Anomalous and Anisotropic Nonlinear Susceptibility in the Proximate Kitaev Magnet $\alpha$-RuCl${}_3$

Ludwig Holleis, Joseph Prestigiacomo, Zhijie Fan +5

The leading order nonlinear (NL) susceptibility, ${\chi }_3$, in a paramagnet is negative and diverges as $T\to 0$. This divergence is destroyed when spins correlate and the NL…