors in the numerical renormalization-group calculations of spectral functionsMay 24 2011Aug 09 2011In the numerical renormalization group (NRG) calculations of the spectral functions of quantum impurity models, the results are affected by discretization and truncation errors. The discretization errors can be alleviated by averaging over different discretization ... More
Kondo screening in high-spin side-coupled two-impurity clustersNov 11 2009We study the system of two magnetic impurities described by a two-impurity Kondo model where only the first impurity couples directly to the conduction band, while the second impurity interacts with the first through Heisenberg exchange coupling in a ... More
Spin-thermopower in interacting quantum dotsSep 14 2011Feb 16 2012Using analytical arguments and the numerical renormalization group method we investigate the spin-thermopower of a quantum dot in a magnetic field. In the particle-hole symmetric situation the temperature difference applied across the dot drives a pure ... More
Fano-Kondo effect in side-coupled double quantum dots at finite temperatures and the importance of the two-stage Kondo screeningJan 12 2010Mar 04 2010We study the zero-bias conductance through the system of two quantum dots, one of which is embedded directly between the source and drain electrodes, while the second dot is side-coupled to the first one through a tunneling junction. Modeling the system ... More
Convergence acceleration and stabilization for dynamical-mean-field-theory calculationsAug 05 2009The convergence to the self-consistency in the dynamical-mean-field-theory (DMFT) calculations for models of correlated electron systems can be significantly accelerated by using an appropriate mixing of hybridization functions which are used as the input ... More
Magnetic impurities in spin-split superconductorsNov 25 2016Hybrid semiconductor-superconductor quantum dot devices are tunable physical realizations of quantum impurity models for a magnetic impurity in a superconducting host. The binding energy of the localized sub-gap Shiba states is set by the gate voltages ... More
Quantum impurity on the surface of a topological insulatorMar 29 2010Feb 04 2011It is shown that the Hamiltonian for a quantum magnetic impurity on the surface of a topological insulator can be mapped to the conventional pseudo-gap Anderson impurity model, albeit with the combinations of continuum states which hybridize with the ... More
NRG calculations of the ground-state energy: application to the correlation effects in the adsorption of magnetic impurities on metal surfacesAug 05 2009The ground-state energy of a quantum impurity model can be calculated using the numerical renormalization group with a modified discretization scheme, with sufficient accuracy to reliably extract physical information about the system. The approach is ... More
Numerical sub-gap spectroscopy of double quantum dots coupled to superconductorsDec 22 2014Apr 03 2015Double quantum dot nanostructures embedded between two superconducting leads or in a superconducting ring have complex excitation spectra inside the gap which reveal the competition between different many-body phenomena. We study the corresponding two-impurity ... More
Hydrogenation Properties of the TiBx StructuresJul 30 2011Titanium borates show promissing hydrogen storage characteristics. Structural relaxation around individual hydrogen atoms and the binding energies are studied by means of the density functional theory methods for a number of hydrogenated TiB2, TiB and ... More
Supercurrent in a double quantum dotAug 17 2018Oct 15 2018We demonstrate the Josephson effect in a serial double quantum dot defined in a nanowire with epitaxial superconducting leads. The supercurrent stability diagram adopts a honeycomb pattern with electron-hole and left-right reflection symmetry. We observe ... More
Adaptive logarithmic discretization for numerical renormalization group methodsFeb 18 2009Feb 20 2009The problem of the logarithmic discretization of an arbitrary positive function (such as the density of states) is studied in general terms. Logarithmic discretization has arbitrary high resolution around some chosen point (such as Fermi level) and it ... More
SNEG - Mathematica package for symbolic calculations with second-quantization-operator expressionsMay 24 2011In many-particle problems involving interacting fermions or bosons, the most natural language for expressing the Hamiltonian, the observables, and the basis states is the language of the second-quantization operators. It thus appears advantageous to write ... More
