Interplay between antiferrodistortive, ferroelectric and superconducting instabilities in Sr_{1-x}Ca_{x}$TiO_{3-δ}

Abstract

SrTiO${}_3$ undergoes a cubic-to-tetragonal phase transition at 105K. 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 non-isovalent 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 an open question, which gathers momentum in the context of the growing popularity of the paradigm linking unconventional superconductors and quantum critical points. We present a set of specific-heat, neutron-scattering and dielectric permittivity and polarization measurements on Sr${}_{1-x}$Ca${}_x$TiO${}_3$ ($0<x<0.009$) and a low-temperature electric conductivity in Sr${}_{0.9978}$Ca${}_{0.0022}$TiO${}_{3-\delta }$. Calcium substitution was found to enhance the transition temperature for both anti-ferrodistortive and ferroelectric transitions. Moreover, we find that Sr${}_{0.9978}$Ca${}_{0.0022}$TiO${}_{3-\delta }$ has a superconducting ground state. The critical temperature in this rare case of a superconductor with a ferroelectric parent, is slightly lower than in SrTiO${}_{3-\delta }$ of comparable carrier concentration. A three-dimensional phase diagram for Sr${}_{1-x}$Ca${}_x$TiO${}_{3-\delta }$ 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 neighbours.

arXiv comment9 pages, 9 figures

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Cited by in corpus (16)

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• Metallicity and superconductivity in doped strontium titanate
• Superconductivity at very low density: the case of strontium titanate
• Non-monotonic anisotropy in charge conduction induced by antiferrodistortive transition in metallic SrTiO${}_3$
• Phonon drag thermal Hall effect in metallic strontium titanate
• Superconductivity enhancement in polar metal regions of Sr${}_{0.95}$Ba${}_{0.05}$TiO${}_3$ and Sr${}_{0.985}$Ca${}_{0.015}$TiO${}_3$ revealed by the systematic Nb doping
• Different critical behaviors in cubic to trigonal and tetragonal perovskites
• Odd-parity superconductivity near inversion breaking quantum critical point in one dimension
• Ferroelectric order versus metallicity in Sr${}_{1-x}$Ca${}_x$TiO${}_{3-\delta }$ ($x=0.009$)
• Charge transport in oxygen-deficient EuTiO${}_3$: the emerging picture of dilute metallicity in quantum-paraelectric perovskite oxides
• Mechanism for Switchability in Electron-Doped Ferroelectric Interfaces
• Structure and dielectric properties of Ba${}_2$Cu${}_x$Y${}_{1-x}$TaO${}_{6-y}$ double perovskite
• Strain-engineered interaction of quantum polar and superconducting phases