Evidence for unconventional superconductivity in a spinel oxide

Abstract

The charge frustration with the mixed-valence state inherent to LiTi${}_2$O${}_4$, which is found to be a unique spinel oxide superconductor, is the impetus for paying special attention to reveal the existence of intriguing superconducting properties. Here, we report a pronounced fourfold rotational symmetry of the superconductivity in high-quality single-crystalline LiTi${}_2$O${}_4$ (001) thin films. Both the magnetoresistivity and upper critical field under an applied magnetic field manifest striking fourfold oscillations deep inside the superconducting state, whereas the anisotropy vanishes in the normal state, demonstrating that it is an intrinsic property of the superconducting phase. We attribute this behavior to the unconventional $d$-wave superconducting Cooper pairs with the irreducible representation of $E_g$ protected by $O_h$ point group in LiTi${}_2$O${}_4$. Our findings demonstrate the unconventional character of the pairing interaction in a three-dimensional spinel oxide superconductor and shed new light on the pairing mechanism of unconventional superconductivity.

arXiv comment8 pages, 4 figures

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Cited by in corpus (5)

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• 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
• Exploring the Electronic Nature of Spinel Oxides: A Review of Their Electron Interactions and Prospects
• Unique quantum metallic state in the titanium sesquioxide heterointerface superconductor