Detection of Majorana edge states in topological superconductors through the non-Fermi-liquid effects induced in an interacting quantum dotFeb 04 2011May 24 2011It is shown that the presence of the Majorana fermion edge states along the perimeter of a topological superconductor can be probed using an interacting quantum dot coupled to three terminals: two spin-polarized (ferromagnetic) leads and one lead supporting ... More
A Systematic Look at the Effects of Radiative Feedback on Disc Galaxy FormationAug 28 2013Sep 01 2014Galaxy formation models and simulations rely on various feedback mechanisms to reproduce the observed baryonic scaling relations and galaxy morphologies. Although dwarf galaxy and giant elliptical properties can be explained using feedback from supernova ... More
Shiba states and zero-bias anomalies in the hybrid normal-superconductor Anderson modelMay 23 2014Feb 02 2015We determine the phase diagram of an Anderson impurity in contact with superconducting and normal-state leads for arbitrary ratio of the gap $\Delta$ to the Kondo temperature $T_K$. We observe a considerable effect of even very weak coupling to the normal ... More
Two-Impurity Yu-Shiba-Rusinov States in Coupled Quantum DotsDec 21 2018Using Coulomb blockaded double quantum dots, we realize the superconducting analog of the celebrated two-impurity Kondo model. Focusing on gate regions with a single spin-1/2 on each dot, we demonstrate gate-tuned changes of the ground state from an interdot ... More
Field-Induced Instability of a Gapless Spin Liquid with a Spinon Fermi SurfaceSep 07 2017Oct 02 2017The ground state of the quantum kagome antiferromagnet Zn-brochantite, ZnCu$_3$(OH)$_6$SO$_4$, which is one of only a few known spin-liquid (SL) realizations in two or three dimensions, has been described as a gapless SL with a spinon Fermi surface. Employing ... More
Kondo screening in a charge-insulating spinon metalApr 13 2019The Kondo effect, an eminent manifestation of many-body physics in condensed matter, is traditionally explained as exchange scattering of conduction electrons on a spinful impurity in a metal. The resulting screening of the impurity's local moment by ... More
Enhanced Conductance Through Side-Coupled Double Quantum DotsOct 20 2005Conductance, on-site and inter-site charge fluctuations and spin correlations in the system of two side-coupled quantum dots are calculated using the Wilson's numerical renormalization group (NRG) technique. We also show spectral density calculated using ... More
A short proof of the first selection lemma and weak $\frac{1}{r}$-nets for moving pointsDec 23 2015(i) We provide a short and simple proof of the first selection lemma. (ii) We also prove a selection lemma of a new type in $\Re^d$. For example, when $d=2$ assuming $n$ is large enough we prove that for any set $P$ of $n$ points in general position there ... More
Anomaly in the heat capacity of Kondo superconductorsNov 09 2008Nov 12 2008Using numerical renormalization group we study thermodynamic properties of a magnetic impurity described by the Anderson impurity model in a superconducting host material described by the BCS Hamiltonian. When the Kondo temperature in the normal state, ... More
Monotonicity of Fitness Landscapes and Mutation Rate ControlSep 04 2012The typical view in evolutionary biology is that mutation rates are minimised. Contrary to that view, studies in combinatorial optimisation and search have shown a clear advantage of using variable mutation rates as a control parameter to optimise the ... More
Vertex corrections to the optical conductivity in the square lattice Hubbard model and their role for the high-temperature transportNov 20 2018Calculating transport properties presents a great challenge in the study of strongly correlated electrons, particularly in two dimensions where the non-local processes and the vertex corrections are important, but remain poorly understood. We study the ... More
Driver Identification Using Automobile Sensor Data from a Single TurnJun 09 2017As automotive electronics continue to advance, cars are becoming more and more reliant on sensors to perform everyday driving operations. These sensors are omnipresent and help the car navigate, reduce accidents, and provide comfortable rides. However, ... More
Scaling of sub-gap excitations in a superconductor-semiconductor nanowire quantum dotSep 24 2016A quantum dot coupled to a superconducting contact provides a tunable artificial analogue of a magnetic atom in a superconductor, a paradigmatic quantum impurity problem. We realize such a system with an InAs semiconductor nanowire contacted by an Al-based ... More
