arXiv subjects

V. Dobrosavljevic

Publications and source records attributed to V. Dobrosavljevic.

At least 55 records · Page 3Linked to original sources

arXiv2004

Self-generated electronic heterogeneity and quantum glassiness in the high temperature superconductors

We present a systematic study of the spin and charge dynamics of copper oxide superconductors as a function of carrier concentration $x$. Our results portray a coherent physical picture, which reveals a quantum critical point at optimum doping ($x=x_{opt}$), and the formation of an inhomogeneous glassy state at $x < x_{opt}$. This mechanism is argued to arise as an intrinsic property of doped Mott insulators, and therefore to be largely independent of material quality and level of disorder.

cond-mat.str-el↗

arXiv2004

Mechanism of hopping transport in disordered Mott insulators

By using a combination of detailed experimental studies and simple theoretical arguments, we identify a novel mechanism characterizing the hopping transport in the Mott insulating phase of Ca$_{2-x}$Sr$_x$RuO$_4$ near the metal-insulator transition. The hopping exponent $α$ shows a systematic evolution from a value of $α=1/2$ deeper in the insulator to the conventional Mott value $α=1/3$ closer to the transition. This behavior, which we argue to be a universal feature of disordered Mott systems close to the metal-insulator transition, is shown to reflect the gradual emergence of disorder-induced localized electronic states populating the Mott-Hubbard gap.

cond-mat.str-el↗

arXiv2004

Quantum fluctuations and glassy behavior of electrons near metal-insulator transitions

Glassy behavior is a generic feature of electrons close to disorder-driven metal-insulator transitions. Deep in the insulating phase, electrons are tightly bound to impurities, and thus classical models for electron glasses have long been used. As the metallic phase is approached, quantum fluctuations become more important, as they control the electronic mobility. In this paper we review recent work that used extended dynamical mean-field approaches to discuss the influence of such quantum fluctuations on the glassy behavior of electrons, and examine how the stability of the glassy phase is affected by the Anderson and the Mott mechanisms of localization.

cond-mat.str-el↗

arXiv2004

Temperature dependent transport of correlated disordered electrons: elastic vs. inelastic scattering

Temperature dependent transport of disordered electronic systems is examined in the presence of strong correlations. In contrast to what is assumed in Fermi liquid approaches, finite temperature behavior in this regime proves largely dominated by inelastic electron-electron scattering. This conclusion is valid in the strong coupling limit, where the disorder, the correlations and the Fermi energy are all comparable, as in many materials near the metal-insulator transition.

cond-mat.str-el↗

arXiv2003

Localization effects and inelastic scattering in disordered heavy electrons

We study ground state and finite temperature properties of disordered heavy fermion metals by using a generalization of dynamical mean field theory which incorporates Anderson localization effects. The emergence of a non-Fermi liquid metallic behavior even at moderate disorder is shown to be a universal phenomenon resulting from local density of states fluctuations. This behavior is found to have a character of an electronic Griffiths phase, and can be thought of as a precursor of Anderson localization in a strongly correlated host. The temperature dependence of the conducting properties of the system reveal a non-trivial interplay between disorder and inelastic processes, which is reminiscent of the Mooij correlations observed in many disordered metals.

cond-mat.str-el↗

arXiv2003

Disorder Screening in Strongly Correlated Systems

Electron-electron interactions generally reduce the low temperature resistivity due to the screening of the impurity potential by the electron gas. In the weak-coupling limit, the magnitude of this screening effect is determined by the thermodynamic compressibility which is proportional to the inverse screening length. We show that when strong correlations are present, although the compressibility is reduced, the screening effect is nevertheless strongly enhanced. This phenomenon is traced to the same non-perturbative Kondo-like processes that lead to strong mass enhancements, but which are absent in weak coupling approaches. We predict metallicity to be strongly stabilized in an intermediate regime where the interactions and the disorder are of comparable magnitude.

cond-mat.str-el↗

arXiv2003

Glassy Behavior of Electrons as a Precursor to the Localization Transition

A theoretical model is presented, describing the glassy freezing of electrons in the vicinity of disorder driven metal-insulator transitions. Our results indicate that the onset of glassy dynamics should emerge before the localization transition is reached, thus predicting the existence of an intermediate metallic glass phase between the normal metal and the insulator.

cond-mat.dis-nn↗

arXiv2003

Glassy behavior of electrons near metal-insulator transitions

The emergence of glassy behavior of electrons is investigated for systems close to the disorder and/or interaction-driven metal-insulator transitions. Our results indicate that Anderson localization effects strongly stabilize such glassy behavior, while Mott localization tends to suppress it. We predict the emergence of an intermediate metallic glassy phase separating the insulator from the normal metal. This effect is expected to be most pronounced for sufficiently disordered systems, in agreement with recent experimental observations.

cond-mat.dis-nn↗

arXiv2003

Typical medium theory of Anderson localization: A local order parameter approach to strong disorder effects

We present a self-consistent theory of Anderson localization that yields a simple algorithm to obtain \emph{typical local density of states} as an order parameter, thereby reproducing the essential features of a phase-diagram of localization-delocalization quantum phase transition in the standard lattice models of disordered electron problem. Due to the local character of our theory, it can easily be combined with dynamical mean-field approaches to strongly correlated electrons, thus opening an attractive avenue for a genuine {\em non-perturbative} treatment of the interplay of strong interactions and strong disorder.

