A burning question in the emerging field of spin-orbit driven insulating iridates, such as Na2IrO3 and Li2IrO 3, is whether the observed insulating state should be classified as a Mott-Hubbard insulator derived from a half-filled relativistic j eff=1/2 band or as a band insulator where the gap is assisted by spin-orbit interaction or Coulomb correlations or both. The difference between these two interpretations is that only for the former strong spin-orbit coupling (λâ‰W, where W is the bandwidth) is essential. We have synthesized the isostructural and isoelectronic Li2RhO3 and report its electrical resistivity and magnetic susceptibility. Remarkably, it shows insulating behavior together with fluctuating effective S=1/2 moments, similar to Na2IrO3 and Li2IrO3, although in Rh4+ (4d5) the spin-orbit coupling is greatly reduced. We show that this behavior has a nonrelativistic one-electron origin (although Coulomb correlations assist in opening the gap) and can be traced to the formation of quasimolecular orbitals, similar to those in Na2IrO 3.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jul 12 2013|
ASJC Scopus subject areas
- Condensed Matter Physics
- Electronic, Optical and Magnetic Materials