Drastic magnetic-field-induced chiral current order and emergent current-bond-field interplay in kagome metals

Abstract

In kagome metals, the chiral current order $η$ with time-reversal-symmetry-breaking is the source of various exotic electronic states, while the method of controlling the current order and its interplay with the star-of-David bond order $ϕ$ are still unsolved. Here, we reveal that tiny uniform orbital magnetization $M[η,ϕ]$ is induced by the chiral current order, and its magnitude is prominently enlarged under the presence of the bond order. Importantly, we derive the magnetic-field ($h$)-induced Ginzburg-Landau free energy expression $ΔF[h,η,ϕ]$, which enables us to elucidate the field-induced current-bond phase transitions in kagome metals. The emergent current-bond-$h$ trilinear coupling term in the free energy, $-3m_1 hηϕ$, naturally explains the characteristic magnetic field sensitive electronic states in kagome metals, such as the field-induced current order and the strong interplay between the bond and current orders. Furthermore, we present a natural explanation for the drastic strain-induced increment of the current order transition temperature T_{TRSB} reported by a recent experiment.