Reversing Néel Vector in Parity-Time Antiferromagnets by Nonreciprocal Light Scattering

Antiferromagnetic (AFM) spintronics has been receiving tremendous attention due to the ultrafast kinetics, zero stray field, immunity to external field, and potential for miniaturizing magnetic storage devices. The optical control of the AFM Néel vector has become an intriguing topic. Here, we propose a nonreciprocal light-scattering mechanism to flip the Néel vector in parity-time (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>PT</mml:mi></mml:math>) combined AFM multilayers by estimating the energy contrast between the bistable Néel polarization configurations. We illustrate our theory using a low-energy <b><i>k</i></b>·<b><i>p</i></b> model and perform <i>ab initio</i> calculations on two typical <i>A</i>-type AFM materials, MnBi₂Te₄ and CrI₃ thin films. We show that both light handedness and incident photon frequency could control the relative stability between the bistable Néel vector states. According to this theory, our parameter-independent calculations on the AFM phase diagram predict results consistent with recent experiments. This mechanism provides an effective route to controlling the AFM order through ultrafast photomagnetic interactions.