Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Poster Session: Correlated Electrons 1

TT 19.51: Poster

Montag, 20. März 2017, 15:00–19:00, P2-EG

"Ferroelectric" phase transition in conducting Sr_1−xCa_xTiO_3−δ — •Dennis Finck, Steffen Harms, Xiao Lin, Christoph P. Grams, Johannes Engelmayer, Thomas Lorenz, and Joachim Hemberger — II. Physikalisches Institut, Universität zu Köln, Germany

Insulating SrTiO₃ is a so-called quantum paraelectric close to an ferroelectric instability. On the one hand, the substitution of strontium ions by smaller and isovalent calcium ions induces a ferroelectric phase at finite temperatures. On the other hand, SrTiO₃ becomes metallic and even superconducting at temperatures below 1K after charge carrier doping [1].

Therefore the question arises what happens when both effects are combined. Here, we provide experimental evidence for a polar ground state also in the metallic compound. As mobile charge carriers screen the electric polarization, it is technically not possible to directly measure ferroelectricity. Thus, our conclusion ist based on measurements of sound velocities and thermal expansions.

Funded through the Institutional Strategy of the University of Cologne within the German Excellence Initiative.

[1] B. S. de Lima, M. S. da Luz, F. S. Oliveira, L. M. S. Alves, C. A. M. dos Santos, F. Jomard, Y. Sidis, P. Bourges, S. Harms, C. P. Grams, J. Hemberger, X. Lin, B. Fauqué, and K. Behnia,
Phys. Rev. B 91, 045108 (2015)