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Pedro Schlottmann

Bio: Pedro Schlottmann is an academic researcher from Florida State University. The author has contributed to research in topics: Kondo effect & Anderson impurity model. The author has an hindex of 42, co-authored 428 publications receiving 6593 citations. Previous affiliations of Pedro Schlottmann include Tufts University & ASTRON.


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Journal ArticleDOI
TL;DR: The specific heat, the susceptibility, the magnetic ordering, and the metal-to-semiconductor transition seen in the resistivity are consistent with the picture that Y{sup 3+} is replaced by Pr{sup 4+} with some degree of valence admixture of the Pr-Ba-Cu-O configuration.
Abstract: An extensive study of magnetic, thermal, transport, and structural properties of the alloy Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{ital y}} is presented. The endpoints of the alloy series are a high-temperature superconductor Y-Ba-Cu-O and an antiferromagnetic semiconductor (Pr-Ba-Cu-O, {ital T}{sub {ital N}}=17 K). The superconducting transition temperature is reduced with increasing Pr concentration following the Abrikosov-Gorkov pair-breaking curve with critical concentration {ital x}{sub cr}=0.62. Alloying also reduces the Neel temperature approximately linearly with the Y content, and there is a concentration region (0.4{lt}{ital x}{lt}0.6) where antiferromagnetism and superconductivity is suggested to coexist. The specific heat, the susceptibility, the magnetic ordering, and the metal-to-semiconductor transition seen in the resistivity are consistent with the picture that Y{sup 3+} is replaced by Pr{sup 4+} with some degree of valence admixture of the Pr{sup 3+} configuration.

274 citations

Journal ArticleDOI
TL;DR: A lattice model consisting of a single narrow band is introduced to describe some aspects of heavy electrons, including double occupancy of the sites and electrons on nearest-neighbor sites interact via a charge interaction and spin exchange.
Abstract: A lattice model consisting of a single narrow band is introduced to describe some aspects of heavy electrons. The model excludes double occupancy of the sites and electrons on nearest-neighbor sites interact via a charge interaction and spin exchange. The model is integrable in one dimension for some special values of the coupling constants. These cases are related to the SU(3) invariance. The Bethe-ansatz equations are obtained and ground-state and thermodynamic properties are discussed and solved in some limiting cases.

263 citations

Journal ArticleDOI
TL;DR: In this article, the degenerate Anderson model is used to obtain exact results for magnetic impurities in simple metals, in particular in the presence of mechanisms lifting the degeneracy of the f-level, e.g. crystalline fields, spin-orbit coupling and the magnetic field.

211 citations

Journal ArticleDOI
TL;DR: This Key Issues Review surveys some current experimental studies of iridates, a class of materials in which the lattice degrees of freedom play a critical role seldom seen in other materials, that presents some profound intellectual challenges that call for more investigations both experimentally and theoretically.
Abstract: Effects of spin-orbit interactions in condensed matter are an important and rapidly evolving topic. Strong competition between spin-orbit, on-site Coulomb and crystalline electric field interactions in iridates drives exotic quantum states that are unique to this group of materials. In particular, the 'J eff = ½' Mott state served as an early signal that the combined effect of strong spin-orbit and Coulomb interactions in iridates has unique, intriguing consequences. In this Key Issues Review, we survey some current experimental studies of iridates. In essence, these materials tend to defy conventional wisdom: absence of conventional correlations between magnetic and insulating states, avoidance of metallization at high pressures, 'S-shaped' I-V characteristic, emergence of an odd-parity hidden order, etc. It is particularly intriguing that there exist conspicuous discrepancies between current experimental results and theoretical proposals that address superconducting, topological and quantum spin liquid phases. This class of materials, in which the lattice degrees of freedom play a critical role seldom seen in other materials, evidently presents some profound intellectual challenges that call for more investigations both experimentally and theoretically. Physical properties unique to these materials may help unlock a world of possibilities for functional materials and devices. We emphasize that, given the rapidly developing nature of this field, this Key Issues Review is by no means an exhaustive report of the current state of experimental studies of iridates.

160 citations

Journal ArticleDOI
TL;DR: In this article, a spin-orbit interaction alters the balance between the competing energies so greatly that the spin degree of freedom alone is no longer a dominant force, and the underlying transport properties delicately hinge on the Ir-O-Ir bond angle via a strong magnetoelastic coupling.
Abstract: Sr${}_{2}$IrO${}_{4}$ exhibits an insulating state driven by spin-orbit interactions. We report two phenomena, namely, a large magnetoresistivity in Sr${}_{2}$IrO${}_{4}$ that is extremely sensitive to the orientation of magnetic field but exhibits no apparent correlation with the magnetization, and a robust metallic state that is induced by dilute electron (La${}^{3+}$) or hole (K${}^{+}$) doping for Sr${}^{2+}$ ions in Sr${}_{2}$IrO${}_{4}$. Our structural, transport, and magnetic data reveal that a strong spin-orbit interaction alters the balance between the competing energies so greatly that (1) the spin degree of freedom alone is no longer a dominant force, (2) the underlying transport properties delicately hinge on the Ir-O-Ir bond angle via a strong magnetoelastic coupling, and (3) a highly insulating state in Sr${}_{2}$IrO${}_{4}$ is proximate to a metallic state, and the transition is governed by lattice distortions that can be controlled via either the magnetic field or chemical doping.