A Thickness Dependent Enhancement of Optical Resolution in the Vicinity of an Epsilon-near-zero SlabMay 23 2016Recent studies reports that an epsilon-near-zero (ENZ) thin slab between a specimen and a substrate contributes in enhancing the spatial resolution of the optical system. Here, we investigate the ENZ thickness dependence of the resolution enhancement. ... More
Memristor MOS Content Addressable Memory (MCAM): Hybrid Architecture for Future High Performance Search EnginesMay 11 2010Large-capacity Content Addressable Memory (CAM) is a key element in a wide variety of applications. The inevitable complexities of scaling MOS transistors introduce a major challenge in the realization of such systems. Convergence of disparate technologies, ... More
SNAP: A General Purpose Network Analysis and Graph Mining LibraryJun 24 2016Large networks are becoming a widely used abstraction for studying complex systems in a broad set of disciplines, ranging from social network analysis to molecular biology and neuroscience. Despite an increasing need to analyze and manipulate large networks, ... More
Energy resolution and discretization artefacts in the numerical renormalization groupOct 27 2008Nov 05 2008We study the limits of the energy resolution that can be achieved in the calculations of spectral functions of quantum impurity models using the numerical renormalization group (NRG) technique with interleaving (z-averaging). We show that overbroadening ... More
Quantum phase transitions in the systems of parallel quantum dotsNov 30 2007We study the low-temperature transport properties of the systems of parallel quantum dots described by the N-impurity Anderson model. We calculate the quasiparticle scattering phase shifts, spectral functions and correlations as a function of the gate ... More
The Two-impurity Anderson Model Revisited: Competition between Kondo Effect and Reservoir-mediated Superexchange in Double Quantum DotsNov 05 2009We study a series-coupled double quantum dot in the Kondo regime modeled by the two-impurity Anderson model and find a new conduction-band mediated superexchange interaction that competes with Kondo physics in the strong Coulomb interaction limit. Our ... More
An Analytical Approach for Memristive NanoarchitecturesJun 15 2011Dec 13 2011As conventional memory technologies are challenged by their technological physical limits, emerging technologies driven by novel materials are becoming an attractive option for future memory architectures. Among these technologies, Resistive Memories ... More
Tunneling through an Aharonov-Bohm ring -- effects of dephasing by electron-electron interactionsJul 12 2002We develop a non-perturbative numerical method to study a single electron tunneling through an Aharonov-Bohm ring in the presence of bound, interacting electrons. Inelastic processes and spin-flip scattering are properly taken into account. We show that ... More
Inferring the phase response curve from observation of a continuously perturbed oscillatorFeb 28 2018Sep 18 2018Phase response curves are important for analysis and modeling of oscillatory dynamics in various applications, particularly in neuroscience. Standard experimental technique for determining them requires isolation of the system and application of a specifically ... More
Link prediction in Foursquare networkFeb 11 2016Foursquare is an online social network and can be represented with a bipartite network of users and venues. A user-venue pair is connected if a user has checked-in at that venue. In the case of Foursquare, network analysis techniques can be used to enhance ... More
The Kondo effect in the presence of the Rashba spin-orbit interactionOct 20 2011We study the temperature scale of the Kondo screening of a magnetic impurity which hybridizes with a two-dimensional electron gas in the presence of the Rashba spin-orbit interaction. The problem is mapped to an effective single-band impurity model with ... More
Fermi-liquid versus non-Fermi-liquid behavior in triple quantum dotsJun 12 2006Dec 15 2006We study the effect of electron hopping in triple quantum dots modelled by the three-impurity Anderson model. We determine the range of hopping parameters where the system exhibits the two-channel Kondo effect and has non-Fermi-liquid properties in a ... More
Direct formation of supermassive black holes in metal-enriched gas at the heart of high-redshift galaxy mergersNov 20 2014We present novel 3D multi-scale SPH simulations of gas-rich galaxy mergers between the most massive galaxies at $z \sim 8 - 10$, designed to scrutinize the direct collapse formation scenario for massive black hole seeds proposed in \citet{mayer+10}. The ... More
