Prof Radu Coldea

Abstract:

© 2019 American Physical Society. The excitations in honeycomb α-Li2IrO3 have been investigated with high-resolution resonant inelastic X-ray scattering (RIXS) at the O K edge. The low-energy response is dominated by a fully resolved ladder of excitations, which we interpret as being due to multiphonon processes in the presence of strong electron-phonon coupling (EPC). At higher energies, the orbital excitations are shown to be dressed by phonons. The high quality of the data permits a quantitative test of the analytical model for the RIXS cross section, which has been proposed to describe EPC in transition-metal oxides (TMOs). We find that the magnitude of the EPC is comparable to that found for a range of 3d TMOs. This indicates that EPC may be of equal importance in determining the phenomenology displayed by corresponding 5d-based systems.

Abstract:

the deposited package contains resistivity and x-ray diffraction data on the layered potassium-iridate materials KxIryO2 We report structural studies of the spin-orbit Mott insulator family KxIryO2, with triangular layers of edge-sharing IrO6 octahedra bonded by potassium ions. The potassium content acts as a chemical tuning parameter to control the amount of charge in the Ir-O layers. Unlike the isostructural families with Ir replaced by Co or Rh (y=1), which are metallic over a range of potassium compositions x, we instead find insulating behaviour with charge neutrality achieved via iridium vacancies, which order in a honeycomb supercell above a critical composition. By performing density functional theory calculations we attribute the observed behaviour to a subtle interplay of crystal-field environment, local electronic correlations and strong spin-orbit interaction at the Ir4+ sites, making this structural family a candidate to display Kitaev magnetism in the experimentally unexplored regime that interpolates between triangular and honeycomb structures.

Abstract:

The deposited package contains magnetic susceptibility, muon spin relaxation, powder inelastic neutron scattering and pulsed-field magnetization data of the honeycomb Kitaev magnet alpha-Li2IrO3. The readme file inside the .zip archive contains detailed information about the individual file formats in the data archive.