Universität zu Köln

Wang, Jialu, Yang, Liangwei, Rischau, Carl Willem, Xu, Zhuokai, Ren, Zhi, Lorenz, Thomas ORCID: 0000-0003-4832-5157, Hemberger, Joachim, Lin, Xiao ORCID: 0000-0002-1773-1761 and Behnia, Kamran (2019). Charge transport in a polar metal. npj Quantum Mater., 4. LONDON: NATURE PUBLISHING GROUP. ISSN 2397-4648

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Abstract

The fate of electric dipoles inside a Fermi sea is an old issue, yet poorly explored. Sr1-xCaxTiO3 hosts a robust but dilute ferroelectricity in a narrow (0.0018 < x < 0.02) window of substitution. This insulator becomes metallic by removal of a tiny fraction of its oxygen atoms. Here, we present a detailed study of low-temperature charge transport in Sr1-xCaxTiO3-delta, documenting the evolution of resistivity with increasing carrier concentration (n). Below a threshold carrier concentration, n* (x), the polar structural-phase transition has a clear signature in resistivity and Ca substitution significantly reduces the 2 K mobility at a given carrier density. For three different Ca concentrations, we find that the phase transition fades away when one mobile electron is introduced for about 7.9 +/- 0.6 dipoles. This threshold corresponds to the expected peak in anti-ferroelectric coupling mediated by a diplolar counterpart of Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Our results imply that the transition is driven by dipole-dipole interaction, even in presence of a dilute Fermi sea. Charge transport for n < n*(x) shows a non-monotonic temperature dependence, most probably caused by scattering off the transverse optical phonon mode. A quantitative explanation of charge transport in this polar metal remains a challenge to theory. For n >= n* (x), resistivity follows a T-square behavior together with slight upturns (in both Ca-free and Ca-substituted samples). The latter are reminiscent of Kondo effect and most probably due to oxygen vacancies.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Wang, Jialu UNSPECIFIED UNSPECIFIED UNSPECIFIED Yang, Liangwei UNSPECIFIED UNSPECIFIED UNSPECIFIED Rischau, Carl Willem UNSPECIFIED UNSPECIFIED UNSPECIFIED Xu, Zhuokai UNSPECIFIED UNSPECIFIED UNSPECIFIED Ren, Zhi UNSPECIFIED UNSPECIFIED UNSPECIFIED Lorenz, Thomas UNSPECIFIED orcid.org/0000-0003-4832-5157 UNSPECIFIED Hemberger, Joachim UNSPECIFIED UNSPECIFIED UNSPECIFIED Lin, Xiao UNSPECIFIED orcid.org/0000-0002-1773-1761 UNSPECIFIED Behnia, Kamran UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-124519
DOI:	10.1038/s41535-019-0200-1
Journal or Publication Title:	npj Quantum Mater.
Volume:	4
Date:	2019
Publisher:	NATURE PUBLISHING GROUP
Place of Publication:	LONDON
ISSN:	2397-4648
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics II
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language FERROELECTRIC PHASE-TRANSITION; RESISTIVITY; TRANSFORMATIONS; TEMPERATURE; PB1-XGEXTE; SCATTERING; FILMS Multiple languages Materials Science, Multidisciplinary; Quantum Science & Technology; Physics, Applied; Physics, Condensed Matter Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/12451