Alkali superoxides differ from conventional transition metal magnets, exhibit magnetism from partially occupied oxygen molecular π∗-orbitals. Among them, CsO2 stands out for its potential to exhibit novel quantum collective phenomena, such as an orbital order induced Tomonaga-Luttinger liquid state. Using ab-initio Hubbard models, superexchange theory, and experimental spin wave measurements, we propose that CsO2 exhibits unconventional magnetoelectric characteristics at low temperature. Our analysis confirms a canted antiferromagnetic ground state and a spin-flop transition, with ferroelectricity is induced by breaking inversion and time-reversal symmetry in the spin-flop phase. Consequently, our analysis reveals a strong interplay not only between exchange interactions but also among magnetically-induced polarization and orbital order. The magnetic structure, stabilized by orbital order, induces magnetically-induced polarization through an antisymmetric mechanism. Overall, our results reveal the coexistence of three highly entangled orders in CsO2, namely, orbital, spin and ferroelectricity.
@article{arxiv.2411.06671,
title = {Entangled orbital, spin, and ferroelectric orders in $p$-electron magnet CsO$_2$},
author = {Ryota Ono and Ravi Kaushik and Sergey Artyukhin and Martin Jansen and Igor Solovyev and Russell A. Ewings},
journal= {arXiv preprint arXiv:2411.06671},
year = {2024}
}