Charge-loop current order and Z3 nematicity mediated by bond order fluctuations in kagome metals

Abstract

Recent experiments on geometrically frustrated kagome metal AV3Sb5 (A = K, Rb, Cs) have revealed the emergence of the charge loop current (cLC) order near the bond order (BO) phase. However, the origin of the cLC and its interplay with other phases have been uncovered. Here, we propose a novel mechanism of the cLC state, by focusing on the BO phase common in kagome metals. The BO fluctuations in kagome metals, which emerges due to the Coulomb interaction and the electron-phonon coupling, mediate the odd-parity particle-hole condensation that gives rise to the topological current order. Furthermore, the predicted cLC+BO phase gives rise to the Z3-nematic state in addition to the giant anomalous Hall effect. The present theory predicts the close relationship between the cLC, the BO, and the nematicity, which is significant to understand the cascade of quantum electron states in kagome metals. The present scenario provides a natural understanding.

Tuning charge density wave of kagome metal ScV6Sn6

“…The presence of an additional valence electron in Cr results in an upward shift of the E F by 120 meV [26]. This shift also causes the vHS to move further away from the E F , where the vHS is the primary reason for the loop current order in AV 3 Sb 5 systems [39][40][41][42].…”

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

“…Theoretically, the BO and the current order emerge in the presence of sizable off-site electron correlations in Fe-based and cuprate superconductors ( 26 – 34 ) and in kagome metals ( 7 – 9 , 11 , 35 – 39 ). Notably, strong off-site interaction (due to the off-site Coulomb repulsion or the BO fluctuations) gives rise to the charge current order ( 8 – 10 , 35 ).…”

“…Theoretically, the BO and the current order emerge in the presence of sizable off-site electron correlations in Fe-based and cuprate superconductors ( 26 – 34 ) and in kagome metals ( 7 – 9 , 11 , 35 – 39 ). Notably, strong off-site interaction (due to the off-site Coulomb repulsion or the BO fluctuations) gives rise to the charge current order ( 8 – 10 , 35 ). Based on the GL free-energy analysis, interesting bond + current nematic ( ) coexisting phases have been discussed in two-dimensional (2D) and three-dimensional (3D) models ( 9 , 35 , 37 – 39 ).…”

“…Notably, strong off-site interaction (due to the off-site Coulomb repulsion or the BO fluctuations) gives rise to the charge current order ( 8 – 10 , 35 ). Based on the GL free-energy analysis, interesting bond + current nematic ( ) coexisting phases have been discussed in two-dimensional (2D) and three-dimensional (3D) models ( 9 , 35 , 37 – 39 ). Experimentally, the nematic state is actually observed by the elastoresistance ( 40 ), the scanning birefringence ( 18 ), and the STM ( 4 ) measurements.…”

“…In the present study of , we mainly focus on the current order in the -orbital (in -representation) of V ion, which has been intensively studied previously ( 7 – 10 , 35 ). However, other -orbitals (especially -, -, -orbitals) also form the large Fermi surfaces (FSs) with the van-Hove singularity (vHS) points near the Fermi level.…”