Anomalies of upper critical field in the spinel superconductor LiTi${}_2$O${}_{4-\delta }$

Abstract

High-field electrical transport and point-contact tunneling spectroscopy were used to investigate superconducting properties of the unique spinel oxide, LiTi${}_2$O${}_{4-\delta }$ films with various oxygen content. We find that the upper critical field $B_{c2}$ gradually increases as more oxygen impurities are brought into the samples by carefully tuning the deposition atmosphere. It is striking that although the superconducting transition temperature and energy gap are almost unchanged, an astonishing isotropic $B_{c2}$ up to $\sim$ 26 Tesla is observed in oxygen-rich sample, which is doubled compared to the anoxic sample and breaks the Pauli limit. Such anomalies of $B_{c2}$ were rarely reported in other three dimensional superconductors. Combined with all the anomalies, three dimensional spin-orbit interaction induced by tiny oxygen impurities is naturally proposed to account for the remarkable enhancement of $B_{c2}$ in oxygen-rich LiTi${}_2$O${}_{4-\delta }$ films. Such mechanism could be general and therefore provides ideas for optimizing practical superconductors with higher $B_{c2}$.

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Cited by in corpus (6)

• Evidence for unconventional superconductivity in a spinel oxide
• Emergent superconductivity in single crystalline ${\mathrm{MgTi}}_2{\mathrm{O}}_4$ films via structural engineering
• Ionic liquid gating induced two superconductor-insulator phase transitions in spinel oxide Li${}_{1\pm x}$Ti${}_2$O${}_{4-\delta }$
• Epitaxial stabilization of an orthorhombic Mg-Ti-O superconductor
• Evolution of orbital excitations from insulating to superconducting MgTi${}_2$O${}_4$ films
• Surface-phase superconductivity in Mg-deficient V-doped MgTi${}_2$O${}_4$ spinel