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arXiv · 2207.00365

Superexchange and spin-orbit coupling in monolayer and bilayer chromium trihalides

Kok Wee Song·Vladimir I Fal'ko
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Abstract

We build a microscopic model to study the intra- and inter-layer superexchange due to electrons hopping in chromium trihalides ($\mathrm{CrX}_3$, X= Cl, Br, and I). In evaluating the superexchange, we identify the relevant intermediate excitations in the hopping. In our study, we find that the intermediate hole-pairs excitations in the $p$-orbitals on X ion play a crucial role in mediating various types of exchange interactions. In particular, the inter-layer antiferromagnetic exchange may be realized by the hole-pair-mediated superexchange. Interestingly, we also find that these virtual hopping processes compete with each other leading to weak intra-layer ferromagnetic exchange. In addition, we also study the spin-orbit coupling effects on the superexchange and investigate the Dzyaloshinskii-Moriya interaction. Finally, we extract the microscopic model parameters from density functional theory for analyzing the exchange interactions in a monolayer $\mathrm{CrI}_3$.

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Kok Wee Song, Vladimir I Fal'ko. 2022-07-01. Superexchange and spin-orbit coupling in monolayer and bilayer chromium trihalides. https://doi.org/10.1103/physrevb.106.245111

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