The interplay of electronic and structural degrees of freedom in solids is a topic of intense research. Experience and intuition suggest that structural changes drive conduction electron behavior, because the large number of valence electrons dominate the structural properties. As part of a seminal paper written over sixty years ago, Lifshitz discussed an alternative possibility: lattice softening driven by conduction electrons at topological Fermi surface transitions. The effect he predicted, however, was small, and has not been convincingly observed. Using measurements of the stress-strain relationship in the ultra-clean metal Sr2RuO4, 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 entirely driven by the conduction electrons of the relevant energy band.
@article{arxiv.2306.17835,
title = {Giant lattice softening at a Lifshitz transition in Sr$_{2}$RuO$_{4}$},
author = {Hilary M. L. Noad and Kousuke Ishida and You-Sheng Li and Elena Gati and Veronika C. Stangier and Naoki Kikugawa and Dmitry A. Sokolov and Michael Nicklas and Bongjae Kim and Igor I. Mazin and Markus Garst and Jörg Schmalian and Andrew P. Mackenzie and Clifford W. Hicks},
journal= {arXiv preprint arXiv:2306.17835},
year = {2023}
}