Among strongly correlated states of matter, spin liquids stand as one of the best understood theoretically but the least understood experimentally. In RuCl$_3$, inelastic neutron scattering and Raman spectroscopy reveal a continuum of excitations that persist to high temperature, in accordance with Kitaev's prediction for a spin liquid state on a honeycomb lattice. However, the effects of high magnetic fields - comparable to the spin exchange energy scale - have not been explored. Here we report measurements of the magnetotropic coefficient - the second derivative of the free energy with respect to magnetic field orientation - over a wide range of magnetic fields and temperatures. Unlike conventional spin systems, which polarize and become isotropic at high fields, the magnetization in RuCl$_3$ shows no signs of saturation up to 65 Tesla. Furthermore, temperature and magnetic field compete to determine the magnetic response in a way that is independent of the large exchange energy. This scale-invariant magnetic response is a new signature of the spin-liquid state that goes beyond current predictions of the Kitaev model.
Modic KA, McDonald RD, Ruff JPC, et al. Scale-invariance of a spin liquid in high magnetic fields. arXiv:190109245.
Modic, K. A., McDonald, R. D., Ruff, J. P. C., Bachmann, M. D., Lai, Y., Palmstrom, J. C., … Shekhter, A. (n.d.). Scale-invariance of a spin liquid in high magnetic fields. ArXiv:1901.09245. ArXiv.
Modic, Kimberly A, Ross D. McDonald, J. P. C. Ruff, Maja D. Bachmann, You Lai, Johanna C. Palmstrom, David Graf, et al. “Scale-Invariance of a Spin Liquid in High Magnetic Fields.” ArXiv:1901.09245. ArXiv, n.d.
K. A. Modic et al., “Scale-invariance of a spin liquid in high magnetic fields,” arXiv:1901.09245. ArXiv.
Modic KA, McDonald RD, Ruff JPC, Bachmann MD, Lai Y, Palmstrom JC, Graf D, Chan M, Balakirev FF, Betts JB, Boebinger GS, Schmidt M, Sokolov DA, Moll PJW, Ramshaw BJ, Shekhter A. Scale-invariance of a spin liquid in high magnetic fields. arXiv:1901.09245.
Modic, Kimberly A., et al. “Scale-Invariance of a Spin Liquid in High Magnetic Fields.” ArXiv:1901.09245, ArXiv.