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Abstract:
The 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. In solid state materials, changes in the crystal lattice are often accompanied by changes in the electronic system. Whether the lattice or the electrons is the primary driver of a transition may, however, be difficult to ascertain. Noad et al. measured the Young?s modulus in the extremely clean material Sr2RuO4 as it underwent an electronic (Lifshitz) transition. The researchers found a large drop in the Young?s modulus at the transition, suggesting that conduction electrons drive a nonlinear elastic response in this material. ?Jelena Stajic Measurements of the Young?s modulus revealed a lattice softening much larger than that predicted by Lifshitz.