cond-mat.dis-nn↗

arXiv2002

Mean-field glassy phase of the random field Ising model

The emergence of glassy behavior of the random field Ising model (RFIM) is investigated using an extended mean-field theory approach. Using this formulation, systematic corrections to the standard Bragg-Williams theory can be incorporated, leading to the appearance of a glassy phase, in agreement with the results of the self-consistent screening theory of Mezard and Young. Our approach makes it also possible to obtain information about the low temperature behavior of this glassy phase. We present results showing that within our mean-field framework, the hysteresis and avalanche behavior of the RFIM is characterized by power-law distributions, in close analogy with recent results obtained for mean-field spin glass models.

cond-mat.dis-nn↗

arXiv2002

Landau theory of the Fermi-liquid to electron glass transition

A lattice model of spinless interacting electrons is used to formulate the Landau theory of the Fermi liquid to electron glass quantum phase transition. We demonstrate that the presence of additional random site energies does not affect the character of the transition, once the replica symmetry breaking is considered self-consistently at the mean-field level. Inside the glass phase, the low temperature conductivity assumes a non-Fermi liquid ~ T^{3/2} form, in agreement with recent experiments.

cond-mat.str-el↗

arXiv2001

Localization-induced Griffiths phase of disordered Anderson lattices

We demonstrate that local density of states fluctuations in disordered Anderson lattice models universally lead to the emergence of non-Fermi liquid (NFL) behavior. The NFL regime appears at moderate disorder (W = W_c) and is characterized by power-law anomalies, e. g. C/T ~ 1/T^{(1-α)}, where the exponent αvaries continuously with disorder, as in other Griffiths phases. This Griffiths phase is not associated with the proximity to any magnetic ordering, but reflects the approach to a disorder-driven metal-insulator transition (MIT). Remarkably, the MIT takes place only at much larger disorder W_{MIT} ~ 12 W_c, resulting in an extraordinarily robust NFL metallic phase.

cond-mat.str-el↗

arXiv2000

Novel metallic behavior in two dimensions

Experiments on a sufficiently disordered two-dimensional (2D) electron system in silicon reveal a new and unexpected kind of metallic behavior, where the conductivity decreases as σ(n_s,T)=σ(n_s,T=0)+A(n_s)T^2 (n_s-carrier density) to a non-zero value as temperature T->0. In 2D, the existence of a metal with dσ/dT>0 is very surprising. In addition, a novel type of a metal-insulator transition obtains, which is unlike any known quantum phase transition in 2D.

cond-mat↗

arXiv2000

Griffiths phase of the Kondo insulator fixed point

Heavy fermion compounds have long been identified as systems which are extremely sensitive to the presence of impurities and other imperfections. In recent years, both experimental and theoretical work has demonstrated that such disorder can lead to unusual, non-Fermi liquid behavior for most physical quantities. In this paper, we show that this anomalous sensitivity to disorder, as well as the resulting Griffiths phase behavior, directly follow from the proximity of metallic heavy fermion systems to the Kondo insulator fixed point.

cond-mat.str-el↗

arXiv1999

Melting of the Electron Glass

A model of spinless interacting electrons in presence of randomness is examined using an extended dynamical mean-field formulation. When the interaction strength is large as compared to the Fermi energy, a low temperature glassy phase is identified, which in our formulation corresponds to a replica-symmetry breaking instability. The glassy phase is characterized by a pseudo-gap in the single particle density of states, reminiscent of the Coulomb gap of Efros and Shklovskii. Due to ergodicity breaking, the ``zero-field cooled'' compressibility of this electron glass vanishes at T=0, consistent with absence of screening. When the Fermi energy exceeds a critical value, the glassy phase is suppressed, and normal metallic behavior is recovered.

cond-mat.dis-nn↗

arXiv1999

Destruction of the Mott Insulating Ground State of Ca_2RuO_4 by a Structural Transition

We report a first-order phase transition at T_M=357 K in single crystal Ca_2RuO_4, an isomorph to the superconductor Sr_2RuO_4. The discontinuous decrease in electrical resistivity signals the near destruction of the Mott insulating phase and is triggered by a structural transition from the low temperature orthorhombic to a high temperature tetragonal phase. The magnetic susceptibility, which is temperature dependent but not Curie-like decreases abruptly at TM and becomes less temperature dependent. Unlike most insulator to metal transitions, the system is not magnetically ordered in either phase, though the Mott insulator phase is antiferromagnetic below T_N=110 K.

cond-mat.str-el↗

arXiv1998

The RKKY interactions and the Mott Transition

A two-site cluster generalization of the Hubbard model in large dimensions is examined in order to study the role of short-range spin correlations near the metal-insulator transition (MIT). The model is mapped to a two-impurity Kondo-Anderson model in a self-consistently determined bath, making it possible to directly address the competition between the Kondo effect and RKKY interactions in a lattice context. Our results indicate that the RKKY interactions lead to qualitative modifications of the MIT scenario even in the absence of long range antiferromagnetic ordering.

cond-mat.str-el↗

arXiv1998

Localization effects in disordered Kondo lattices

We investigate the role of localization effects in the Kondo disorder mechanism for non-Fermi liquid behavior in disordered Kondo lattices. We find that the distribution of Kondo temperatures is strongly affected by fluctuations of the conduction electron density of states, a feature neglected in the previous treatment. For moderate disorder, the self-consistent distribution of Kondo temperatures flows to a universal log-normal form, irrespective of the form of the bare disorder distribution. For sufficient disorder, the system enters a Griffiths phase with diverging thermodynamic responses.

cond-mat.str-el↗