Calendar of Events

Speaker:  Alberto De La Torre

Abstract:  Honeycomb iridates with edge-sharing octahedra have been proposed to realize the Kitaev Quantum Spin Liquid (KQSL) model. In these compounds, it was predicted that the interplay of spin, lattice, and charge degrees of freedom give rise to a magnetic Hamiltonian with suppressed Heisenberg and dominant anisotropic ferromagnetic Ising-like nearest-neighbor interactions, a key ingredient of the KQSL [1]. However, both Na2 IrO3 and ?-Li2 IrO3 , the two most studied honeycomb iridates, display long-range magnetic order at low temperatures [2,3]. On the other hand, H3LiIr2O6 , recently synthesized via a topotactic reaction from ?-Li2 IrO3 , shows no evidence of ordering down to 50mK. While NMR and Knight shift measurements provide evidence of dynamically fluctuating spins at low temperatures, other thermodynamical probes reveal a departure from the pure Kitaev limit [4]. While H3LiIr2O6 is regarded as a Quantum Spin Liquid, it remains unclear how local disorder affects the magnetic interactions and what is the nature of the excitations in this compound [5].

Resonant inelastic X-ray scattering (RIXS) has emerged as the only technique able to resolve the magnetic excitations in honeycomb iridates proximal to the Kitaev limit. In this talk, I will show that the low-energy excitations in H3LiIr2O6 are characterized by an isotropic broad magnetic continuum that emerges from nearest-neighbor Kitaev interactions. We do not find evidence for short-range correlations or coherent modes. Our results confirm H3LiIr2O6 as a Quantum Spin Liquid with dominant Kitaev interactions and will constrain the theoretical model to identify the putative topological properties of this system.

[1] Chaloupka et al., Phys. Rev. Lett. 105, 027204 (2010) [2] Chun et al., Nat Phys 11, 462 (2015) [3] Chun et al., Phys. Rev. B 103, L020410 (2021) [4] Kitagawa et al., Nature 554, 341 (2018) [5] Knoelle et al., Phys. Rev. Lett. 122, 047202 (2019)

Host:  Sang-Wook Cheong