Ferroelectric order versus metallicity in Sr1xCaxTiO3δ (x=0.009)

Johannes Engelmayer, Xiao Lin, Fulya Koç, Christoph P. Grams, Joachim Hemberger, Kamran Behnia, and Thomas Lorenz
Phys. Rev. B 100, 195121 – Published 13 November 2019

Abstract

We report on a thermal-expansion study of the ferroelectric phase transition in insulating Sr1xCaxTiO3 (x=0.009) and its evolution upon increasing charge-carrier concentration up to n60×1019cm3. Although electric polarization is screened by mobile charge carriers, we find clear signatures of the ferroelectric phase transition in the thermal-expansion coefficient α of the weakly doped metallic samples. Upon increasing n, the transition temperature TC(n) and the magnitude of the anomalies in α rapidly decrease up to a threshold carrier density n above which broadened anomalies remain present. There is no indication for a sign change of α as is expected for a pressure-dependent quantum phase transition with n as the control parameter. Thus, the ferroelectriclike transition is either continuously fading away or it transforms to another low-temperature phase above n, but this change hardly affects the temperature-dependent α(T) data.

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  • Received 23 July 2019
  • Revised 27 September 2019

DOI:https://doi.org/10.1103/PhysRevB.100.195121

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Johannes Engelmayer1, Xiao Lin1,*, Fulya Koç1, Christoph P. Grams1, Joachim Hemberger1, Kamran Behnia2,1, and Thomas Lorenz1,†

  • 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
  • 2Laboratoire de Physique et d'Étude des Matériaux (UMR 8213 CNRS-ESPCI), PSL Research University, 10 Rue Vauquelin, 75005 Paris, France

  • *Present address: School of Science, Westlake University, 18 Shilongshan Road, 310024, Hangzhou, China.
  • tl@ph2.uni-koeln.de

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Issue

Vol. 100, Iss. 19 — 15 November 2019

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