First-Principles Investigation of Orbital Magnetization and Loop Currents in CsV₃Sb₅ Kagome Metal

The AV₃Sb₅ (A = K, Rb, Cs) family of kagome metals was recently discovered to host a charge density wave (CDW) state that may also break time reversal symmetry (TRS). Due to lack of spin order in this phase, the TRS breaking has been proposed to result from electron interaction-induced orbital magnetism, potentially manifesting as loop currents. However, evidence for the orbital magnetism remains inconclusive. It is further unclear whether it arises (if at all) from electronic currents localized around atomic sites, or from those of itinerant character - the latter being conducive to a loop current state. To explore these questions, we apply the modern theory of orbital magnetization to a Wannierized tight-binding model of the CDW state of CsV₃Sb₅ derived from first-principles density functional theory. We induce orbital magnetism by introducing complex phase twists to hopping amplitudes, equivalent to applying a magnetic flux, and compute the susceptibility to the various twists to identify the leading loop-current instability. Finally, we decompose the resulting orbital magnetization into gauge-invariant, and thus in-principle observable, local and itinerant contributions to reveal the microscopic character of the emergent orbital magnetism.