V. Zlatic

Institute of Physics, Zagreb

Dependence of transport coefficients of the Yb(Rh1−xCox)2Si2 series of alloys on temperature and cobalt concentration is explained by an asymmetric Anderson model which takes into account the exchange scattering of conduction electrons on ytterbium ions and the splitting of 4f states by the crystalline electric field (CEF). The substitution of rhod...

The temperature and doping dependence of transport coefficients of Yb(Rh$_{1-x}$Co$_x$)$_2$Si$_2$ series of alloys is explained by an asymmetric Anderson model which takes into account the exchange scattering of conduction electrons on Ytterbium ions and the splitting of 4$f$-states by the crystalline electric field (CEF). The substitution of rhodi...

We present thermopower measurements on Yb(\(\hbox {Rh}_{1-x}\hbox {Co}_x\))\(_2\hbox {Si}_2\). Upon cobalt substitution, the Kondo temperature is decreasing and the single large thermopower minimum observed for \(\hbox {YbRh}_2\hbox {Si}_2\) splits into two minima. Simultaneously, the absolute thermopower values are strongly reduced due to a weaker...

We present thermopower measurements on Yb(Rh$_{1-x}$Co$_x$)$_2$Si$_2$. Upon Co substitution the Kondo temperature is decreasing and the single large thermopower minimum observed for YbRh$_2$Si$_2$ splits into two minima. Simultaneously, the absolute thermopower values are strongly reduced due to a weaker exchange coupling between the $4f$ and the c...

The book contains abstracts from research workshop on Spin, Charge and Energy Transport in Novel Materials, which was held in Hvar, Croatia, in 2017. The workshop addresses the properties of materials that are currently at the forefront of materials science. It includes materials for spintronic, spincaloritronic, magneto- and electrocaloric devices...

The phenomenological textbook equations for charge and heat transport are extensively used in a number of fields ranging from semiconductor devices to thermoelectricity. We provide a rigorous derivation of transport equations by solving the Boltzmann equation in the relaxation-time approximation and show that the currents can be rigorously represen...

We present a theory for charge and heat transport parallel to the interfaces of a multilayer (ML) in which the interfacing gives rise the redistribution of the electronic charges. The ensuing electrical field couples self-consistently to the itinerant electrons, so that the properties of the ML crucially depend on an interplay between the on-site C...

The effect of correlated hopping on the charge and heat transport of strongly correlated particles is studied for the Falicov-Kimball model on the Bethe lattice. An exact solutions for the one particle density of states (DOS) and the two particle transport function (the "quasiparticle" scattering time) are derived using the dynamical mean field the...

We rigorously derive the phenomenological textbook equations for the charge and heat transport starting from the Boltzmann equation in the relaxation time approximation. Our derivation also exposes some limitations of these textbook equations which might become relevant for ever smaller devices. Already to linear order in the driving forces, i.e.,...

This book provides a comprehensive discussion of charge and heat transport in solids, both on the phenomenological and the microscopic level. In the part on phenomenology, based on Onsager’s original approach, conjugate current densities and forces are derived from the condition that the rate of change of the entropy density of the system in the st...

Bad metals display transport behavior that differs from what is commonly seen in ordinary metals. One of the most significant differences is a resistivity that is linear in temperature and rises to well above the Ioffe-Regel limit (where the mean-free path is equal to the lattice spacing). Using an exact Kubo formula, we show that a linear resistiv...

"Bad metals" have a large linear resistivity at high-T that is universally seen in oxides close to the Mott-Hubbard insulating phase. They also have an universal thermopower alpha(T): (i) at very low doping (lightly doped) alpha(T) has a pronounced low-T peak that shifts to higher-T with doping; (ii) at moderate doping (underdoped) alpha(T) has a s...

We investigate the thermoelectric properties of PbTe doped with a small concentration x of Tl impurities acting as acceptors and described by Anderson impurities with negative on-site correlation energy. The resulting charge Kondo effect naturally accounts for a number of the low temperature anomalies in this system, including the unusual doping de...

We discuss the charge and heat transport of a ``bad metal'' described by the Falicov-Kimball model near half-filling, using DMFT. For a lightly doped Mott insulator, the exact solution gives transport coefficients of a universal form at low, T<=T0, and high temperatures, T>=Tμ. These characteristic temperatures are such that, for T<=T0, transport i...

Many materials like the cuprates, heavy fermions, and strongly correlated oxides, are non-Fermi liquid ``bad metals'', with linear or quasi-linear resistivity as a function of temperature. The low-energy excitations are quasiparticle-like near the Fermi surface, but their lifetimes are short, so they are not coherent or free-particle-like, as in co...

