Charge orders with distinct magnetic response in a prototypical kagome superconductor LaRu${}_3$Si${}_2$

Abstract

The kagome lattice has emerged as a promising platform for hosting unconventional chiral charge order at high temperatures. Notably, in LaRu${}_3$Si${}_2$, a room-temperature charge-ordered state with a propagation vector of ($\frac{1}{4}$,~0,~0) has been recently identified. However, understanding the interplay between this charge order and superconductivity, particularly with respect to time-reversal-symmetry breaking, remains elusive. In this study, we employ single crystal X-ray diffraction, magnetotransport, and muon-spin rotation experiments to investigate the charge order and its electronic and magnetic responses in LaRu${}_3$Si${}_2$ across a wide temperature range down to the superconducting state. Our findings reveal the emergence of a charge order with a propagation vector of ($\frac{1}{6}$,~0,~0) below $T_{\mathrm{CO},2}$ $\simeq$ 80 K, coexisting with the previously identified room-temperature primary charge order ($\frac{1}{4}$,~0,~0). The primary charge-ordered state exhibits zero magnetoresistance. In contrast, the appearance of the secondary charge order at $T_{\mathrm{CO},2}$ is accompanied by a notable magnetoresistance response and a pronounced temperature-dependent Hall effect, which experiences a sign reversal, switching from positive to negative below $T^{\ast }$ $\simeq$ 35 K. Intriguingly, we observe an enhancement in the internal field width sensed by the muon ensemble below $T^{\ast }$ $\simeq$ 35 K. Moreover, the muon spin relaxation rate exhibits a substantial increase upon the application of an external magnetic field below $T_{\mathrm{CO},2}$ $\simeq$ 80 K. Our results highlight the coexistence of two distinct types of charge order in LaRu${}_3$Si${}_2$ within the correlated kagome lattice, namely a non-magnetic charge order ($\frac{1}{4}$,~0,~0) below $T_{\mathrm{co},1}$ $\simeq$ 400 K and a time-reversal-symmetry-breaking charge order below $T_{\mathrm{CO},2}$.

10 pages, 5 figures