Osor Barišić

Institute of Physics

The generalized Drude formula is used to study conductivity properties of the two-dimensional weakly doped Holstein model with a free-electron-like dispersion. The relaxation processes associated with the scattering of conduction electrons by optical phonons are described in terms of a frequency- and temperature-dependent memory function. The imagi...

Measured transport properties of three representative cuprates are reproduced within the paradigm of two electron subsystems, itinerant and localized. The localized subsystem evolves continuously from the Cu 3d9\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \use...

Understanding the physical properties of unconventional superconductors as well as of other correlated materials presents a formidable challenge. Their unusual evolution with doping, frequency, and temperature has frequently led to non-Fermi-liquid (non-FL) interpretations. Optical conductivity is a major challenge in this context. Here, the optica...

Measured transport properties of three representative cuprates are reproduced within the paradigm of two electron subsystems, itinerant and localized. The localized subsystem evolves continuously from the Cu 3d$^9$ hole at half-filling and corresponds to the (pseudo)gapped parts of the Fermi surface. The itinerant subsystem is observed as a pure Fe...

A systematic analysis of phonon-plasmon coupled excitations in three-dimensional (3D) polar systems is provided through the prism of both raw and integrated electron energy loss spectroscopy (EELS) and phonon spectra in the whole relevant parametric space, spanned by the adiabaticity parameter and the electron-phonon interaction (EPI) strength. We...

Understanding the physical properties of unconventional superconductors as well as of other correlated materials presents a formidable challenge. Their unusual evolution with doping, frequency, and temperature, has frequently led to non-Fermi-liquid (non-FL) interpretations. Optical conductivity is a major challenge in this context. Here, the optic...

Using conformal field theory calculations of the energy spectrum, within the XXZ model we investigate effects of the flux insertion and the Umklapp term. We discuss two approaches to the evaluation of the Drude weight, the first corresponding to the linear response theory and the second corresponding to the twisted boson theory with the Umklapp ter...

Phonon-plasmon coupled excitations in heavily doped polar materials are addressed by examining bare and integrated electron energy loss spectroscopy (EELS) and phonon spectra. Results are obtained in the zero temperature limit for two semiconductors heavily discussed in the literature, namely GaAs and anatase TiO$_2$, characterized by the weak and...

Using conformal field theory calculations of the energy spectrum, within the XXZ model we investigate effects of the flux insertion and the Umklapp term. We discuss two approaches to the evaluation of the Drude weight, the first corresponding to the linear response theory and the second corresponding to the twisted boson theory with the Umklapp ter...

Foaming metals modulates their physical properties, enabling attractive applications where lightweight, low thermal conductivity or acoustic isolation are desirable. Adjusting the size of the bubbles in the foams is particularly relevant for targeted applications. Here we provide a method with a detailed theoretical understanding how to tune the si...

We examine the standard model of many-body localization (MBL), i.e., the disordered chain of interacting spinless fermions, by representing it as the network in the many-body (MB) basis of noninteracting localized Anderson states. By studying eigenstates of the full Hamiltonian, for strong disorders we find that the dynamics is confined up to very...

The scattering of electrons on impurities with internal degrees of freedom is bound to produce the signatures of the scatterer's own dynamics and results in nontrivial electronic transport properties. Previous studies of polaronic impurities in low-dimensional structures, like molecular junctions and one-dimensional nanowire models, have shown that...

We examine the standard model of many-body localization (MBL), i.e., the disordered chain of interacting spinless fermions, by representing it as the network in the many-body (MB) basis of noninteracting localized Anderson states. Studying eigenstates of the full Hamiltonian, we find for strong disorders that the dynamics is confined to disconnecte...

Numerous angle-resolved photoemission spectroscopy (ARPES) studies of a wide class of low-density metallic systems, ranging from doped transition metal oxides to quasi-two-dimensional interfaces between insulators, exhibit phonon sidebands below the quasiparticle peak as a unique hallmark of polaronic correlations. Here, we single out properties of...

We show that polaronic impurities, characterized by a significant electron-phonon interaction (EPI), may be a source of resonant electron scattering in bulk systems. Using Green's function formalism, partial cross-sections for elastic and inelastic processes are calculated exactly to all orders in the static and the dynamic interaction between the...