Alternative Strategies for Thermoelectric Materials Development A.P. Gonzalves, C.Godart.- Thermopower in Correlated Systems B. Sriram Shastry.- Thermoelectric Properties of Correlated Electron Systems Ln3 Pt4Ge6 and LnPt4Ge12 (Ln = Ce, Pr) and Non-Centrosymmetric X2T12P7 (X = Yb, Hf and T = Fe, Co) B. D. White et al.- Thermopower of the Correlated...

We present a theory for the charge and heat transport in a multilayer made of three sets of planes with strongly correlated electrons. The Mott insulator planes make the left and right barrier; a few delta-doped planes which are close to the metal-insulator transition make a conduction channel. In such a device, the currents can only flow parallel...

We show how a lightly doped Mott insulator has hugely enhanced electronic thermal transport at low temperature. It displays universal behavior independent of the interaction strength when the carriers can be treated as nondegenerate fermions and a nonuniversal "crossover" region where the Lorenz number grows to large values, while still maintaining...

A theory of charge and heat transport in inhomogeneous multilayers (ML) with correlated electrons is presented. We consider the device which consists of several strongly correlated metallic planes (channel) sandwiched between two semi-infinite Mott insulators (barriers). A driving field is applied parallel to the ML planes and the gate voltage perp...

The electronic properties and the electron-phonon coupling in La2-xMxCuO4 type compounds are studied within the tight-binding theory. Derived expressions for electron-phonon coupling exhibit clearly the relative importance of various phonon modes. The possible role of the breathing type oxygen vibrations in the electronically driven lattice instabi...

We investigate the properties of PbTe doped with a small concentration x of Tl impurities acting as acceptors and described by Anderson impurities with negative onsite correlation energy. We use the numerical renormalization group method to show that the resulting charge Kondo effect naturally accounts for the unusual low temperature and doping dep...

The book contains abstracts from the NATO Advanced Researche Workshop on New Materials for Thermoelectric Applications: theory and experiment, Hvar 2011, Croatia. The workshop brings together experts from the various fields to share the latest findings and ideas and discuss directions for future work. Several strategies for improving the performanc...

We report the discovery of two consecutive, pressure driven magnetic instabilities in Yb2Pd2Sn. They emerge in a non-Fermi liquid environment at the initial and the final point of a dome-like, single magnetic phase at pressures pc1≈1 GPa and pc2≈4 GPa. This singular behavior of Yb compounds is supposed to result from mutually competing, pressure mo...

We investigate with the aid of numerical renormalization group techniques the thermoelectric properties of a molecular quantum dot described by the negative-U Anderson model. We show that the charge Kondo effect provides a mechanism for enhanced thermoelectric power via a correlation induced asymmetry in the spectral function close to the Fermi lev...

This book contains the abstracts of the Advanced Research Workshop on New Materials for Thermoelectric Applications, held in Hvar, Croatia, in 2010. The workshop focuses on new materials and explores mechanisms that could lead to new thermoelectric devices with an enhanced figure- of-merit. The main topic is heat, charge and spin transport in stron...

We investigate thermoelectric properties of correlated quantum dots and molecules, described by a single level Anderson model coupled to conduction electron leads, by using Wilson's numerical renormalization group method. In the Kondo regime, the thermopower, $S(T)$, exhibits two sign changes, at temperatures $T=T_{1}$ and $T=T_{2}>T_{1}$. We find...

The thermoelectric properties of strongly correlated quantum dots, described by a single level Anderson model coupled to conduction electron leads, is investigated using Wilson's numerical renormalization group method. We calculate the electronic contribution, $K_{\rm e}$, to the thermal conductance, the thermopower, $S$, and the electrical conduct...

CeCu4 In and CeCu4Ga compounds belong to heavy fermion (HF) systems. CeNi4 In and CeNi4Ga seems to be on the border between HF and mixed-valence (MV) states. It has been observed that thermoelectric power (TEP) shows a significant difference between these Cu and Ni-based compounds, whereas thermal conductivity does not reveal such dramatic changes...

This paper reviews the thermoelectric power (TEP) of cerium and ytterbium Kondo systems. We present first the experimental situation regarding the Kondo compounds and describe briefly the intermediate valence (IV) systems. We then define the Kondo temperature T K and summarize the theoretical approaches that explain the behavior of Kondo systems m...

The thermodynamic and transport properties of intermetallic compounds with Ce, Eu, and Yb ions are discussed using the periodic Anderson model with an infinite correlation between f electrons. At high temperatures, these systems exhibit typical features that can be understood in terms of a single-impurity Anderson or Kondo model with Kondo scale TK...

