Anomalous magnetoresistance in the spinel superconductor LiTi2O4

Abstract

Transition-metal oxides offer an opportunity to explore unconventional superconductors, where the superconductivity (SC) is often interrelated with novel phenomena such as spin/charge order, fluctuations, and Fermi surface instability (1-3). LiTi2O4 (LTO) is a unique compound in that it is the only known spinel oxide superconductor. In addition to electron-phonon coupling, electron-electron and spin fluctuation contributions have been suggested as playing important roles in the microscopic mechanism for its superconductivity (4-8). However, the lack of high quality single crystals has thus far prevented systematic investigation of their transport properties (9). Here, we report a careful study of transport and tunneling spectroscopy in epitaxial LTO thin films. In the superconducting state, the energy gap was found to decrease as a quadratic function of magnetic field. In the normal state, an unusual magnetoresistance (MR) was observed where it changes from anisotropic positive to isotropic negative as the temperature is increased. A constant charge carrier concentration without any abrupt change in lattice parameters as a function of temperature suggests that the isotropic MR stems from the suppression of spin scattering/fluctuations, while the anisotropic term originates from an orbital contribution. These observations point to an important role strong correlations play in this unique superconductor.

4 figures, SI not included

References in corpus (8)

• Fermi-liquid instabilities at magnetic quantum phase transitions
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• Orbital-driven nematicity in FeSe
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• Emergence of Antiferromagnetic Correlation in LiTi2-xVxO4 via 7Li NMR

Cited by in corpus (8)

• Enhanced Superconductivity in TiO Epitaxial Thin Films
• Evidence for unconventional superconductivity in a spinel oxide
• Ionic liquid gating induced two superconductor-insulator phase transitions in spinel oxide Li${}_{1\pm x}$Ti${}_2$O${}_{4-\delta }$
• Raman study of electron-phonon coupling in thin films of LiTi${}_2$O${}_4$ spinel oxide superconductor
• Possible routes to superconductivity in the surface layers of V-doped Mg${}_{1-\delta }$Ti${}_2$O${}_4$ through multiple charge transfers and suppression of Jahn-Teller activity
• Epitaxial stabilization of an orthorhombic Mg-Ti-O superconductor
• Surface-phase superconductivity in Mg-deficient V-doped MgTi${}_2$O${}_4$ spinel
• Exploring the Electronic Nature of Spinel Oxides: A Review of Their Electron Interactions and Prospects