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Phys. Rev. Lett. 101, 086404 (2008) [4 pages]

Band Jahn-Teller Instability and Formation of Valence Bond Solid in a Mixed-Valent Spinel Oxide LiRh2O4

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Yoshihiko Okamoto1,*, Seiji Niitaka1, Masaya Uchida1, Takeshi Waki2, Masashi Takigawa2, Yoshitaka Nakatsu3, Akira Sekiyama3, Shigemasa Suga3, Ryotaro Arita1,†, and Hidenori Takagi1,4
1RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako 351-0198, Japan
2Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa 277-8581, Japan
3Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
4Department of Advanced Materials, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa 277-8581, Japan

Received 16 June 2008; published 20 August 2008

We have synthesized a new spinel oxide LiRh2O4 with a mixed-valent configuration of Rh3+ and Rh4+. At room temperature, it is a paramagnetic metal, but on cooling, a metal-insulator transition occurs and a valence bond solid state is formed below 170 K. We argue that the formation of valence bond solid is promoted by a band Jahn-Teller transition at 230 K and the resultant confinement of t2g holes within the xy band. The band Jahn-Teller instability is also responsible for the observed enhanced thermoelectric power in the orbital-disordered phase above 230 K.

© 2008 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.101.086404
DOI:
10.1103/PhysRevLett.101.086404
PACS:
71.30.+h, 72.15.Jf

*Present address: Institute for Solid State Physics, Univ. of Tokyo, Kashiwanoha 5-1-5, Kashiwa 277-8581, Japan.

†Present address: Dept. of Applied Physics, Univ. of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.

 
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