Discovery of charge order above room-temperature in the prototypical kagome superconductor La(Ru1−xFex)3Si2

Abstract

The kagome lattice is an intriguing and rich platform for discovering, tuning and understanding the diverse phases of quantum matter, crucial for advancing modern and future electronics. Despite considerable efforts, accessing correlated phases at room temperature has been challenging. Using single-crystal X-ray diffraction, we discovered charge order above room temperature in La(Ru_1−xFe_x)₃Si₂ (x = 0, 0.01, 0.05), where charge order related to out-of-plane Ru atom displacements appears below T_CO,I  ≃ 400 K. The secondary charge ordered phase emerges below T_CO,II  ≃ 80–170 K. Furthermore, first principles calculations reveal both the kagome flat band and the van Hove point near the Fermi energy in LaRu₃Si₂, driven by Ru-dz² orbitals. Our results identify LaRu₃Si₂ as the kagome superconductor with the highest known charge ordering temperature, offering a promising avenue for researching room temperature quantum phases and developing related technologies.

The study focuses on the charge order in LaRu3Si2, a material with a kagome lattice structure, discovering a charge-ordered state that persists at or above room temperature. This finding classifies LaRu3Si2 as the kagome superconductor with the highest charge ordering temperature, suggesting potential for applications in devices operating at normal environmental conditions without the need for cooling.