This book contains abstracts of the NATO ARW Workshop on Properties and Applications of Thermoelectric Materials and Conference on Concepts of Electron Correlation held in Hvar, Croatia, in 2008. The workshop addresses new materials and mechanisms that could lead to new thermoelectric and magnetocaloric devices with an enhanced figure-of-merit. The...

The low-temperature transport coefficients of the degenerate periodic SU(N) Anderson model are calculated in the limit of infinite correlation between {\it f} electrons, within the framework of dynamical mean-field theory. We establish the Fermi liquid (FL) laws in the clean limit, taking into account the quasiparticle damping. The latter yields a...

In the first part of these lecture notes we introduce the phenomenological equations for describing the heat and charge transport in thermoelectric samples. We discuss the solution obtained for various boundary conditions that are appropriate for the homogeneous and inhomogeneous thermoelectrics. In the second part we develop the formalism for a li...

In the first part of these lecture notes we introduce the phenomenological equations for describing the heat and charge transport in thermoelectric samples. We discuss the solution obtained for various boundary conditions that are appropriate for the homogeneous and inhomogeneous thermoelectrics. In the second part we develop the formalism for a li...

The cover picture shows a false-color plot of the density of states for a nanostructure consisting of two ideal metallic leads and a few layers of strongly correlated material in between. The picture originates from the article by Freericks and Zlatić [1]. In this work the authors present a novel approach to transport through strongly anisotropic s...

The formalism for a linear-response many-body treatment of the electronic contributions to thermal transport is developed for multilayered nanostructures. By properly determining the local heat-current operator, it is possible to show that the Jonson-Mahan theorem for the bulk can be extended to inhomogeneous problems, so the various thermal-transp...

A new method of calculating the properties of correlated electrons propagting on D-dimensional lattices with ND sites is used to study the analytic properties of the Hubbard model in one and two dimensions. The single-particle self-energy is evaluated in the weak-coupling limit around the Fermi energy, ωF, and momentum, pF, at T = 0. For D = 1, the...

The spinless Falicov-Kimball model is studied by the use of a recently developed projector-based renormalization method (PRM) for many-particle Hamiltonians. The method is used to evaluate static and dynamic quantities of the one-dimensional model at half-filling. To these belong the quasiparticle excitation energy $\tilde{\epsilon}_k$ and the mome...

The zero-temperature spectral properties and Fermi surface (FS) anomalies of hole-doped 2D Hubbard model with anisotropic nearest-neighbor hopping are evaluated using the perturbation theory. The nested sections of the FS, which are always present in the anisotropic model, are found to expand with the strength of Coulomb correlation U. The renormal...

The many-body formalism for dynamical mean-field theory is extended to treat nonequilibrium problems. We illustrate how the formalism works by examining the transient decay of the oscillating current that is driven by a large electric field turned on at time t=0. We show how the Bloch oscillations are quenched by the electron-electron interactions,...

We present a tight-binding electronic theory for the electronic structure in La2CuO4-type compounds, and a simple analytical formula for the electron-phonon coupling which displays the dominant role of breathing-mode type phonons for superconductivity and lattice instabilities. The problem of phonon softening, spin density instability is also analy...

Strongly correlated electron materials are materials where the electron-electron interaction is so strong it is of primary importance in determining how the materials behave. These materials may be tuned to pass through a metal-insulator transition as a function of chemical doping, pressure, or temperature. This tunability of their properties makes...

The evolution of the thermopower S(T) of EuCu2(Ge1-xSi) intermetallics, which is induced by the Si Ge substitution, is explained by the Kondo scattering of conduction electrons on the Eu ions which fluctuate between the magnetic 2+ and non-magnetic 3+ Hund's rule configurations. The Si Ge substitution is equivalent to chemical pressure which modifi...

The pressure-induced changes of the thermoelectrical power of CeRu2Ge2 can be well described within the single-impurity Anderson model. In this model, the experimental values of the crystal-field splittings of the 4f ground state are taken into account and it is assumed that the strong Coulomb repulsion restricts the number of 4f electrons. The cal...

We exactly calculate the non-equilibrium properties of the Falicov-Kimball model in an external electric field by using a recently developed non-equilibrium dynamical mean-field theory formalism [1,2]. In particular, we analyze the time-dependence of the electrical current in cases with different values of the on-site Coulomb interaction, when the...

The formalism for thermal transport in strongly correlated multilayered nanostructures is developed. We employ inhomogeneous dynamical mean-field theory and the Kubo formula to derive relevant thermal transport coefficients, which take the form of matrices with respect to the planar indices. We show how to define the local versions of the current a...

