Exploring the coupling of Mott insulators to elastic degrees of freedom by pressure tuning

Elena GATI

Organic charge-transfer salts are considered as prime examples to study the wealth of phenomena that arise from strong electronic correlations, given their large tunability that makes their intriguing physics accessible in laboratory settings. In recent years, it also became clear that they are ideal candidate systems to explore the role of electron-lattice coupling in correlated materials, since they are very amenable to pressure tuning. For example, we demonstrated that the universal properties of the pressure-driven Mott metal-insulator transition in -(BEDT-TTF)2Cu[N(CN)2]Cl are governed by “critical elasticity”, i.e., the coupling of the critical electronic subsystem to the crystal lattice [1].
After reviewing these results on the organic charge-transfer salts, I will focus on manifestations of electron-lattice coupling in inorganic materials, that are revealed by pressure tuning [2], in the main part of my talk. Specifically, I will discuss the example case of ferromagnetism in the Mott insulator VI3 in which hydrostatic pressure stabilizes symmetry-breaking structural distortions that are responsible for a doubling of the ferromagnetic transition temperature by the application of moderate hydrostatic pressures [3]. I will also introduce how modern uniaxial pressure devices, that can be used to deliberately break symmetry, allow to determine the elastocaloric effect [4]- a quantity that is a direct manifestation of electron-lattice-coupling - and discuss its applicability for the study of strongly correlated Mott insulators in the future.

[1] E. Gati et al., Science Advances 2, 1601646 (2016)
[2] E. Gati et al., Annalen der Physik 532, 2000248 (2020)
[3] E. Gati et al., Phys. Rev. B 100, 094408 (2019) (Editor's Suggestion)
[4] M. Ikeda et al., Rev. Sci. Inst. 90, 083902 (2019)