Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics

Maria N. Gastiasoro; Maria Eleonora Temperini; Paolo Barone; Jose Lorenzana

doi:10.1103/PhysRevB.105.224503

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Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics

Maria N. Gastiasoro, Maria Eleonora Temperini, Paolo Barone, Jose Lorenzana

DOI 10.1103/PhysRevB.105.224503 · Physical Review B

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Abstract

Experimental evidence suggests that superconductivity in SrTiO3 is mediated by a soft transverse ferroelectric mode which, according to conventional theories, has negligible coupling with electrons. A phenomenological Rashba-type coupling has been proposed on symmetry arguments but a microscopic derivation is lacking. Here, we fill this gap and obtain a linear coupling directly from a minimal microscopic model of the electronic structure. We find that the effective electron-electron pairing interaction has a strong momentum dependence. This yields an unusual situation in which the leading s-wave channel is followed by a subleading p-wave state which shows a stronger pairing instability than the d-wave state. The bare Rashba coupling constant is estimated for the lowest band of doped SrTiO3 with the aid of first-principles computations. Extrapolating the estimation to the multiband regime we show that it can explain bulk superconductivity. For densities where the Meissner effect has not been observed an extra softening due to inhomogeneities is needed to explain the zero resistance state.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
SrTiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown