Kitaev-Heisenberg-J2-J3 model for the iridates A2IrO3

TL;DR

This paper introduces a comprehensive model combining Kitaev and Heisenberg interactions with additional couplings to describe the magnetic properties of layered iridates, revealing a complex phase diagram consistent with experimental observations.

Contribution

It proposes a new J-Kitaev-Heisenberg-J2-J3 model that captures the magnetic phases of A2IrO3 iridates, emphasizing the importance of farther neighbor interactions.

Findings

Rich classical phase diagram including zigzag and stripy phases

Parameter estimates consistent with experimental magnetic order

Necessity of including both Kitaev and farther neighbor couplings

Abstract

A Kitaev-Heisenberg-J2-J3 model is proposed to describe the Mott-insulating layered iridates A2IrO3 (A=Na,Li). The model is a combination of the Kitaev honeycomb model and the Heisenberg model with all three nearest neighbor couplings J1, J2 and J3. A rich phase diagram is obtained at the classical level, including the experimentally suggested zigzag ordered phase; as well as the stripy phase, which extends from the Kitaev-Heisenberg limit to the J1-J2-J3 one. Combining the experimentally observed spin order with the optimal fitting to the uniform magnetic susceptibility data gives an estimate of possible parameter values, which in turn reaffirms the necessity of including both the Kitaev and farther neighbor couplings.