Abstract
AbstractThe fate of electric dipoles inside a Fermi sea is an old issue, yet poorly explored. Sr$${}_{1-x}$$1−xCa$${}_{x}$$xTiO$${}_{3}$$3 hosts a robust but dilute ferroelectricity in a narrow ($$0.0018\ <\ x\ <\ 0.02$$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 Sr$${}_{1-x}$$1−xCa$${}_{x}$$xTiO$${}_{3-\delta }$$3−δ, documenting the evolution of resistivity with increasing carrier concentration ($$n$$n). Below a threshold carrier concentration, $${n}^{* }(x)$$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 $$7.9\pm 0.6$$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 $$n\ <\ {n}^{* }(x)$$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 $$n\ge {n}^{* }(x)$$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.
Funder
National Natural Science Foundation of China
Publisher
Springer Science and Business Media LLC
Subject
Condensed Matter Physics,Electronic, Optical and Magnetic Materials
Cited by
26 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献