Re-entrant unconventional superconductivity induced by rare-earth substitution in Nd1-xEuxNiO2 thin films

Abstract

High temperature superconductivity is typically associated with strong coupling and a large superconducting gap, yet these characteristics have not been demonstrated in the nickelates. Here, we provide experimental evidence that Eu substitution in the spacer layer of Nd1-xEuxNiO2 (NENO) thin films enhances the superconducting gap, driving the system toward a strong-coupling regime. This is accompanied by a magnetic-exchange-driven magnetic-field-enhanced superconductivity. We investigate the upper critical magnetic field, Hc2, and superconducting gap of superconducting NENO thin films with x=0.2 to 0.35. Magnetoresistance measurements reveal magnetic-field-enhanced superconductivity in NENO films. We interpret this phenomenon as a result of interaction between magnetic Eu ions and superconducting states in the Ni dx2-y2 orbital. The upper critical magnetic field strongly violates the weak-coupling Pauli limit. Infrared spectroscopy confirms a large gap-to-Tc ratio $2\Delta k_B{T}_c\approx 5-6$, indicating a stronger coupling pairing mechanism in NENO relative to the Sr-doped NdNiO2. The substitution of Eu in the rare-earth layer provides a method to modify the superconducting gap in Nd-based nickelates, an essential factor in engineering high-Tc superconductivity in infinite-layer nickelates.

arXiv commentUnder Review & Revision

References in corpus (24)

• Maximally-localized generalized Wannier functions for composite energy bands
• Electronic structure of quantum materials studied by angle-resolved photoemission spectroscopy
• Phase diagram and superconducting dome of infinite-layer $\mathrm{N}{\mathrm{d}}_{1-\mathrm{x}}\mathrm{S}{\mathrm{r}}_{\mathrm{x}}\mathrm{Ni}{\mathrm{O}}_2$ thin films
• Infinite Layer LaNiO(2): Ni(1+)is not Cu(2+)
• A superconducting praseodymium nickelate with infinite layer structure
• Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering
• Nickelate superconductivity without rare-earth magnetism: (La,Sr)NiO${}_2$
• Phase competition in trisected superconducting dome
• Extreme magnetic field-boosted superconductivity
• Coupling strength of charge carriers to spin fluctuations in high-temperature superconductors
• Doping evolution of the Mott-Hubbard landscape in infinite-layer nickelates
• Rapid change of superconductivity and electron-phonon coupling through 19% doping in Bi2212
• Insulator-metal transition and topological superconductivity in UTe2 from a first-principles calculation
• Orbital Selective Superconductivity in a Two-band Model of Infinite-Layer Nickelates
• Isotropic Pauli-Limited Superconductivity in the Infinite Layer Nickelate Nd${}_{0.775}$Sr${}_{0.225}$NiO${}_2$
• Topological band and superconductivity in UTe${}_2$
• $f$-electron and magnetic ordering effects in nickelates LaNiO${}_2$ and NdNiO${}_2$: remarkable role of the cuprate-like $3d_{x^2-y^2}$ band
• Nickelate superconductors: an ongoing dialog between theory and experiments
• Low-energy electrodynamics of infinite-layer nickelates: evidence for d-wave superconductivity in the dirty limit
• ${}^{77}$Se NMR evidence for the Jaccarino-Peter mechanism in the field induced superconductor, $\lambda$(BETS)${}_2$FeCl${}_4$}
• A Nickelate Renaissance
• Novel dynamics and critical currents in fast superconducting vortices at high pulsed magnetic fields
• Distinct electridelike nature of infinite-layer nickelates and the resulting theoretical challenges to calculate their electronic structure
• BCS $d$-wave behavior in the THz electrodynamic response of electron-doped cuprate superconductors