Interplay between antiferrodistortive, ferroelectric, and superconducting instabilities in Sr1-x Ca-x TiO3-delta

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de Lima, B. S. ; da Luz, M. S. ; Oliveira, F. S. ; Alves, L. M. S. ; dos Santos, C. A. M. ; Jomard, F. ; Sidis, Y. ; Bourges, P. ; Harms, S. ; Grams, C. P. ; Hemberger, J. ; Lin, X. ; Fauque, B. ; Behnia, K.

• Tipo de documento: Artigo Científico
• Fonte: PHYSICAL REVIEW B; v. 91, n. 4, p. 9-pg., 2015-01-08.

Resumo

SrTiO3 undergoes a cubic-to-tetragonal phase transition at 105 K. This antiferrodistortive transition is believed to be in competition with incipient ferroelectricity. Substituting strontium by isovalent calcium induces a ferroelectric order. Introducing mobile electrons to the system by chemical nonisovalent doping, on the other hand, leads to the emergence of a dilute metal with a superconducting ground state. The link between superconductivity and the other two instabilities is a question gathering momentum in the context of a popular paradigm linking unconventional superconductors and quantum critical points. We present a set of specific-heat, neutron-scattering, dielectric-permittivity, and polarization measurements on Sr1-x Ca-x TiO3 (0 < x < 0.009) and a study of low-temperature electric conductivity in Sr-0.9978 Ca-0.0022 TiO3-delta. Calcium substitution was found to enhance the transition temperature for both antiferrodistortive and ferroelectric transitions. Moreover, we find that Sr-0.9978 Ca-0.0022 TiO3-delta has a superconducting ground state. The critical temperature in this rare case of a superconductor with a ferroelectric parent is slightly lower than in SrTiO3-delta of comparable carrier concentration. A three-dimensional phase diagram for Sr1-x Ca-x TiO3-delta tracking the three transition temperatures as a function of x and delta results from this study, in which ferroelectric and superconducting ground states are not immediate neighbors. (AU)

• Processo FAPESP: 09/54001-2 - EMU: aquisição de equipamento cryo-free para caracterização de propriedades magnéticas por magnetometria de amostra vibrante (VSM)
• Beneficiário: Carlos Alberto Moreira dos Santos
• Modalidade de apoio: Auxílio à Pesquisa - Programa Equipamentos Multiusuários
• Processo FAPESP: 10/06637-2 - Estrutura cristalina e propriedades físicas do condutor anômalo KxMoO2-d
• Beneficiário: Leandro Marcos Salgado Alves
• Modalidade de apoio: Bolsas no Brasil - Doutorado