Abstract
In the presence of strong atomic spin-orbit coupling (SOC), tending to the coupling limit, iridates are speculated to possess a nonmagnetic singlet ground state from atomic consideration, which invariably gets masked due to different solid-state effects (e.g., hopping). Here, we try to probe the trueness of the atomic SOC-based proposal in an apparently one-dimensional system, , with well-separated ions. But all the detailed experimental as well as theoretical characterizations reveal that the ground state of is not nonmagnetic. However, our combined dc susceptibility , nuclear magnetic resonance (NMR), muon spin relaxation/rotation , and heat capacity measurements clearly refute any sign of spin freezing or ordered magnetism among the moments due to geometrical exchange frustration, while in-depth zero-field and longitudinal field investigations strongly point towards an inhomogeneous quantum spin liquid (QSL)-like ground state. In addition, the linear temperature dependence of both the NMR spin-lattice relaxation rate and the magnetic heat capacity at low temperatures suggest low-lying gapless spin excitations in the QSL phase of this material. Finally, we conclude that the effective SOC realized in iridates is unlikely to offer a ground state which will be consistent with a purely atomic coupling description.
- Received 6 July 2021
- Revised 11 March 2022
- Accepted 11 March 2022
DOI:https://doi.org/10.1103/PhysRevB.105.104431
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