Navegação Ciências Exatas e da Terra por Assunto "Supercondutividade"
Resultados 1-18 de 18
-
Co-cubstitution effects on the Fe valence in the BaFe2As2 superconducting compound : a study of hard x-ray absorption spectroscopy
(2011) [Artigo de periódico]The Fe K x-ray absorption near edge structure of BaFe₂-xCoxAs₂ superconductors was investigated. No appreciable alteration in shape or energy position of this edge was observed with Co substitution. This result provides ... -
Doping dependence of the electronic structure and magnetic order in high-tc superconductors
(1994) [Artigo de periódico]The local densities of states of an extended Hubbard model describing the Cu02 planes of superconducting cuprates are calculated by means of an approximate treatment that divides the lattice into Cu02 clusters. The exact ... -
Field and oxygen dependence of the magnetic irreversibility line in yba(2)cu(3)o(7-g)
(1994) [Artigo de periódico]We report on de magnetic susceptibility measurements in polycrystalline YBa2Cu30 7- δ as a function of the oxygen content in the limit of small δ. We focus mainly on the detailed behavior of the zero-fie1dcooled- field-cooled ... -
Fluctuation conductivity and microscopic granularity in bi-based high-temperature superconductors
(1997) [Artigo de periódico]Systematic conductivity measurements near Tc in granular (Bi,Pb)-Sr-Ca-Cu-O superconductors are presented, and focus is given on the interplay between thermal fluctuations and disorder at micro- and mesoscopic levels. ... -
Glass behavior and the h-t phase diagram of the high-tc ceramic superconductors yba2cu3o7, euba2cu3o7 and gdba2cu3o7
(1989) [Artigo de periódico]We report systematic field-cooled (PC) and zero-field-cooled (ZPC) diamagnetic susceptibility measurements in polycrystalline samples of the high-Tc oxide superconductors RBa2Cu30 7, where R =Y, Eu, or Gd. We focus mainly ... -
Granular superconductivity ina Ca-doped YBa/sub 2/Cu/sub 3/O/sub 7-σ single crystal : role of divalent impurities and the effect of applied field on the grain coupling
(2007) [Artigo de periódico]We investigate the effect of the divalent Ca atoms at the trivalent Y site of YBa2Cu3O7−δ on the magnetoconductivity and magnetic irreversibility of single crystals and a polycrystalline sample. The magnetic irreversibility ... -
Interplay between charge density wave and superconductivity in multiband systems with interband Coulomb interaction
(2021) [Artigo de periódico]In this work we study the competition or coexistence between charge density wave (CDW) and superconductivity (SC) in a two-band model system in a square lattice. One of the bands has a net attractive interaction (Jd) that ... -
Nature of insulating state in the three-band hubbard model : a tight-binding approach
(1995) [Artigo de periódico]We study the three-band Hubbard model, commonly used to describe the copper-oxygen planes of high-Tc superconductors, from the point of view of electronic properties. Utilizing perturbation theory around the atomic limit ... -
Phase diagram of the heavy fermion system YbFe/sub 2/Ge/sub 2/ under pressure
(2006) [Artigo de periódico]The phase diagram of the heavy fermion compound YbFe2Ge2 under high pressures P ≤ 18.2 GPa was obtained by electrical resistivity measurements. Pressure drives the system from a paramagnetic Fermi liquid state to a ... -
Pressure-induced phase transitions and volume changes in Hf02 up to Gpa
(1993) [Artigo de periódico]The phase transformations and pressure-volume dependence of Hf02 have been investigated at room temperature by angle-dispersive powder x-ray diffraction under high pressure to 50 GPa in a diamond anvil cell. The phase ... -
Roteiro para a experiência de levitação de um imã repelido por um supercondutor no ensino de física
(2004) [Artigo de periódico]Propõe-se um roteiro para a demonstração do fenômeno da supercondutividade através da experiência de levitação de um ímã repelido por uma amostra de YBa2Cu3O7. A experiência é baseada na manifestação do efeito Meissner, ... -
Spin liquid versus long-range magnetic order in the frustrated body-centered-tetragonal lattice
(2016) [Artigo de periódico]We show how spin-liquid (SL) states can be stabilized in a realistic three-dimensional model as a result of frustration. SU(n)-symmetric generalization of the Heisenberg model for quantum spin S operators is used to ... -
Superconductivity in disordered locally noncentrosymmetric materials : an application to CeRh2As2
(2021) [Artigo de periódico]Layered three-dimensional centrosymmetric crystals can exhibit characteristics of noncentrosymmetric mate rials. This happens when each individual layer alone lacks inversion but, when combined, inversion symmetry is ... -
Thermo‑magnetic signature of a superconducting multi‑band square with rough surface
(2021) [Artigo de periódico]In the present work, we will study the efect that the surface roughness of the sample has on the magnetic and thermodynamic properties in a mesoscopic superconducting meso-square under an external magnetic feld in a zero-feld ... -
Tópicos de física contemporânea no ensino médio : um texto para professores sobre supercondutividade
(1998) [Artigo de periódico]Este artigo é dirigido a professores de Física do ensino médio com o objetivo de tratar um tópico de Física Contemporânea - supercondutividade - não só no contexto dos conteúdos trabalhados na escola média, mas também a ... -
Tunneling spectroscopy of few-monolayer NbSe2 in high magnetic fields : triplet superconductivity and Ising protection
(2022) [Artigo de periódico]In conventional Bardeen-Cooper-Schrieffer superconductors, Cooper pairs of electrons of opposite spin (i.e., singlet structure) form the ground state. Equal-spin triplet pairs (ESTPs), as in superfluid 3 He, are of great ... -
Two scenarios for superconductivity in CeRh2As2
(2021) [Artigo de periódico]CeRh2As2, a nonsymmorphic heavy fermion material, was recently reported to host a remarkable temperature versus z-axis magnetic-field phase diagram with two superconducting phases. In this material, the two inequivalent ... -
Unconventional singlet-triplet superconductivity
(2022) [Artigo de periódico]Have you been lying awake wondering what symmetries determine whether a superconductor is spin-singlet, triplet, or both? We show that if one supplies additional degrees of freedom to BCS theory, spin-singlet can coexist ...