Correlated order at the tipping point in the kagome metal CsV₃Sb₅

Spontaneously broken symmetries are at the heart of many phenomena of quantum matter. However, determining the exact symmetries broken can be challenging due to experimental imperfections, such as misalignment of principle crystalline axis, irregularity of device geometry and non-uniform strain distribution. Focused-ion-beam is an ideal micro-fabrication tool with high precision which allows us to minimize these extrinsic imperfections, rendering the exploration of intrinsic electronic symmetries possible. The particular material under the spot light is the Kagome superconductor CsV₃Sb₅, where electronic correlations result in a cascade of charge ordered phases [1], leading to possible spontaneous symmetry breaking with chiral electronic states [2,3].

Using FIB technique, we successfully fabricated hexagon-shaped devices with high precision [4]. Great care was taken to align the structure with the in-plane lattice vectors (<0.5 deg) and to minimize shape deviations to avoid any symmetry lowering due to the structure's shape itself. The directional in-plane electric transport unambiguously reveals that the in-plane C6 rotational symmetry remains intact down to cryogenic temperatures. Moreover, the spontaneous symmetry breaking occurs only when external perturbations, such as magnetic field and uniaxial strain, are included. Our results provide a unifying picture for the controversial charge order in Kagome metals and highlight the need for microscopic materials control in the identification of broken symmetries.



[1] He Zhao et al., Cascade of correlated electron states in the kagome superconductor CsV₃Sb₅; Nature 599, 216(2021).

[2] Chunyu Guo et al., Switchable chiral transport in charge-ordered kagome metal CsV₃Sb₅; Nature 611, 461(2022)

[3] Yishuai Xu et al., Three-state nematicity and magneto-optical Kerr effect in the charge density waves in kagome superconductors; Nature Physics 18, 1470 (2022).

[4] Chunyu Guo et al., Correlated order at the tipping point in the kagome metal CsV3Sb5 Nature Physics 20, 579 (2024).