First-order phase transitions produce abrupt changes to the character of both ground and excited electronic states. Here we conduct electronic compressibility measurements to map the spin phase diagram and Landau level (LL) energies of monolayerin a magnetic field. We resolve a sequence of first-order phase transitions between completely spin-polarized LLs and states with LLs of both spins. Unexpectedly, the LL gaps are roughly constant over a wide range of magnetic fields below the transitions, which we show reflects spin-polarized ground states with opposite spin excitations. These transitions also extend into compressible regimes, with a sawtooth boundary between full and partial spin polarization. We link these observations to the important influence of LL filling on the exchange energy beyond a smooth density-dependent contribution. Our results show thatrealizes a unique hierarchy of energy scales where such effects induce reentrant magnetic phase transitions tuned by density and magnetic field.
Electronic structure of Co 3d states in the Kitaev material candidate honeycomb cobaltate Na3Co2SbO6 probed with x-ray dichroism
The recent prediction that honeycomb lattices of Co2+ (3d7) ions could host dominant Kitaev interactions
provides an exciting direction for exploration of new routes to stabilizing Kitaev’s quantum spin liquid in
real materials. Na3Co2SbO6 has been singled out as a potential material candidate provided that spin and
orbital moments couple into a Jeff = 1/2 ground state, and that the relative strength of trigonal crystal field
and spin-orbit coupling acting on Co ions can be tailored. Using x-ray linear dichroism (XLD) and x-ray
magnetic circular dichroism (XMCD) experiments, alongside configuration interaction calculations, we confirm
the counterintuitive positive sign of the trigonal crystal field acting on Co2+ ions and test the validity of the
Jeff = 1/2 description of the electronic ground state. The results lend experimental support to recent theoretical predictions that a compression (elongation) of CoO6 octahedra along (perpendicular to) the trigonal axis would drive this cobaltate toward the Kitaev limit, assuming the Jeff = 1/2 character of the electronic ground state is preserved.
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- Award ID(s):
- 2104881
- NSF-PAR ID:
- 10488387
- Publisher / Repository:
- DOE Pages
- Date Published:
- Journal Name:
- Physical Review B
- Edition / Version:
- 1
- Volume:
- 107
- Issue:
- 21
- ISSN:
- 2469-9950
- Subject(s) / Keyword(s):
- High pressure, Kitaev materials, x-ray spectroscopy, spin liquid
- Format(s):
- Medium: X Size: 1.2MB Other: pdf
- Size(s):
- 1.2MB
- Sponsoring Org:
- National Science Foundation
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