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arXiv · 2411.06671

Entangled orbital, spin, and ferroelectric orders in $p$-electron magnet CsO$_2$

Ryota Ono·Ravi Kaushik·Sergey Artyukhin·Martin Jansen·Igor Solovyev·Russell A. Ewings
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Abstract

Alkali superoxides differ from conventional transition metal magnets, exhibit magnetism from partially occupied oxygen molecular $\pi^*$-orbitals. Among them, CsO$_2$ 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 CsO$_2$ 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 CsO$_2$, namely, orbital, spin and ferroelectricity.

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Ryota Ono, Ravi Kaushik, Sergey Artyukhin, Martin Jansen, Igor Solovyev, Russell A. Ewings. 2024-11-11. Entangled orbital, spin, and ferroelectric orders in $p$-electron magnet CsO$_2$. https://arxiv.org/abs/2411.06671

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