The exactly solvable Kitaev model on a honeycomb lattice provides a novel platform to achieve an elusive quantum spin liquid and Majorana quasiparticles. In the quest for Kitaev honeycomb magnets, the two-dimensional layered ruthenate α-RuCl₃and iridates A₂IrO₃(A=Na, Li) are considered a prime candidate. In this seminar, I will discuss our group’s endeavor to search the predicted exotic states of matter in Kitaev candidate materials.

First, we present the combined thermodynamic, Raman and neutron scattering results ofα-RuCl₃. We provide experimental signatures of itinerant Majorana excitationsas a Y-shape dispersive excitation around the Γ-point and a magnetic continuum obeying Fermi statistics. The spin fractionalization is further corroborated by a two-stage release of magnetic entropy by (R/2)ln2. Second, we address an ensuing question whether Kitaev spin liquids are stabilized in the three-dimensional analogue of the honeycomb iridates, β-andγ-Li₂IrO₃. Using polarization-resolved Raman spectroscopy, we find that the temperature dependence of the Raman spectral weight is dominated by the thermal damping of fermionic excitations, similar to α-RuCl₃. Finally, we discuss an on-going project on the newly discovered copper iridate Cu₂IrO₃, being in closer proximity to the ideal geometry of the Kitaev honeycomb model than its predecessors A₂IrO₃(A = Na, Li) mainly due to the eclipsed stacking of adjacent layers. Preliminary characterizations reveal random Kitaev magentism, evading a long-range magnetic order, unlike A₂IrO₃.