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Doctoral Thesis
DOI
https://doi.org/10.11606/T.97.2021.tde-18012022-174700
Document
Author
Full name
Frederico Benedetto Santos
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Lorena, 2021
Supervisor
Committee
Machado, Antonio Jefferson da Silva (President)
Bortolozo, Ausdinir Danilo
Granato, Enzo
Sandim, Maria José Ramos
Title in Portuguese
Síntese de amostras policristalinas de HfV2Ga4 e caracterização experimental de suas propriedades supercondutoras não convencionais
Keywords in Portuguese
Multibanda
Supercondutividade
Supercondutividade não convencional
Abstract in Portuguese
Nesse trabalho será apresentado um critério de separação entre supercondutores convencionais e não convencionais, além disso serão expostas e discutidas as propriedades estruturais e supercondutoras do composto ternário HfV2Ga4. A estrutura do material foi determinada por medidas de difratometria de raios X e a composição da fase foi definida utilizando espectroscopia de energia disperssiva (EDS). As propriedades supercondutoras foram avaliadas por medidas de susceptibilidade magnética, resistividade elétrica, calor específico e rotação e relaxação de spin de muon (μSR). Além disso, cálculos de primeiros princípios foram realizados trazendo importantes informações sobre a estrutura eletrônica e de bandas desse material. Divergências em relação a teoria BCS foram observadas principalmente nos diagramas de campo crítico inferior e superior e na dependência do calor específico com a temperatura. Por fim, medidas de μSR possibilitaram descrever o gap supercondutor por uma função de onda do tipo (s+d), todos esses resultados possibilitam categorizar esse material como um supercondutor multibanda.
Title in English
Synthesis of HfV2Ga4 polycrystalline samples and experimental characterization of their unconventional superconducting propertie
Keywords in English
Multiband
Superconductivity
Unconventional superconductivity
Abstract in English
In this work a criterion to separate conventional and unconventional supercondutors will be presented, moreover the structural and superconducting properties of the ternary compound HfV2Ga4 will be shown and discussed. This material structure was determined by X ray diffractometry and its chemical composition by energy dispersive spectroscopy (EDS), the superconducting properties were defined by magnetic susceptibility, electrical resistivity, specific heat and muon spic rotation and relaxation. Furthermore, first principles calculation were performed bringing to discussion important data on HfV2Ga4 electronic and band structure. Disagreements regarding BCS theory were found mainly in the lower and uper critical field diagrams and specific heat measurements as function of temperature. Finally, μSR results shown that the superconducting gap can be described by a (s+d) wave function, this set of results allow us to categorize this material as a multiband superconductor.
 
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EMT21001_C.pdf (5.30 Mbytes)
Publishing Date
2022-01-18
 
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