Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O9

We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5+ (5d(4)) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J = 0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK

Structural and electronic characterisation of Cu/Au(111) near-surface alloys (dataset)

Geometrical structure and electronic characteristics of ultrathin metallic films of one metal on another are strongly influenced by factors such as lattice mismatch and formation of near-surface alloys. Doped systems often show modified chemical-physical properties which may be amenable to different reactivity routes. Copper-gold surface alloys have received the attention of several studies, only a few of which have been undertaken in an UHV environment, using surface sensitive techniques. In this contribution, systems produced upon room temperature deposition of copper on the (22×√3)-Au(111) surface, at various copper loadings and annealed to different temperatures, are investigated using scanning tunnelling microscopy and synchrotron radiation based techniques (X-ray photoelectron diffraction, photoemission), with comparison with some theoretical modelling. Overall the fcc lattice is essentially maintained on preparation. Upon thermal treatments structural and compositional changes, in favour of alloyed structures with tetragonal packing, are seen. The data underpinning this publication are part of a PhD research project and will be released upon completion of the project, 202