Title: Search for Kitaev spin liquid materials

Speaker: Dr. Tusharkanti Dey, Augsburg University, Germany

Abstract: The Kitaev model with anisotropic interaction between nearest neighbors on a honeycomb lattice offers an exact solution with spin liquid ground state [1]. This motivated detail investigation of the honeycomb lattice iridates (Na2IrO3 and Li2IrO3) but a spin liquid state has not been found [2]. For describing real materials, the model was modified as Heisenberg-Kitaev (HK) model [3]. A generalized form of the HK model has been proposed for the triangular lattice with a rich phase diagram [4]. We have synthesized the only triangular lattice iridate Ba3IrTi2O9 [5] which catalyzed the study of HK model on triangular lattice. Our thermodynamic measurements suggest a spin liquid ground state of this material. Recently we have synthesized Ba3InIr2O9 [6] which has a new motif of frustration with a combination of triangular and buckled honeycomb geometry. In this material, Ir has a single crystallographic site with an average charge state +4.5. Two neighboring IrO6 octahedra share one face forming Ir2O9 bioctahedra or dimer. The ions within the dimer share 9 electrons resulting in S=1/2 moments per dimer. Our thermodynamic measurements, neutron diffraction, nuclear magnetic resonance, and muon spin relaxation studies establish a gapless quantum spin liquid behavior in Ba3InIr2O9. In this talk, the design and synthesis of these interesting new materials and their magnetic properties in the context of Kitaev model will be discussed.

References:

1. A. Kitaev, Ann. Phys. 321, 2 (2006)

2. Y. Singh et. al., Phys. Rev. Lett. 108, 127203 (2012)

3. J. Chaloupka et. al., Phys. Rev. Lett. 105, 027204 (2010)

4. M. Becker et. al., Phys. Rev. B 91, 15535 (2015)

5. T. Dey et. al., Phys. Rev. B 86, 140405 (2012)

6. T. Dey et. al., Phys. Rev. B (2017) (in press)