Insulator To Metal Phase Transition
Mostrando 1-11 de 11 artigos, teses e dissertações.
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1. Investigation of structural, electronic and magnetica properties of Ca2-xLaxFelrO6, Sr2-xLaxFelrO6 e TbMnO3 oxides / Investigação as propriedades estruturais, eletronicas e magneticas dos oxidos Ca2-xLaxFelrO6, Sr2-xLaxFelrO6 e TbMnO3
For many decades the transition metal oxides are subject of great scientific interest because of the wide variety of interesting physical properties and their potential technological applications. More recently, for example, oxides of transition metals with multiferroic properties have been considered as potential magneto-electronic devices. Many transition
Publicado em: 2010
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2. Efeitos de desordem na transição metal-isolante de Mott / Efects of disorder on the Mott metal-insulator transition
We determine the phase diagram of the disordered Hubbard Model as a function of temperature and interaction strength by means of the Statistical Dynamical Mean Field Theory. The metallic and insulating spinodal lines are traced for weak and moderate disorder using Quantum Monte Carlo as the impurity solver. We find that disorder pushes the spinodal lines to
Publicado em: 2009
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3. Sistemas eletrônicos em duas dimensões : desordem e resposta dinâmica
In disordered systems the pinning strength on the carriers due to impurities or defects is one of the most important mechanisms that produce insulator behavior. A transition to a metal phase should occur if a driving field is applied to the system. In the last three decades, such transition in two-dimensional systems has attracted much attention in light of
Publicado em: 2009
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4. Studies of inhomogeneity effects on properties of superconducting materials / Estudo da influencia de inomogeneidades nas propriedades de materiais supercondutores
In this work we study the physical properties of bismuth samples. Crystalline bulk bismuth, in the rhombohedral phase, is not superconducting, but, in the cubic phase, for example (obtained under pressure), in films and in the amorphous phase, may present superconducting transition. We observed superconductivity in a bismuth virgin powder and in samples prep
Publicado em: 2008
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5. Is the chiral phase transition induced by a metal-insulator transition?
We investigate the QCD Dirac operator with gauge configurations given by a liquid of instantons in the region of temperatures about the chiral phase transition. Both the quenched and unquenched cases are examined in detail. We present evidence of a localization transition in the low lying modes of the Dirac operator around the same temperature as the chiral
Brazilian Journal of Physics. Publicado em: 2007-03
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6. Preparation and characterization of La,Pr)CaMnO manganites / Preparação e caracterização de manganitas (La,Pr)CaMnO
Amostras policristalinas de La(5/8-y)Pr(y)Ca(3/8)MnO(3); 0 y 0.625; foram produzidas pelo método da mistura estequiométrica de óxidos e tratadas termicamente ao ar a 1400 oC. As amostras foram caracterizadas através de medidas de difração de raios-X, resistividade elétrica rho(T), susceptibilidade magnética chi(T) e magnetorresistividade rho(T, H = 5
Publicado em: 2005
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7. Efeitos de temperatura e de interação finita em sistemas desordenados correlacionados
The main goal of this work is to study the role of disorder in strongly correlated systems, where the electron-electron interaction is comparable to or dominates over the electron kinetic energy. Keeping this in mind, we solve the Hubbard model and the Anderson lattice model in the presence of disorder. The main theory in which our work is based is the Dynam
Publicado em: 2003
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8. Estudo da MagnetoimpedÃncia em La0;7Ca0;3MnO3 e La0;6Y0;1Ca0;3MnO3
In the present work, we report high frequency lock-in detection tecniques. The techniques were used to investigate La0:7Ca0:3MnO3 and La0:6Y0:1Ca0:3MnO3 manganites. The measurements were carried out at temperatures ranging from 50 to 300 K, and for applied magnetic fields up to 6 T, using both dc and ac currents. The frequency f of the ac current was varried
Publicado em: 2003
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9. Estrutura eletronica de polimeros conjugados : a influencia da desordem
The present work is dedicated to the theoretical study of effects observed in organic conjugated polymers in which disorder plays an important role. The following problems have been chosen for study: (1) Chemical reaction of polyanilines in acidic solutions. It is well known that protonation doping leads to insulator-to-metal transition in some forms of poly
Publicado em: 1992
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10. Critical transport properties of random metals in large magnetic fields
The threshold behavior of the transport properties of a random metal in the critical region near a metal–insulator transition is strongly affected by the measuring electromagnetic fields. In spite of the randomness, the electrical conductivity exhibits striking phase-coherent effects due to broken symmetry, which greatly sharpen the transition compared wit
The National Academy of Sciences of the USA.
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11. Spectroscopic studies of the vibrational and electronic properties of solid hydrogen to 285 GPa
We report Raman scattering and visible to near-infrared absorption spectra of solid hydrogen under static pressure up to 285 GPa between 20 and 140 K. We obtain pressure dependences of vibron and phonon modes consistent with results previously determined to lower pressures. The results indicate the stability of the ordered molecular phase III to the hig
The National Academy of Sciences.