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

Gati, Elena; Garst, Markus; Manna, Rudra S.; Tutsch, Ulrich; Wolf, Bernd; Bartosch, Lorenz; Schubert, Harald; Sasaki, Takahiko; Schlueter, John A.; Lang, Michael

##### Abstract:
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 ΔL/L as a function of continuously controlled helium-gas pressure P for the organic conductor κ-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl across the pressure-induced Mott transition. We observe strongly nonlinear variations of ΔL/L 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.

 Zugehörige Institution(en) am KIT Institut für Theoretische Festkörperphysik (TFP) Publikationstyp Zeitschriftenaufsatz Publikationsmonat/-jahr 12.2016 Sprache Englisch Identifikator ISSN: 2375-2548 KITopen-ID: 1000128938 Erschienen in Science advances Verlag American Association for the Advancement of Science (AAAS) Band 2 Heft 12 Seiten Art.-Nr.: e1601646 Vorab online veröffentlicht am 07.12.2016 Schlagwörter Strongly correlated electron systems, Mott metal-insulator transiton, critical phenomena, thermodynamic studies, thermal expansion, organic charge-transfer salts, effects of hydrostatic pressure, coupling of electrons to lattice degrees of freedom Nachgewiesen in Web of ScienceScopus
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