Prominent Intrinsic Orbital Hall Effect in the 135 Kagome Metal Family and Orbital Responses in the Loop-Current Phase

Abstract

The study of electronic orbital degrees of freedom, including the generation and control of orbital currents and orbital angular momentum, has emerged as a vibrant research field. Here, we study the orbital Hall effect (OHE), one of the key mechanisms for orbital current generation, in transition-metal kagome-lattice metals. We propose a large positive OHE in CsTi${}_3$Bi${}_5$ and negative OHEs in CsV${}_3$Sb${}_5$ and CsCr${}_3$Sb${}_5$ models. Orbital-sector decomposition shows that the $|l_d^z|=2$ $d$-orbital channel gives a positive contribution, whereas the $|l^z|=1$ $d$- and $p$-orbital channels can give negative contributions. Control calculations suggest a persistent orbital-sector sign tendency near the actual filling, while strong $p$-$d$ hybridization modulates the quantitative balance and total OHE sign. Thus, the compound and filling dependence of the OHE reflects both the sign tendency of each orbital sector and the hybridization-controlled balance among them. Furthermore, we investigate the loop-current phase of CsV${}_3$Sb${}_5$ and show that it induces finite local atomic orbital angular momentum. We also show that loop-current-related symmetry lowering allows finite symmetric components of the orbital conductivity tensor. This study provides a basis for exploring orbital currents and local orbital-angular-momentum responses in strongly correlated kagome metals.

15 pages, 12 figures