Emergent spin-orbital states and magnetic regimes in the second-generation Kitaev magnets

Honeycomb iridate materials have been intensely studied in the past two decades due to the potential realization of a Kitaev spin-liquid phase. The basic ingredients of the Kitaev model including a honeycomb lattice, spin ½ ions, and bond-directional Ising-like interactions are present in materials such as α-Li₂IrO₃ and Na₂IrO₃. However, non-Kitaev interactions such as the Heisenberg and off-diagonal exchange are also present in real materials. These competing interactions create a complex phase diagram with non-collinear magnetic orders as well as the spin-liquid phase. In this talk, I will explain how topochemical methods can be used to tune the competing interactions and access different regimes in the phase diagram of Kitaev magnets. In a typical topochemical reaction, alkali ions are replaced by monovalent transition metal ions. As a result, the bond angles across the super-exchange paths change, providing a mechanism for tuning the relative strength of different exchange interactions and a potential route to discovering the quantum spin-liquid phase. I will present several materials synthesized via the topochemical reactions including Cu₂IrO₃ which exhibits a competition between static and dynamic magnetism [1,2,3], Ag₃LiIr₂O₆ which exhibits thermodynamic evidence of proximity to the Kitaev spin-liquid phase [4,5,6,7], and Ag₃LiRh₂O₆ that falls in a dramatically different region of the phase diagram away from the spin-liquid phase [8].

References:

[1] M. Abramchuk et al., J. Am. Chem. Soc. 139, 15371 (2017)

[2] E. Kenney et al., Phys. Rev. B 100, 094418 (2019)

[3] S. K. Takahashi et al., Phys. Rev. X 9, 031047 (2019)

[4] F. Bahrami et al. Phys. Rev. Lett 123, 237203 (2019)

[5] F. Bahrami et al. Phys. Rev. B 103, 094427 (2021)

[6] J. Wang et al. Phys. Rev. B 103, 214405 (2021)

[7] A. de la Torre, Phys. Rev. B 104, L100416 (2021)

[8] F. Bahrami, Science Advances, 8, eabl5671 (2022)