2026/07/30 by Xiuhua Chen, Yilin Wang
Physics and Astronomy · #cond-mat.str-el #cond-mat.mtrl-sci
5 pages, 4 figures
arxiv created 2026/07/30 · arxiv updated 2026/07/31
Altermagnet CsCr2S2O undergoes a Verwey-type metal-to-insulator transition (MIT) driven by lattice distortion and a stripe charge order on the Cr sublattice, reminiscent of the physics in Fe3O4. However, atomic distortions occur exclusively at the ligand sites rather than the Cr sites. What drives such a pronounced charge imbalance between Cr sites thus remains a mystery. Utilizing DFT+DMFT calculations, we identify an orbital-selective Mott transition, which leaves the correlated metallic dyz orbital governing the low-energy physics. We demonstrate that S-site distortions trigger an initial, tiny charge asymmetry between Cr sites via Cr-dyz and S-p orbital hybridization. Crucially, this asymmetry is significantly amplified by dynamical electronic correlations, resulting in a large discrepancy in both the charge and electron correlations of the Cr-dyz orbital between distinct Cr sites. This further induces a substantial differentiation in local spin polarizations in the altermagnetic state, ultimately driving the MIT. In contrast, we predict that replacing S with Te weakens this correlation-amplification effect and fails to induce an MIT due to weaker electron correlations. Our findings demonstrate that many-body effects can drastically amplify ligand instabilities to reshape the electronic structure of altermagnets, highlighting that ligand engineering is of paramount importance for realizing robust metallic altermagnetism.