Dr Yikai Yang (University of Oxford)
By strongly hybridizing a high-finesse re-entrant cavity with an archetypal Ising magnet, LiHoF4, we perform microwave spectroscopic measurements on the electro-nuclear spin excitation spectra of the latter at dilution temperatures and high magnetic fields. We derive an explicit microscopic expression of the direct experimental observation by combining linear response theory [1] and the input-output formalism [2], without resorting to semi-classical approximations. With further help from mean field calculations of the eigen-states of LiHoF4, both with and without the random phase approximations, we obtain quantitative agreement between theoretical and experimental results across a wide range of parameter space. While the results provide strong support for existing hypotheses [3, 4] about the critical behavior of LiHoF4, they also reveal further mysteries regarding such a system that was previously considered well understood.
References:
1. J. Jensen. Rare Earth Magnetism (1991)
2. P. Meystre, M. Sargent, Elements of Quantum Optics (2007) 3. H. M. Ronnow, et al. Science, 5720, 308 (2005)
4. R. D. McKenzie, et al. Phys. Rev. B, 97, 214430 (2018)