A number of recent experiments report the low-temperature thermopower $\alpha$ and specific heat coefficients $\gamma=C_V/T$ of strongly correlated electron systems. Describing the charge and heat transport in a thermoelectric by transport equations, and assuming that the charge current and the heat current densities are proportional to the number...

We generalize the many-body formalism for the Peltier effect to the nonlinear/nonequilibrium regime cor- responding to large amplitude (spatially uniform but time-dependent) electric fields. We find a relationship between the expectation values for the charge current and for the part of the heat current that reduces to the Jonson-Mahan theorem in t...

The evolution of the thermopower EuCu{2}(Ge{1-x}Si{x}){2} intermetallics, which is induced by the Si-Ge substitution, is explained by the Kondo scattering of conduction electrons on the Eu ions which fluctuate between the magnetic 2+ and non-magnetic 3+ Hund's rule configurations. The Si-Ge substitution is equivalent to chemical pressure which modi...

Recent achievements in condensed matter physics and chemistry have brought us to a point where the properties of materials can be tuned at the quantum mechanical level. This book contains summaries of the Workshop on Correlated Thermoelectric Materials and the Conference on Concepts in Electron Correlation held in Hvar, Croatia, in 2005. The thermo...

The pressure-induced changes in the temperature-dependent thermopower S(T) and electrical resistivity ρ(T) of CeRu2Ge2 are described within the single-site Anderson model. The Ce ions are treated as impurities and the coherent scattering on different Ce sites is neglected. Changing the hybridization Γ between the 4f states and the conduction band a...

The nonlinear response of a material to a large electric field (steady or pulsed) often determines the ultimate performance of the material for electronics applications. The formalism for understanding nonlinear effects in conventional semiconductors is well understood. The formalism is less well developed for so-called "smart" materials that are t...

The thermoelectric properties of intermetallic compounds with Ce or Yb ions are explained by the single-impurity Anderson model which takes into account the crystal-field splitting of the 4{\it f} ground-state multiplet, and assumes a strong Coulomb repulsion which restricts the number of {\it f} electrons or {\it f} holes to $n_f\leq 1$ for Ce and...

A dynamical mean-field theory formalism is developed to exactly solve the non-equilibrium properties of the conduction electrons in the Falicov-Kimball model. We study the response of the conduction electrons on a hypercubic lattice in the half-filled case when an external spatially uniform time-dependent electric field is applied. The single-parti...

We calculate the f-electron spectral function using a Keldysh formalism for the Falicov-Kimball model in infinite dimensions. We study the region close to the quantum critical point on both the hypercubic and Bethe lattices. Comment: (2 pages, 3 figures, submitted to SCES'04)

The f-electron spectral function of the Falicov-Kimball model is calculated via a Keldysh-based many-body formalism originally developed by Brandt and Urbanek. We provide results for both the Bethe lattice and the hypercubic lattice at half filling. Since the numerical computations are quite sensitive to the discretization along the Kadanoff-Baym c...

Nonequilibrium quantum mechanics can be solved with the Keldysh formalism, which evolves the quantum mechanical states forward in time in the presence of a time-dependent field, and then evolves them backward in time, undoing the effect of the time-dependent field. The Feynman path integral over the Keldysh contour is employed to calculate the stro...

We analyze the thermal transport properties of the Falicov-Kimball model concentrating on locating regions of parameter space where the thermoelectric figure of merit ZT is large. We focus on high temperature for power generation applications and low temperature for cooling applications. We constrain the static particles (ions) to have a fixed conc...

The Falicov-Kimball model was introduced in 1969 as a statistical model for metal-insulator transitions; it includes itinerant and localized electrons that mutually interact with a local Coulomb interaction and is the simplest model of electron correlations. It can be solved exactly with dynamical mean-field theory in the limit of large spatial dim...

We present theoretical models which can account for the thermoelectric power (TEP) of metallic Kondo systems and in particular the compounds with Cerium or Ytterbium. At temperatures much above the Kondo temperature T_k, which is very small typically of order of some K, Kondo Ce or Yb compounds are well described by the Coqblin-Schrieffer...

We develop a formalism to solve the multicomponent Falicov–Kimball model with dynamical mean-field theory, allowing for all possible crystal-field couplings (including spin-orbit coupling). We apply these techniques to solve models of the intermediate-valence transition [as seen in YbInCu4 and EuNi2(Si1–xGex)2] in the simple limit of no crystal fie...

Dynamical mean field theory is used to solve the Falicov--Kimball model in the case where the f-ions have an internal structure. The solution provides a qualitative description of the properties of Eu-based intermetallic compounds which show anomalies due to a valence-change transition.