Non-volatile Complementary Resistive Switch-based Content Addressable MemoryAug 18 2011Oct 16 2011This paper presents a novel resistive-only Binary and Ternary Content Addressable Memory (B/TCAM) cell that consists of two Complementary Resistive Switches (CRSs). The operation of such a cell relies on a logic$\rightarrow$ON state transition that enables ... More
Electrical Investigation of the Oblique Hanle Effect in Ferromagnet/Oxide/Semiconductor ContactsNov 15 2012Jan 09 2013We have investigated the electrical Hanle effect with magnetic fields applied at an oblique angle ({\theta}) to the spin direction (the oblique Hanle effect, OHE) in CoFe/MgO/semiconductor (SC) contacts by employing a three-terminal measurement scheme. ... More
Josephson current in strongly correlated double quantum dotsFeb 18 2010We study the transport properties of a serial double quantum dot (DQD) coupled to two superconducting leads, focusing on the Josephson current through the DQD and the associated 0-$\pi$ transitions which result from the subtle interplay between the superconductivity, ... More
SnapVX: A Network-Based Convex Optimization SolverSep 21 2015SnapVX is a high-performance Python solver for convex optimization problems defined on networks. For these problems, it provides a fast and scalable solution with guaranteed global convergence. SnapVX combines the capabilities of two open source software ... More
Reconstructing networks of pulse-coupled oscillators from spike trainsMar 23 2017We present an approach for reconstructing networks of pulse-coupled neuron-like oscillators from passive observation of pulse trains of all nodes. It is assumed that units are described by their phase response curves and that their phases are instantaneously ... More
$Z_2$-gauge theory description of the Mott transition in infinite dimensionsApr 07 2015The infinite dimensional half-filled Hubbard model can be mapped exactly with no additional constraint onto a model of free fermions coupled in a $Z_2$ gauge-invariant manner to auxiliary Ising spins in a transverse field. In this slave-spin representation, ... More
Spin-charge separation and simultaneous spin and charge Kondo effectDec 15 2006We study the spin-charge separation in a Kondo-like model for an impurity with a spin and a charge (isospin) degree of freedom coupled to a single conduction channel (the ``spin-charge'' Kondo model). We show that the spin and charge Kondo effects can ... More
Correlation Effects in Side-Coupled Quantum DotsMay 31 2007Using Wilson's numerical renormalization group (NRG) technique we compute zero-bias conductance and various correlation functions of a double quantum dot (DQD) system. We present different regimes within a phase diagram of the DQD system. By introducing ... More
Supercurrent through a spin-split quasi-ballistic point contact in an InAs nanowireJan 05 2018We study the superconducting proximity effect in an InAs nanowire contacted by Ta-based superconducting electrodes. Using local bottom gates, we control the potential landscape along the nanowire, tuning its conductance to a quasi-ballistic regime. At ... More
SnapVX: A Network-Based Convex Optimization SolverSep 21 2015Feb 21 2017SnapVX is a high-performance Python solver for convex optimization problems defined on networks. For these problems, it provides a fast and scalable solution with guaranteed global convergence. SnapVX combines the capabilities of two open source software ... More
Numerical renormalization group study of two-channel three-impurity triangular clustersMar 05 2009We study triangular clusters of three spin-1/2 Kondo or Anderson impurities that are coupled to two conduction leads. In the case of Kondo impurities, the model takes the form of an antiferromagnetic Heisenberg ring with Kondo-like exchange coupling to ... More
Lifshitz phase transitions in the ferromagnetic regime of the Kondo lattice modelJan 10 2013Jul 02 2013We establish the low-temperature phase diagrams of the spin-1/2 and spin-1 Kondo lattice models as a function of the conduction-band filling n and the exchange coupling strength J in the regime of ferromagnetic effective exchange interactions (n ~< 0.5). ... More
Many-particle effects in adsorbed magnetic atoms with easy-axis anisotropy: the case of Fe on CuN/Cu(100) surfaceFeb 22 2010Jun 10 2010We study the effects of the exchange interaction between an adsorbed magnetic atom with easy-axis magnetic anisotropy and the conduction-band electrons from the substrate. We model the system using an anisotropic Kondo model and we compute the impurity ... More