A theoretical study of the angle resolved photoemission spectra (ARPES) is presented for metallic systems with a low concentration of carriers interacting with phonons via the weak screened Fr\"ohlich interaction. We show that for an efficient analysis of the screening one has to render the experimental ARPES intensity into the imaginary part of th...

Thermal conductivity (κ) plays an essential role in functional devices. It is advantageous to design materials where one can tune κ in a wide range according to its function: single-crystals and nanowires of anatase polymorph of titanium dioxide, broadly used in applications ranging from photovoltaics, reflective coatings to memristors, have been s...

Within the standard model of many-body localization, i.e., the disordered chain of spinless fermions, we investigate how the interaction affects the many-body states in the basis of noninteracting localized Anderson states. From this starting point we follow the approach that uses a reduced basis of many-body states. Such approach proves to be effi...

We present a review of recent theoretical results concerning the many-body localization (MBL) phenomenon, with the emphasis on dynamical density correlations and transport quantities. They are shown to be closely related, providing a comprehensive description of the ergodic-to-nonergodic transition, consistent with experimental findings. While the...

We present a review of recent theoretical results concerning the many-body localization (MBL) phenomenon, with the emphasis on dynamical density correlations and transport quantities. They are shown to be closely related, providing a comprehensive description of the ergodic-to-nonergodic transition, consistent with experimental findings. While the...

We present numerical results within the one-dimensional disordered Hubbard model for several characteristic indicators of the many-body localization (MBL). Considering traditionally studied charge disorder (i.e., the same disorder strength for both spin orientations) we find that even at strong disorder all signatures consistently show that while c...

We present numerical results within the one-dimensional disordered Hubbard model for several characteristic indicators of the many-body localization (MBL). Considering traditionally studied charge disorder (i.e., the same disorder strength for both spin orientations) we find that even at strong disorder all signatures consistently show that while c...

We present a numerical study of the many-body localization (MBL) phenomenon within an anisotropic Heisenberg model with random local fields. Taking the dynamical spin conductivity $\sigma(\omega)$ as the test case, we show that finite-size statistical fluctuations of $\sigma(\omega)$ spectra scale differently for the anisotropy $\Delta=0$, correspo...

Nature Communications 7 Article number: 1038610.1038/ncomms10386 (2016); Published January272016; Updated February262016 In the original PDF version of this Article, which was published on 27 January 2016, the publication date was incorrectly given as 27 January 2015. This has now been corrected in the PDF; the HTML version of the paper was correc...

Supplementary Figures 1-2, Supplementary Notes 1-2 and Supplementary References.

Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 (LAO/STO) that hosts two-d...

A large Ud theory is constructed for the metallic state of high-Tc cuprates. The Emery three-band model, extended with Ox-Oy hopping tpp, and with , is mapped on slave fermions. The Dyson time-dependent diagrammatic theory in terms of the Cu-O hopping tpd, starting from the nondegenerate unperturbed ground state, is translationally and asymptotical...

We report resistivity, thermoelectric power and thermal conductivity of MoS2 single crystals prepared by chemical vapour transport (CVT) method using I2, Br2 and TeCl4 as transport agents. The material presents low-lying donor and acceptor levels, which dominate the in-plane charge transport. Intercalates into the Van der Waals gap strongly influen...

We report on the temperature dependence of thermal conductivity of single crystalline and polycrystalline organometallic perovskite CH3NH3PbI3. The comparable absolute values and temperature dependence of the two samples’ morphologies indicate the minor role of the grain boundaries on the heat transport. Theoretical modeling demonstrates the import...

A theory of the underlying metallic state of large-U$_d$ high-Tc cuprates is presented starting from the covalent Cu-2O 3-band model associated with a sufficiently small copper occupancy. U$_d=\infty$ is dealt by the slave fermion approach. Diagrammatic low order NCA theory in terms of the Cu-O hopping is supplemented with two independent slave par...