We study the low-temperature properties of a Kondo lattice using the large-N formalism. For a singular density of conduction states (DOS), we generalize the single-impurity result of Withoff and Fradkin: the strong-coupling fixed point becomes irrelevant if the DOS vanishes at the Fermi level E_F. However, for E_F close enough to the singularity, a...

The NATO sponsored Advanced Research Workshop on "Concepts in Electron Correlation" took place on the Croatian island of Hvar during the period from the 29th of September to the 3rd of October, 2002. The topic of electron correlation is a fundamental one in the field of condensed matter, and one that is being very actively studied both experimental...

Two errors were discovered in our manuscript. Our chemical potential was shifted by 0.02t* for the half-filled case, resulting in a nonzero thermopower, when it must vanish by symmetry. Also, our formula for the electronic thermal conductivity was missing a factor of T2 in the denominator.

The temperature dependence of the thermoelectric power (TEP) of Kondo Ce and Yb compounds is theoretically studied by a new approach: for T⪢TK, we start from the Coqblin–Schrieffer Hamiltonian including the crystalline field effect and we use a renormalized perturbation expansion with the coupling constants calculated by the “poor man's scaling” me...

Temperature dependence S(T) of the thermoelectric power of metallic systems with cerium and ytterbium ions exhibits some characteristic features, which can be used to classify these systems into distinct categories. The experimental data are explained by the Kondo scattering in the presence of the crystal field splitting and various shapes of S(T)...

The exact solution of the multi-component Falicov-Kimball model in infinite-dimensions is presented and used to discuss a new fixed point of valence fluctuating intermetallics with Yb and Eu ions. In these compounds, temperature, external magnetic field, pressure, or chemical pressure induce a transition between a metallic state with the f-ions in...

The magnetic susceptibility and susceptibility anisotropy of the quasibinary alloy system CexLa1-xCu2.05Si2 have been studied for low concentration of Ce ions. The single-ion description is found to be valid for x ≤0.09. The experimental results are discussed in terms of the degenerate Coqblin-Schrieffer model with a crystalline electric field spli...

The exact solution for the thermodynamic and dynamic properties of the infinite-dimensional multicomponent Falicov-Kimball model for arbitrary concentrations of d and f electrons is presented. The emphasis is on a descriptive derivation of important physical quantities by the equation-of-motion technique. We provide a thorough discussion of the f-e...

We prove the Jonson-Mahan theorem for the thermopower of the Falicov-Kimball model by solving explicitly for the correlation functions in the large dimensional limit. We prove a similar result for the thermal conductivity. We separate the results for thermal transport into the pieces of the heat current that arise from the kinetic energy and those...

The exact solution for the thermodynamic and dynamic properties of the infinite-dimensional multi-component Falicov-Kimball model for arbitrary concentration of d- and f-electrons is presented. The emphasis is on a descriptive derivation of important physical quantities by the equation of motion technique. We provide a thorough discussion of the f-...

The resistivity of a dilute alloy due to localized spin fluctuations (LSF) occurring on the impurity orbitals is given by a universal function of the temperature. The resistivity is finite at T=0, then decreases with temperature as T2, T, lnT and T-1 successively. The T2 and T behaviour are in good agreement with the experimental data on AIMn. The...

The resistance anomaly discovered by Coles in RhFe and occurring in several similar dilute alloys is shown to be of the same nature as the Kondo anomaly. The resistivity is due to localized spin fluctuations (LSF) and is given by a universal function of the temperature, increasing as T2, T and in T to tend finally to the unitarity limit. The charac...

The temperature dependence of the thermoelectric power (TEP) of Ce based intermetallic compounds exhibits some characteristic features, which allow these systems to be classified into several distinct categories. Our contribution explains the observed properties in a simple way. The high-temperature transport and thermodynamic properties of Ce comp...

Many experimental systems exist that possess charge-density-wave order in their ground state. While this order should be able to be described with models similar to those used for superconductivity, nearly all systems have a ratio of the charge-density-wave order parameter to the transition temperature that is too high for conventional theories. Re...

The spatial variation of the extra- and intraorbital electronic screening charge around the ion cores of chemisorbed atoms has been calculated within the non-orthogonal Anderson model. The overlap approximation for the hopping matrix elements has been used to treat the absorption of hydrogen on to a free-electron metal analytically and it was found...

The magnetoresistance of nearly magnetic transition metal-based alloys and actinides described by the one-band Wolff model is calculated within the localised spin fluctuation approximation. In the low-field, low-temperature limit the magnetoresistance is positive and proportional to H2/TK2(T<<H<<TK) with the coefficient of the H2 term being a parab...