148 citations


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TL;DR: In this article, a functional-integral approach to the dynamics of a two-state system coupled to a dissipative environment is presented, and an exact and general prescription for the reduction, under appropriate circumstances, of the problem of a system tunneling between two wells in the presence of dissipative environments to the spin-boson problem is given.
Abstract: This paper presents the results of a functional-integral approach to the dynamics of a two-state system coupled to a dissipative environment. It is primarily an extended account of results obtained over the last four years by the authors; while they try to provide some background for orientation, it is emphatically not intended as a comprehensive review of the literature on the subject. Its contents include (1) an exact and general prescription for the reduction, under appropriate circumstances, of the problem of a system tunneling between two wells in the presence of a dissipative environment to the "spin-boson" problem; (2) the derivation of an exact formula for the dynamics of the latter problem; (3) the demonstration that there exists a simple approximation to this exact formula which is controlled, in the sense that we can put explicit bounds on the errors incurred in it, and that for almost all regions of the parameter space these errors are either very small in the limit of interest to us (the "slow-tunneling" limit) or can themselves be evaluated with satisfactory accuracy; (4) use of these results to obtain quantitative expressions for the dynamics of the system as a function of the spectral density $J(\ensuremath{\omega})$ of its coupling to the environment. If $J(\ensuremath{\omega})$ behaves as ${\ensuremath{\omega}}^{s}$ for frequencies of the order of the tunneling frequency or smaller, the authors find for the "unbiased" case the following results: For $sl1$ the system is localized at zero temperature, and at finite $T$ relaxes incoherently at a rate proportional to $\mathrm{exp}\ensuremath{-}{(\frac{{T}_{0}}{T})}^{1\ensuremath{-}s}$. For $sg2$ it undergoes underdamped coherent oscillations for all relevant temperatures, while for $1lsl2$ there is a crossover from coherent oscillation to overdamped relaxation as $T$ increases. Exact expressions for the oscillation and/or relaxation rates are presented in all these cases. For the "ohmic" case, $s=1$, the qualitative nature of the behavior depends critically on the dimensionless coupling strength $\ensuremath{\alpha}$ as well as the temperature $T$: over most of the ($\ensuremath{\alpha}$,$T$) plane (including the whole region $\ensuremath{\alpha}g1$) the behavior is an incoherent relaxation at a rate proportional to ${T}^{2\ensuremath{\alpha}\ensuremath{-}1}$, but for low $T$ and $0l\ensuremath{\alpha}l\frac{1}{2}$ the authors predict a combination of damped coherent oscillation and incoherent background which appears to disagree with the results of all previous approximations. The case of finite bias is also discussed.

4,047 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize both the basic physics and unresolved aspects of BiFeO3 and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.
Abstract: BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

3,526 citations

Journal ArticleDOI
TL;DR: In this paper, a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions, including phase diagrams of manganite models, the stabilization of the charge/orbital/spin ordered half-doped correlated electronics (CE)-states, the importance of the naively small Heisenberg coupling among localized spins, the setup of accurate mean-field approximations, and the existence of a new temperature scale T∗ where clusters start forming above the Curie temperature, the presence of stripes in the system, and many others.

2,927 citations

01 Aug 1993
TL;DR: One-dimensional Bose-gas One-dimensional Heisenberg magnet Massive Thirring model Classical r-matrix Fundamentals of inverse scattering method Algebraic Bethe ansatz Quantum field theory integral models on a lattice Theory of scalar products Form factors Mean value of operator Q Assymptotics of correlation functions Temperature correlation functions Appendices References as discussed by the authors
Abstract: One-dimensional Bose-gas One-dimensional Heisenberg magnet Massive Thirring model Classical r-matrix Fundamentals of inverse scattering method Algebraic Bethe ansatz Quantum field theory integral models on a lattice Theory of scalar products Form factors Mean value of operator Q Assymptotics of correlation functions Temperature correlation functions Appendices References.

1,491 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the instabilities of the Fermi-liquid state of conduction electrons in metals with particular emphasis on magnetic quantum critical points, with the aim of assessing the validity of presently available theory.
Abstract: This review discusses instabilities of the Fermi-liquid state of conduction electrons in metals with particular emphasis on magnetic quantum critical points. Both the existing theoretical concepts and experimental data on selected materials are presented; with the aim of assessing the validity of presently available theory. After briefly recalling the fundamentals of Fermi-liquid theory, the local Fermi-liquid state in quantum impurity models and their lattice versions is described. Next, the scaling concepts applicable to quantum phase transitions are presented. The Hertz-Millis-Moriya theory of quantum phase transitions is described in detail. The breakdown of the latter is analyzed in several examples. In the final part experimental data on heavy-fermion materials and transition-metal alloys are reviewed and confronted with existing theory.

1,420 citations