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  • Letter
  • Open Access

Frustration-driven correlated parent states in the spinel superconductor LiTi2O4

Yuita Fujisawa1,2,*, Anjana Krishnadas1, Chia-Hsiu Hsu2,3, Takahito Takeda4, Sheng Liu1, Markel Pardo-Almanza1, Yukiko Obata1, Dyon van Dinter1, Tomonori Nakamura1 et al.

Kohei Yamagami5, Guoqing Chang3, Masaki Kobayashi4,6, Chang-Yang Kuo7,8, and Yoshinori Okada1,9,†

  • *Contact author: yuita-fujisawa@hiroshima-u.ac.jp
  • †Contact author: yoshinori-okada@oist.jp
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Phys. Rev. Research 8, L012032 – Published 4 February, 2026

DOI: https://doi.org/10.1103/q3xq-6p5f

Abstract

Geometrically frustrated transition-metal oxides provide fertile ground for the emergence of novel quantum states. In the spinel superconductor LiTi2O4 (superconducting critical temperature Tc≈13K, formal 3d0.5 system), we uncover a prominent dispersion kink near the Fermi energy accompanied by negative thermal expansion below a characteristic temperature T*≈150K. We propose that charge frustration in the pyrochlore lattice leads to a degenerate electronic arrangement on Ti3+/Ti4+ sites, giving rise to strong intersite Coulomb interactions below T*. Within this framework, negative thermal expansion arises from the Coulomb repulsion of 3d1 electrons, while the prominent kink reflects reduced screening due to enhanced correlations. These findings open up promising avenues for exploring exotic correlated states in frustrated pyrochlore lattices, which are situated near the 3d1 Mott state.

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Phys. Rev. Research 8, L012032– Published 4 February, 2026
  • Received 16 February 2024
  • Revised 25 July 2024
  • Accepted 5 December 2025
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