Origin of Optical Transparency in a Transparent Superconductor LiTi2O4

Takeo Ohsawa, Naoomi Yamada, Akichika Kumatani, Yoshitaka Takagi, Tohru Suzuki, Ryouta Shimizu, Susumu Shiraki, Tsutomu Nojima, Taro Hitosugi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


We discuss the transparent conducting mechanism of LiTi2O4. In the Bardeen-Cooper-Schrieffer (BCS) framework, achieving a high superconducting transition temperature (Tc) requires high carrier density at the Fermi energy. This requirement suppresses the emergence of transparent superconductivity at high temperature because the high carrier density results in optical absorption in the visible region. In this paper, we here demonstrate transparent superconducting properties with Tc exceeding 13 K for epitaxial thin films of the spinel LiTi2O4(111). Although LiTi2O4 has a very high carrier density in excess of 1022 cm-3, the film exhibits high transmittance in the visible region, which cannot be explained by the model for conventional transparent conductors. We show that a large effective mass plays a key role in the optical transparency in the visible region. These studies provide the material design principles for transparent conductors that would enable the development of highly efficient optoelectronic devices.

Original languageEnglish
Pages (from-to)517-522
Number of pages6
JournalACS Applied Electronic Materials
Issue number2
Publication statusPublished - 2020 Feb 25


  • LiTiO
  • band structures
  • superconductivity
  • thin films
  • transparency

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrochemistry
  • Materials Chemistry


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