Correlation-driven orbital altermagnetism in kagome materials

Altermagnetism describes a broad class of magnetically ordered phases that display zero magnetization, time-reversal symmetry breaking, and nodal d-wave (or higher angular momentum) spin-splitting. While many studies have focused on ordering in the spin degrees of freedom, here we show that metallic kagome-based materials can realize orbital altermagnetism, owing to the existence of van Hove singularities (vHs) in the kagome band structure. Such a state emerges from the interplay of two common instabilities associated with the vHs, namely, bond order and loop-current order. We use a low-energy microscopic model to show that certain combinations of bond and loop-current orders can generate altermagnetism. We propose that the AV3Sb5 kagome metals, which are known to display complex charge-order patterns, are strong candidates to display orbital altermagnetism.