H. M. L. NoadK. IshidaYOU-SHENG LIE. GatiV. StangierN. KikugawaD. A. SokolovM. NicklasB. KimI. I. MazinM. GarstJ. SchmalianA. P. MackenzieC. W. Hicks2025-01-082025-01-082023-10-27https://scholars.lib.ntu.edu.tw/handle/123456789/724664The interplay of electronic and structural degrees of freedom in solids is a topic of intense research. More than 60 years ago, Lifshitz discussed a counterintuitive possibility: lattice softening driven by conduction electrons at topological Fermi surface transitions. The effect that he predicted, however, was small and has not been convincingly observed. Using a piezo-based uniaxial pressure cell to tune the ultraclean metal strontium ruthenate while measuring the stress-strain relationship, we reveal a huge softening of the Young’s modulus at a Lifshitz transition of a two-dimensional Fermi surface and show that it is indeed driven entirely by the conduction electrons of the relevant energy band.[SDGs]SDG7journal article10.1126/science.adf3348