Unveiling Magnetic Interactions of Ruthenium Trichloride via Constraining Direction of Orbital moments: Potential Routes to Realize Quantum Spin Liquid

Understand

Recent experiments reveal that the honeycomb ruthenium trichloride {\alpha}-RuCl3 is a prime candidate of the Kitaev quantum spin liquid (QSL).

• However, there is no theoretical model which can properly describe its experimental dynamical response, due to the lack of a full understanding of its magnetic interactions.
• Here, we propose a general scheme to calculate the magnetic interactions in systems (e.g., {\alpha}-RuCl3) with non-negligible orbital moments by constraining the directions of orbital moments.
• With this scheme, we put forward a minimal J1-K1-{\Gamma}1-J3-K3 model for {\alpha}-RuCl3 and find that: (I) The third nearest neighbor (NN) antiferromagnetic Heisenberg interaction J3 stabilizes the zigzag antiferromagnetic order; (II) The NN symmetric off-diagonal exchange {\Gamma}1 plays a pivotal role in determining the preferred direction of magnetic moments and generating the spin wave gap.