We report on the interplay of localized and extended degrees of freedom in the metallic state of high-temperature superconductors in a multiband setting. Various ways in which the bare magnetic response may become incommensurate are measured against both phenomenological and theoretical requirements. In particular, the pseudogap temperature is typi...

Oxygen vacancies created in anatase TiO2 by UV photons (80 - 130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission (ARPES) reveals that the quasiparticles are large polarons. These results indicate that anatase can be tuned from an insulator to a polaron gas t...

The titanium oxide TiO2 has been object of extensive studies because of its suitability in many practical fields, ranging from photovoltaic applications, to catalysis, memristors, and others. As for many other transition metal oxides, great attention has been devoted to the impact on the electronic structure of different doping mechanisms, either e...

A brief analysis of ARPES, Raman, and neutron data is used to show the importance of the oxygen degree of freedom for the metallic phase of cuprate high-Tc superconductors. It is based on published results and a number of new calculations, relevant to Raman and neutron scattering in the metallic underdoped and optimally doped regime. They are place...

Large U d theories of high-T c cuprates often start from the ionic limit in which one charge per CuO2 unit cell is localized on the copper site and involved in AF correlations with neighboring sites. AF correlations are promoted by a relatively small exchange J and the motion of holes by is described by the t–J models with narrow effective bands. H...

A large-Ud theory is constructed for the metallic state of high-Tc cuprates. The Emery three-band model, extended with Ox-Oy hopping tpp, and with Ud tending to infinity, is mapped on slave fermions. The Dyson time-dependent diagrammatic theory in terms of the Cu-O hopping tpd, which starts from the nondegenerate unperturbed ground state, is transl...

Dynamical conductivity in a disordered one-dimensional model of interacting fermions is studied numerically at high temperatures and in the weak-interaction regime in order to find a signature of many-body localization and vanishing d.c. transport coefficients. On the contrary, we find in the regime of moderately strong local disorder that the d.c....

The single bipolaron problem is examined in the context of the 1D Holstein-Hubbard model, emphasizing analogies and differences with respect to the complementary single polaron physics. The bipolaron band structure below the phonon threshold is revealed, showing a complex relationship between numerous excited bands as the adiabatic limit is approac...

The large U_d theory, based on the Emery three band model extended with the Ox-Oy hopping t_pp, is constructed for the metallic state of high-Tc cuprates, using the mapping on the slave fermion theory. The time-dependent diagrammatic theory in terms of the Cu-O hopping t_pd starts from the locally gauge invariant state with vanishing occupation of...

We explore the effect of a (non) magnetic impurity on the thermal transport of the spin-1/2 Heisenberg chain model. This unique system allows to probe Kondo-type phenomena in a prototype strongly correlated system. Using numerical diagonalization techniques we study the scaling of the frequency dependent thermal conductivity with system size and ho...

We have investigated anisotropic electrical resistivity and thermoelectric power of the ypsilon-phase Al-Ni-Co (Y-Al-Ni-Co) decagonal approximant with composition Al(76)Co(22)Ni(2). The crystalline-direction-dependent measurements were performed along three orthogonal directions a*, b and c of the Y-Al-Ni-Co unit cell, where (a, c) monoclinic atomi...

The Bechgaard salts and the high Tc cuprates are described by two and three band models, respectively, with the lowest band (nearly) half filled. In organics the interactions are small, while in cuprates the repulsion Ud on the Cu-site is the largest energy. The Mott-AF state is stable in undoped materials in both cases. In the metallic phase of cu...

The effect of a single static impurity on the many-body states and on the spin and thermal transport in the one-dimensional anisotropic Heisenberg chain at finite temperatures is studied. Whereas the pure Heisenberg model reveals Poisson level statistics and dissipationless transport due to integrability, we show using the numerical approach that a...

Atomic repulsion $U_d$ on the Cu site in high T$_c$ cuprates is large but, surprisingly, some important properties are consistent with moderate couplings. The time dependent perturbation theory with slave particles is therefore formulated in the $U_d\to\infty$ limit for the metallic phase in the physically relevant regime of the three-band Emery mo...

