title: Breakdown of Hooke's law of elasticity at the Mott critical endpoint in an organic conductor.
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/Las a function of continuously controlled helium-gas pressurePfor the organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl across the pressure-induced Mott transition. We observe strongly nonlinear variations of ΔL/Lwith 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.
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Gati
authors.affiliation: Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany.; Institut für Theoretische Physik, Technische Universität Dresden, Zellescher Weg 17, 01062 Dresden, Germany.
authors.forename: Markus
authors.identifier: 0000-0001-5390-3316
authors.initials: M
authors.lastname: Garst
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Rudra S
authors.initials: RS
authors.lastname: Manna
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Tutsch
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Wolf
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Bartosch
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Schubert
authors.affiliation: Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Division of Materials Research, National Science Foundation, Arlington, VA 22230, USA.; Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Schlueter
authors.affiliation: Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lang
keywords: Mott metal-insulator-transiton; Strongly correlated electron systems; coupling of electrons to lattice degrees of freedom; critical phenomena; effects of hydrostatic pressure; organic charge-transfer salts; thermal expansion; thermodynamic studies