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

See allHide authors and affiliations

Science Advances  07 Dec 2016:
Vol. 2, no. 12, e1601646
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 ΔL/L as a function of continuously controlled helium-gas pressure P for the organic conductor κ-(BEDT-TTF)2Cu[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.

  • 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

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

View Full Text