Ray-tracing semiclassical low frequency acoustic modeling with local and extended reaction boundariesMay 10 2017The recently introduced acoustic ray-tracing semiclassical (RTS) method is validated for a set of practically relevant boundary conditions. RTS is a frequency domain geometrical method which directly reproduces the acoustic Green's function. As previously ... More
Kondo effect at low electron density and high particle-hole asymmetry in 1D, 2D, and 3DJul 07 2016Sep 06 2016Using the perturbative scaling and the NRG, we study the characteristic energy scales in the Kondo impurity problem as a function of the exchange coupling constant $J$ and the conduction electron density. We discuss the relation between the impurity binding ... More
Ringo: Interactive Graph Analytics on Big-Memory MachinesMar 26 2015We present Ringo, a system for analysis of large graphs. Graphs provide a way to represent and analyze systems of interacting objects (people, proteins, webpages) with edges between the objects denoting interactions (friendships, physical interactions, ... More
How bad metals turn good: spectroscopic signatures of resilient quasiparticlesOct 05 2012Feb 22 2013We investigate transport in strongly correlated metals. Within dynamical mean-field theory, we calculate the resistivity, thermopower, optical conductivity and thermodynamic properties of a hole-doped Mott insulator. Two well-separated temperature scales ... More
A comparative study of nonequilibrium insulator-to-metal transitions in electron-phonon systemsOct 03 2018We study equilibrium and nonequilibrium properties of electron-phonon systems described by the Hubbard-Holstein model using the dynamical mean-field theory. In equilibrium, we benchmark the results for impurity solvers based on the one-crossing approximation ... More
A new high-temperature quantum spin liquid with polaron spinsApr 21 2017The existence of a quantum spin liquid (QSL) in which quantum fluctuations of spins are sufficiently strong to preclude spin ordering down to zero temperature was originally proposed theoretically more than 40 years ago, but its experimental realisation ... More
Abrikosov vortex nucleation and its detrimental effect on superconducting spin pumping in Pt/Nb/Ni80Fe20/Nb/Pt proximity structuresFeb 11 2019Mar 22 2019We report Abrikosov vortex nucleation in Pt/Nb/Ni80Fe20/Nb/Pt proximity-coupled structures under oblique ferromagnetic resonance (FMR) that turns out to be detrimental to superconducting spin pumping. By measuring an out-of-plane field-angle {\theta}H ... More
Stellar and Gaseous Nuclear Disks Observed in Nearby (U)LIRGsJan 28 2014We present near-infrared integral field spectroscopy of the central kiloparsec of 17 nearby luminous and ultra-luminous infrared galaxies undergoing major mergers. These observations were taken with OSIRIS assisted by the Keck I and II Adaptive Optics ... More
Memristor-based Synaptic Networks and Logical Operations Using In-Situ ComputingAug 21 2011We present new computational building blocks based on memristive devices. These blocks, can be used to implement either supervised or unsupervised learning modules. This is achieved using a crosspoint architecture which is an efficient array implementation ... More
Abrikosov vortex nucleation and its detrimental effect on superconducting spin pumping in Pt/Nb/Ni80Fe20/Nb/Pt proximity structuresFeb 11 2019We report Abrikosov vortex nucleation in Pt/Nb/Ni80Fe20/Nb/Pt proximity-coupled structures under oblique ferromagnetic resonance (FMR) that turns out to be detrimental to superconducting spin pumping. By measuring an out-of-plane field-angle {\theta}H ... More
Repulsive vs. attractive Hubbard model: transport properties and spin-lattice relaxation rateDec 15 2014Apr 03 2015We contrast the transport properties (dc resistivity, Seebeck coefficient), optical conductivity, spectral functions, dynamical magnetic susceptibility, and the NMR $1/T_1$ spin-lattice relaxation rate of the repulsive and attractive infinite-dimensional ... More
Vibrational Andreev bound states in magnetic moleculesMay 09 2012We predict the existence of vibrational Andreev bound states in deformable magnetic molecules on superconducting surfaces. We discuss the Anderson impurity model with electron-phonon coupling to a realistic anharmonic vibrational mode that modulates the ... More
Splitting of the Kondo resonance in anisotropic magnetic impurities on surfacesFeb 18 2009Using the numerical renormalization group method, we study the splitting of the Kondo resonance by a magnetic field applied in different directions in the Kondo model for anisotropic magnetic impurities. Several types of magnetic anisotropy are considered: ... More