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Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2013
Author Dey Tusharkanti, Mahajan A. V., Kumar R., Koteswararao B., Chou F. C., Omrani A. A., Ronnow H. M.,
Project Mott Physics Beyond the Heisenberg Model in Iridates and Related Materials
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Original article (peer-reviewed)

Journal PHYSICAL REVIEW B
Volume (Issue) 88(13)
Page(s) 134425
Title of proceedings PHYSICAL REVIEW B
DOI 10.1103/PhysRevB.88.134425

Open Access

URL http://infoscience.epfl.ch/record/226815
Type of Open Access Repository (Green Open Access)

Abstract

We report the structural transformation of hexagonal Ba3YIr2O9 to a cubic double perovskite form (stable in ambient conditions) under an applied pressure of 8 GPa at 1273 K. While the ambient pressure synthesized sample undergoes long-range magnetic ordering at ∼4 K, the high-pressure (HP) synthesized sample does not order down to 2 K as evidenced from our susceptibility, heat capacity, and nuclear magnetic resonance (NMR) measurements. Further, for the HP sample, our heat capacity data have the form γT+βT3 in the temperature (T) range of 2–10 K with the Sommerfeld coefficient γ=10 mJ/mol-Ir K2. The 89Y NMR shift has no T dependence in the range of 4–120 K and its spin-lattice relaxation rate varies linearly with T in the range of 8–45 K (above which it is T independent). Resistance measurements of both the samples confirm that they are semiconducting. Our data provide evidence for the formation of a 5d-based, gapless, quantum spin-liquid in the cubic (HP) phase of Ba3YIr2O9. In this picture, the γT term in the heat capacity and the linear variation of 89Y 1/T1 arises from excitations out of a spinon Fermi surface. Our findings lend credence to the theoretical suggestion [Chen, Pereira, and Balents, Phys. Rev. B 82, 174440 (2010)] that strong spin-orbit coupling can enhance quantum fluctuations and lead to a QSL state in the double perovskite lattice.
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