We have investigated anisotropic physical properties (magnetic susceptibility, electrical resistivity, thermoelectric power, Hall coefficient, and thermal conductivity) of Y-Al-Ni-Co decagonal approximant with composition Al76Co22Ni2. The crystalline-direction-dependent measurements were performed along three orthogonal directions a∗, b, and c of t...

We present numerical investigations of the short-time dynamics at criticality in the 1D Potts model with power-law decaying interactions of the form 1/r1+σ. The scaling properties of the magnetization, autocorrelation function and time correlations of the magnetization are studied. The dynamical critical exponents θ' and z are derived in the cases...

The behavior of the 1D Holstein polaron is described, with emphasis on lattice coarsening effects, by distinguishing between adiabatic and nonadiabatic contributions to the local correlations and dispersion properties. The original and unifying systematization of the crossovers between the different polaron behaviors, usually considered in the lite...

The behavior of the 1D Holstein polaron is described, with emphasis on lattice coarsening effects, by distinguishing between adiabatic and nonadiabatic contributions to the local correlations and dispersion properties. The original and unifying systematization of the crossovers between the different polaron behaviors, usually considered in the lite...

In the context of the Holstein polaron problem, it is shown that the dynamical mean-field theory (DMFT) corresponds to the summation of a special class of local diagrams in the skeleton expansion of the self-energy. In the real space representation, these local diagrams are characterized by the absence of vertex corrections involving phonons at dif...

A Comment on the Letter by Mona Berciu, Phys. Rev. Lett.PRLTAO0031-9007 97, 036402 (2006)10.1103/PhysRevLett.97.036402. The authors of the Letter offer a Reply.

A new numerical method is proposed for determining the low-frequency dynamics of the charge carrier coupled to the deformable quantum lattice. As an example, the polaron band structure is calculated for the one-dimensional Holstein model. The adiabatic limit on the lattice, which cannot be reached by other approaches, is investigated. In particular...

The translationally invariant diagrammatic quantum perturbation theory (TPT) is applied to the polaron problem on the 1D lattice, modeled through the Holstein Hamiltonian with the phonon frequency omega0, the electron hopping t and the electron-phonon coupling constant g. The self-energy diagrams of the fourth-order in g are calculated exactly for...

The polaron formation is investigated in the intermediate regime of the Holstein model by using an exact diagonalization technique for the one-dimensional infinite lattice. The numerical results for the electron and phonon propagators are compared to the nonadiabatic weak-and strong-coupling perturbation theories, as well as with the harmonic adiab...

The polaron formation is investigated in the intermediate regime of the Holstein model by using an exact diagonalization technique for the one-dimensional infinite lattice. The numerical results for the electron and phonon propagators are compared with the nonadiabatic weak- and strong-coupling perturbation theories, as well as with the harmonic ad...

The translationally invariant diagrammatic quantum perturbation theory (TPT) is applied to the polaron problem on the 1D lattice, modeled through the Holstein Hamiltonian with the phonon frequency ω0, the electron hopping t and the electron-phonon coupling constant g. The self-energy diagrams of the fourth-order in g are calculated exactly for an i...

An exact-diagonalization technique is used to investigate the low-lying excited polaron states in the Holstein model for the infinite one-dimensional lattice. For moderate values of the adiabatic ratio, a comprehensive picture, involving three excited (coherent) polaron bands below the phonon threshold, is obtained. The coherent contribution of the...

The paper deals with the ground and the first excited state of the polaron in the one-dimensional Holstein model. Various variational methods are used to investigate both the weak-coupling and strong-coupling case, as well as the crossover regime between them. Two of the methods, presented here, introduce interesting elements to the understanding o...

The effect of the quenched random dilution on the ferromagnetic transitions, in particular, the conversion from the first- to second-order transition is discussed. The new results are presented for the diluted three-dimensional three-state Potts model. The critical exponents of the disorder-induced second-order phase transition are derived by the f...

The structure of the translationally-invariant diagrammatic perturbation theory for one polaron is examined on the 1D discrete lattice described by the Holstein Hamiltonian. The latter is characterized by the electron hopping t, the phonon frequency w0 and the electron-phonon coupling g. It is shown that the polaron localization (and translation) p...