Superconductivity in 2D electron gas induced by high energy optical phonon mode and large polarization of the STO substrate

Abstract

Theory of superconductivity generated in one atomic layer thick two dimensional electron gas by a single flat band of high energy longitudinal optical phonons is considered. The polar dielectric $SrTi{O}_3$ (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell $FeSe$ layer is grown on its $\left(100\right)$ surface and on the interface with another dielectric like $LaAl{O}_3$ (LAO). We obtain a quantitative description of both systems solving the gap equation for $T_c$ without making use of approximations like the Kirzhnits Ansatz for arbitrary chemical potential $\mu$, electron-phonon coupling $\lambda$ and the phonon frequency $\Omega$, and direct (RPA) electron-electron repulsion strength $\alpha$. The high temperature superconductivity in 1UC$FeSe$/STO is possible due to a combination of three factors: high LO phonon frequency, large electron-phonon coupling $\lambda \sim 0.5$ and huge dielectric constant of the substrate suppression the Coulomb repulsion. It is shown that very low density electron gas in the interfaces is still capable of generating superconductivity of the order of $0.1$ K in LAO/STO. Superconductivity persists even on the band edge $\mu =0$.

19 pages, 7 figures

References in corpus (8)

• Electric Field Control of the LaAlO${}_3$/SrTiO${}_3$ Interface Ground State
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Electron-phonon interaction and charge carrier mass enhancement in SrTiO3
• High temperature superconducting FeSe films on SrTiO3 substrates
• Origin of the large phonon band-gap in SrTiO3 and the vibrational signatures of ferroelectricity in ATiO3 perovskite: First principles lattice dynamics and inelastic neutron scattering of PbTiO3, BaTiO3 and SrTiO3
• Superconductivity vs bound state formation in a two-band superconductor with small Fermi energy -- applications to Fe-pnictides/chalcogenides and doped SrTiO3
• Aspects of electron-phonon interactions with strong forward scattering in FeSe Thin Films on SrTiO${}_3$ substrates
• Microscopic mechanisms for the Fermi-liquid behavior of Nb-doped strontium titanate

Cited by in corpus (9)

• Interface high-temperature superconductivity
• Enhanced Superconducting Transition Temperature due to Tetragonal Domains in Two-Dimensionally Doped SrTiO${}_3$
• Decoupling carrier concentration and electron-phonon coupling in oxide heterostructures observed with resonant inelastic x-ray scattering
• Intrinsic interfacial van der Waals monolayers and their effect on the high-temperature superconductor FeSe/SrTiO${}_3$
• Phonon linewidth due to electron-phonon interactions with strong forward scattering in FeSe thin films on oxide substrates
• Soft phonons in the interface layer of the STO substrate can explain high temperature superconductivity in one unit cell FeSe
• Superconductivity in SrTiO${}_3$: dielectric function method for non-parabolic bands
• The phonon mechanism explanation of the superconductivity dichotomy between FeSe and FeS monolayers on STO and other substrates
• Plasmonic Cooper pairing in single layer graphene