Mode-selective electron-phonon coupling drives charge density waves in the kagome metals YRu 3 Si 2 and LaRu 3 Si 2
The study investigates why YRu3Si2 and LaRu3Si2 exhibit exceptionally high charge density wave (CDW) transition temperatures. It finds that mode-selective electron-phonon coupling, where out-of-plane Ru phonons couple to specific orbital modes, drives the CDW. Phonon anharmonicity is responsible for melting the CDW structure. Furthermore, stronger Ru-Ru bonds in YRu3Si2 enhance its higher transition temperature.