Papers by Mucio Continentino
World Scientific Lecture Notes in Physics, 2001
Annals of Physics, 2016
Superconductivity in strongly correlated systems is a remarkable phenomenon that attracts a huge ... more Superconductivity in strongly correlated systems is a remarkable phenomenon that attracts a huge interest. The study of this problem is relevant for materials as the high T c oxides, pnictides and heavy fermions. In this work we study a realistic model that includes the relevant physics of superconductivity in the presence of strong Coulomb correlations. We consider a two-band model, since most of these correlated systems have electrons from at least two different atomic orbitals coexisting at their Fermi surface. The Coulomb repulsion is taken into account through a local repulsive interaction. Pairing is considered among quasiparticles in neighbouring sites and we allow for different symmetries of the order parameter. In order to deal with the strong local correlations, we use the well known slave boson approach that has proved very successful for this problem. Here we are interested in obtaining the zero temperature properties of the model, specifically its phase diagram and the existence and nature of superconducting quantum critical points. We show that these can arise by increasing the mixing between the two bands. Since this can be controlled by external pressure or doping, our results have a direct relation with experiments. We show that the superconductor-to-normal transition can be either to a metal, a correlated metal or to an insulator. Also we compare the relative stability of s and d-wave paired states for different regions of parameter space and investigate the BCS-BEC crossover in the two-band lattice model as function of the strength of the pairing interaction.
Quantum Scaling in Many-Body Systems
Contemporary Physics, 2019
Chapter 9 in the context of meta-stability. Finally, Chapter 10 discusses physical observations a... more Chapter 9 in the context of meta-stability. Finally, Chapter 10 discusses physical observations and theoretical correlations for the response of warm dense matter at ultra-high shock pressures, for example ranging up to 20 TPa. The topics addressed in each main chapter follow the overall theme of the text and cover a broad enough scope to make the book of interest to a wide readership, including scientists active in both static and shock compression. The book contains figures of high quality that enrich discussions of physical observations, theoretical concepts, and experimental methods. Schematics of the testing apparatus appropriate to each regime is particularly useful, as is the summary of applications and limitations of the early and recently developed experimental methods. The bibliography is notably comprehensive, consisting of on the order of 500 full references, wherein the reader may obtain further details on specific past research results. The fourth chapter on the history of high-pressure research is perhaps the most interesting for the non-specialist, containing a balance of technical and biographical information. The background discussions on fundamental analysis of dynamic and shock compression and material response in Chapters 1 and 2 are brief but adequate. This aspect could be viewed as beneficial or detrimental depending on the scope of information sought by the reader. Brevity renders the book accessible to a wide audience, without requiring proficiency beyond undergraduate mathematics. More rigorous, but also more difficult, derivations of the governing equations for shocks and structured compression and release waves are of course available elsewhere [1,2], as aremore sophisticatedmodeling treatments of condensed matter, e.g., equations of state for solids and liquids and nonlinear elasticity for crystals, resolving mechanics and thermodynamics across lengthand time-scales [3,4]. These more advanced presentations, however, require substantially more proficiency of the reader in the advanced graduate-level subjects of tensor mathematics, continuum mechanics, and materials physics. The intended audience of this book is graduate students and researchers in applied physics and related areas. The monograph is self-contained. It functions admirably as a reference work on historical and modern experimental methods in dynamic compression of condensedmatter. A unique aspect of this book, relative to others cited above and most on topics in shock compression science, is its applicability to very high pressure regimes using modern experimental tools. Summaries of prior findings are given with complementary figures of results data, but no formal problem sets usually found in course textbooks are included. The book therefore seems better as a research reference than a textbook for course instruction. The book is published by the very reputable Cambridge University Press. The quality of the editing, printing, and binding are excellent. Most of the figures are of high resolution and clarity, even those older or imported from works first published elsewhere. Formatting of the text and comprehensive reference list is nicely done, with minimal typographical glitches. Fonts are clear, in appropriate sizes; subscripts and superscripts large enough to be legible throughout. The book includes a Table of
Quantum Scaling in Many-Body Systems
Physica B: Condensed Matter, 2005
Quantum Scaling in Many-Body Systems
Quantum Scaling in Many-Body Systems
A. C. P. Lima, R. C. Bento Ribeiro, J. H. Correa, Fernanda Deus, M. S. Figueira, and Mucio A. Con... more A. C. P. Lima, R. C. Bento Ribeiro, J. H. Correa, Fernanda Deus, M. S. Figueira, and Mucio A. Continentino1∗ 1 Centro Brasileiro de Pesquisas F́ısicas, Rua Dr. Xavier Sigaud, 150, Urca 22290-180, Rio de Janeiro, RJ, Brazil Universidad Tecnológica Del Perú, Nathalio Sanchez, 125, Lima, Perú Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia, Departamento de Matemática, F́ısica e Computação, Rodovia Presidente Dutra km 298, 27537-000, Resende, RJ, Brazil and Instituto de F́ısica, Universidade Federal Fluminense, Av. Litorânea s/N, CEP: 24210-340, Niterói, RJ, Brasil
Quantum Scaling in Many-Body Systems
Quantum Scaling in Many-Body Systems
Journal of Physics F: Metal Physics, 1978
ABSTRACT The resistivity of an amorphous ferromagnet is calculated in the multiple scattering app... more ABSTRACT The resistivity of an amorphous ferromagnet is calculated in the multiple scattering approximation. The scattering at each magnetic site has a static component represented by a real parameter V which characterises the amount of disorder in the system and a dynamic component whose dominant contribution is the inelastic scattering of conduction electrons by diffusive modes associated with the longitudinal component of the magnetisation. For sufficiently large values of V the resistivity has a minimum as observed.
