Ferroelectric enhancement of superconductivity in compressively strained SrTiO${}_3$ films

Abstract

SrTiO${}_3$ is an incipient ferroelectric on the verge of a polar instability, which is avoided at low temperatures by quantum fluctuations. Within this unusual quantum paraelectric phase, superconductivity persists despite extremely dilute carrier densities. Ferroelectric fluctuations have been suspected to play a role in the origin of superconductivity by contributing to electron pairing. To investigate this possibility, we used optical second harmonic generation to measure the doping and temperature dependence of the ferroelectric order parameter in compressively strained SrTiO${}_3$ thin films. At low temperatures, we uncover a spontaneous out-of-plane ferroelectric polarization with an onset that correlates perfectly with normal-state electrical resistivity anomalies. These anomalies have previously been associated with an enhancement of the superconducting critical temperature in doped SrTiO${}_3$ films, directly linking the ferroelectric and superconducting phases. We develop a long-range mean-field Ising model of the ferroelectric phase transition to interpret the data and extract the relevant energy scales in the system. Our results support a long-suspected connection between ferroelectricity and superconductivity in SrTiO${}_3$, but call into question the role played by ferroelectric fluctuations.

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• Spin-orbit-coupled ferroelectric superconductivity
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Cited by in corpus (25)

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• Possible signatures of mixed-parity superconductivity in doped polar SrTiO3 films
• Anisotropic superconductivity mediated by ferroelectric fluctuations in cubic systems with spin-orbit coupling
• Isotope tuning of the superconducting dome of strontium titanate
• A switchable two-dimensional electron gas based on ferroelectric Ca:SrTiO${}_3$
• Enhanced Critical Field of Superconductivity at an Oxide Interface
• Anomalous superconducting diode effect in a polar superconductor
• Superconductivity induced by fluctuations of momentum-based multipoles
• Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics
• 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
• Generalized Rashba Electron-Phonon Coupling and Superconductivity in Strontium Titanate
• Spin-orbit coupling controlling the superconducting dome of artificial superlattices of quantum wells
• Ferro-ionic States and Domains Morphology in Hf${}_x$Zr${}_{1-x}$O${}_2$ Nanoparticles
• Majorana-Weyl cones in ferroelectric superconductors
• Domes of $T_c$ in single-band and multiband superconductors with finite-range attractive interactions
• Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO${}_3$
• Superconductivity in tin telluride films grown by molecular beam epitaxy
• Universally enhanced superconductivity and coexisting ferroelectricity at oxide interfaces
• Classification of multiorbital superconducting state based on augmented multipoles
• Modeling polar order in compressively strained SrTiO${}_3$
• Landau-Ginzburg theory of charge density wave formation accompanying lattice and electronic long-range ordering
• Violation of Pauli Limit at KTaO3(110) Interfaces
• A large modulation of electron-phonon coupling and an emergent superconducting dome in doped strong ferroelectrics
• Effects of doping on polar order in SrTiO${}_3$ from first-principles modeling