Strong coupling of microwave photons to antiferromagnetic fluctuations in an organic magnet

  1. M. Mergenthaler,
  2. J. Liu,
  3. J. J. Le Roy,
  4. N. Ares,
  5. A. L. Thompson,
  6. L. Bogani,
  7. F.Luis,
  8. S. J. Blundell,
  9. T. Lancaster,
  10. A. Ardavan,
  11. G. A. D. Briggs,
  12. P. J. Leek,
  13. and E. A. Laird
Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (cQED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions. These results show that multi-spin modes in organic crystals are suitable for cQED, offering a platform for their coherent manipulation. They also utilise the cQED architecture as a way to probe spin correlations at low temperature.
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