Order-by-disorder from bond-dependent exchange and intensity signature of nodal quasiparticles in a honeycomb cobaltate
Recent theoretical proposals have argued that cobaltates with edge-sharing octahedral coordination can have significant bond-dependent exchange couplings thus offering a platform in 3d ions for such physics beyond the much-explored realizations in 4d and 5d materials. Here we present high-resolution...
| Main Authors: | , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Springer Nature
2021
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| Summary: | Recent theoretical proposals have argued that cobaltates with edge-sharing octahedral coordination can have
significant bond-dependent exchange couplings thus offering a platform in 3d ions for such physics beyond the
much-explored realizations in 4d and 5d materials. Here
we present high-resolution inelastic neutron scattering
data within the magnetically ordered phase of the stacked
honeycomb magnet CoTiO3 revealing the presence of a
finite energy gap and demonstrate that this implies the
presence of bond-dependent anisotropic couplings. We
also show through an extensive theoretical analysis that
the gap further implies the existence of a quantum orderby-disorder mechanism that, in this material, crucially
involves virtual crystal field fluctuations. Our data also
provide an experimental observation of a universal winding of the scattering intensity in angular scans around
linear band-touching points for both magnons and dispersive spin-orbit excitons, which is directly related to
the non-trivial topology of the quasiparticle wavefunction in momentum space near nodal points. |
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