Cavity control of multiferroic order in single-layer NiI$_2$

TL;DR

This paper proposes using cavity control to modify magnetic interactions in single-layer NiI$_2$, demonstrating that even small cavity effects can alter magnetic order and potentially induce phase transitions.

Contribution

It introduces a novel approach to observe cavity vacuum effects in magnetic systems through spiral magnetism in NiI$_2$, highlighting a feasible experimental platform.

Findings

Decreasing substrate distance alters exchange interactions in NiI$_2$

Cavity effects can change spiral wavelength and induce magnetic phase transitions

Proposes a realistic setup for observing cavity vacuum effects in magnetic materials

Abstract

Controlling materials through their interactions with electromagnetic vacuum fluctuations is an emergent frontier in material engineering. Although recent experiments have demonstrated dark cavity effects for electronic material phases, like superconductivity, ferroelectricity and charge density waves, a smoking gun experiment for magnetic systems is lacking. Largely, this comes from the focus on phase transitions, where a large critical light-matter coupling is needed to observe cavity modifications. Here, we propose spiral magnets, where even a small cavity-mediated change in magnetic interactions is reflected in a change of the spiral wavelength, as a promising platform to observe cavity effects. We focus on the single-layer multiferroic NiI$_2$, interacting with electric field fluctuations from surface phonon polaritons of the paraelectric substrate SrTiO$_3$. With decreasing substrate-material distance, the ratio of nearest and third nearest neighbor exchange interactions reduces, leading to an increase of the spiral wavelength and an eventual transition into a ferromagnetic state. Our work identifies a realistic platform to observe cavity vacuum renormalization effects in magnetic systems.