Bowen Yang, Yin Min Goh, Suk Hyun Sung, Gaihua Ye, Sananda Biswas, David A. S. Kaib, Ramesh Dhakal, Shaohua Yan, Chenghe Li, Shengwei Jiang, Fangchu Chen, Hechang Lei, Rui He, Roser Valentí, Stephen M. Winter, Robert Hovden, Adam W. Tsen
- Layered {\alpha}-RuCl3 is a promising material to potentially realize the long-sought Kitaev quantum spin liquid with fractionalized excitations. While evidence of this exotic state has been reported under a modest in-plane magnetic field, such behavior is largely inconsistent with theoretical expectations of Kitaev phases emerging only in out-of-plane fields. These predicted field-induced states have been mostly out of reach due to the strong easy-plane anisotropy of bulk crystals, however. We use a combination of tunneling spectroscopy, magnetotransport, electron diffraction, and ab initio calculations to study the layer-dependent magnons, anisotropy, structure, and exchange coupling in atomically thin samples. Due to structural distortions, the sign of the average off-diagonal exchange changes in monolayer {\alpha}-RuCl3, leading to a reversal of magnetic anisotropy to easy-axis. Our work provides a new avenue to tune the magnetic interactions in {\alpha}-RuCl3 and allows theoretically predicted quantum spin liquid phases for out-of-plane fields to be more experimentally accessible.