ABSTRACT We present an investigation of the magnetic properties of the pyroborates Mn2B2O5 and Mn... more ABSTRACT We present an investigation of the magnetic properties of the pyroborates Mn2B2O5 and MnMgB2O5 using magnetization and electron-paramagnetic-resonance measurements. The pyroborates have in common with another well studied family of borates, the warwickites, substructures in the form of ribbons where the metals are located. The homometallic Mn2B2O5 system is shown to be a conventional three-dimensional antiferromagnet with Neel temperature T(N)approximate to24 K. Its magnetization isotherms present steps indicating spin-flop-like transitions involving distinct pairs of metal sites. The heterometallic compound MnMgB2O5 shows a susceptibility with a power-law temperature dependence chi(T)proportional toT(-alpha), down to T=1.8 K and a magnetization with a power-law field dependence M(H)proportional toH((1-alpha)) at low temperatures. This behavior is characteristic of a random singlet phase, in this case, in a system with spin S=5/2. We discuss our magnetic results on the pyroborates in connection with their structure and compare them with those obtained in the warwickites.
Physical review letters, Jan 23, 2018
We present a study of thermal conductivity, κ, in undoped and doped strontium titanate in a wide ... more We present a study of thermal conductivity, κ, in undoped and doped strontium titanate in a wide temperature range (2-400 K) and detecting different regimes of heat flow. In undoped SrTiO_{3}, κ evolves faster than cubic with temperature below its peak and in a narrow temperature window. Such behavior, previously observed in a handful of solids, has been attributed to a Poiseuille flow of phonons, expected to arise when momentum-conserving scattering events outweigh momentum-degrading ones. The effect disappears in the presence of dopants. In SrTi_{1-x}Nb_{x}O_{3}, a significant reduction in lattice thermal conductivity starts below the temperature at which the average inter-dopant distance and the thermal wavelength of acoustic phonons become comparable. In the high-temperature regime, thermal diffusivity becomes proportional to the inverse of temperature, with a prefactor set by sound velocity and Planckian time (τ_{p}=(ℏ/k_{B}T)).
Journal of Physics F: Metal Physics
ABSTRACT The authors show that longitudinal magnetic excitations are responsible for an additiona... more ABSTRACT The authors show that longitudinal magnetic excitations are responsible for an additional T3/2 temperature dependent term in the decrease of the magnetisation of amorphous ferromagnets at low temperatures. This provides a possible explanation for the discrepancy on the values for the spin wave stiffness as measured by magnetisation and neutron scattering experiments. The discrepancy is compared to the anomalous temperature dependence of the resistivity, another effect of these longitudinal magnetic excitations.
Journal of Physics C: Solid State Physics
Journal of Physics C: Solid State Physics
Decimation techniques have already been used successfully to describe the densities of states of ... more Decimation techniques have already been used successfully to describe the densities of states of several types of disordered linear chains. In this paper the decimation procedure is extended for the case of Husimi cacti. These lattices are widely used as approximations to the continuous-random-network model for an ideal amorphous tetrahedral bonded semiconductor. The densities of states for disordered Husimi cacti
Journal of Physics C: Solid State Physics
The dynamics of a random ferromagnet with infinite-range exchange interactions and Gaussian distr... more The dynamics of a random ferromagnet with infinite-range exchange interactions and Gaussian distribution is studied. The Green function for the propagation of magnetic excitations is obtained in an exponential form which permits the use of techniques associated with problems involving random matrices. The magnetic properties of this system are obtained and compared with the ordered case.
Le Journal de Physique Colloques, 1988
We study the one dimensional random field Ising model using a real space renormalization group ap... more We study the one dimensional random field Ising model using a real space renormalization group approach. We consider both the ferromagnet and the antiferromagnet and show that they respond differently to a random field perturbation. We obtain exponents associated with the uniform and the random field problems.
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Papers by Mucio Continentino