Enhanced Magnetism and Phase Transitions in Ultrathin Quantum Spin Liquid Na2IrO3 Flakes

Abstract

The quest for quantum spin liquids has garnered significant attention due to their rich physics and disruptive prospects in quantum communication and computation. Spin-orbit coupling, electron correlation, and structural distortion play critical roles in the candidate materials that eventually order antiferromagnetically at low temperatures. We introduce quantum electron confinement to the existing complexity and explore the interplay between Heisenberg and Kitaev interactions in ultrathin \ce{Na2IrO3} layers using first-principles calculations. The zigzag antiferromagnetic state in the monolayer is reinforced and pushed further away from the Kitaev spin liquid state due to the increased strength of Heisenberg and off-diagonal exchange interactions. In contrast, the carrier-doped flakes undergo a Mott insulator-to-metal transition accompanied by an antiferromagnetic to ferromagnetic transition. These findings present exciting prospects for comprehending magnetism in a novel two-dimensional framework of non-van der Waals correlated oxide flakes.