Breakdown of Hooke's law of elasticity at the Mott critical endpoint in an organic conductor

• Published in: Science advances 2016-12, Vol.2 (12), p.e1601646-e1601646
• Main Authors: Gati, Elena, Garst, Markus, Manna, Rudra S, Tutsch, Ulrich, Wolf, Bernd, Bartosch, Lorenz, Schubert, Harald, Sasaki, Takahiko, Schlueter, John A, Lang, Michael
• Format: Article
• Language: English
• Subjects: Condensed Matter Physics; SciAdv r-articles; Science & Technology - Other Topics
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.1601646

The Mott metal-insulator transition, a paradigm of strong electron-electron correlations, has been considered as a source of intriguing phenomena. Despite its importance for a wide range of materials, fundamental aspects of the transition, such as its universal properties, are still under debate. We report detailed measurements of relative length changes Δ / as a function of continuously controlled helium-gas pressure for the organic conductor κ-(BEDT-TTF) Cu[N(CN) ]Cl across the pressure-induced Mott transition. We observe strongly nonlinear variations of Δ / with pressure around the Mott critical endpoint, highlighting a breakdown of Hooke's law of elasticity. We assign these nonlinear strain-stress relations to an intimate, nonperturbative coupling of the critical electronic system to the lattice degrees of freedom. Our results are fully consistent with mean-field criticality, predicted for electrons in a compressible lattice with finite shear moduli. We argue that the Mott transition for all systems that are amenable to pressure tuning shows the universal properties of an isostructural solid-solid transition.