Metal Insulator Transition
Mostrando 1-12 de 24 artigos, teses e dissertações.
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1. Microstructure and metal-insulator transition in single crystalline KMo4O6
High quality KMo4O6 single crystals with tetragonal structure (space group P4/mbm) have been prepared by fused salt electrolysis. The crystals were studied by scanning electron microscopy (SEM), X-ray diffractometry, electrical resistivity, and magnetization measurements. X-ray powder diffraction patterns and SEM have given some information on the growth of
Mat. Res.. Publicado em: 11/10/2012
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2. 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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3. Phenomenological Model for the metal-insulator transition in two dimensions
The resistivity measured in two-dimensional MOSFET geometry is modeled by considering that the resistivity is a function of the temperature and the areal density of charges (electrons or holes). The logistics differential equation is proposed for the behaviour of the resistivity as a function of temperature, so that the two phases are obtained in a natural m
Brazilian Journal of Physics. Publicado em: 2009-12
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4. 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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5. 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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6. 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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7. Localização de Anderson e transição metal-isolante em filmes de Pb1-xEuxTe do tipo p / Anderson Localization and Metal-Insulator Transition in p - type Filmes of Pb1-xEuxTe
Neste trabalho, realizamos o estudo da transição metal-isolante e da localização de Anderson na liga de Pb1-xEuxTe do tipo p para x variando de 0 até 0.1. As propriedades de transporte nessa liga (mobilidade, concentração de portadores e resistividade elétrica) foram obtidas utilizando o método de caracterização elétrica por efeito Hall entre as
Publicado em: 2008
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8. 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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9. Deposição de nano-camadas de VO2 por Magnetron Sputtering / Deposition of VO2 Nanolayers by Magnetron Sputtering
O dióxido de Vanádio (VO2) apresenta uma transição metal isolante (MIT) próxima da temperatura ambiente com uma grande variação em suas propriedades elétricas e ópticas. Tanto as propriedades elétricas e ópticas quanto a própria temperatura de transição dependem das características morfológicas do material. Neste trabalho, nano-camadas de óx
Publicado em: 2007
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10. Magneto-transporte no limite quantico em grafite e bismuto / Magnet transport in the quantum limit in graphite and bismuth
Esta tese é o resultado da investigação das propriedades elétricas e magnéticas de dois semimetais: bismuto (Bi) policristalino romboédrico e grafite pirolítica altamente orientada (HOPG). Inicialmente nós discutimos o efeito Hall no limite quântico, que acontece em amostras de grafite HOPG com certo grau de desordem e onde a desordem é reduzida. E
Publicado em: 2007
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11. 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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12. PHYSICS OF STRONGLY CORRELATED AND DISORDERED SYSTEMS / FÍSICA DE SISTEMAS FORTEMENTE CORRELACIONADOS E DESORDENADOS
In this thesis we study the properties of strongly correlated and disordered materials, using model Hamiltonians to describe them. The thesis is divided in two parts. The first one studies the periodic Anderson model used to describe the properties of a Kondo insulator. In particular we take Ce3Bi4Pt3 as a paradigmatic compound, characterized by a small gap(
Publicado em: 2004