Organic molecular conductors of the κ-(ET)₂X family are widely regarded as model systems for investigating electronic correlations in close proximity to the Mott transition, including unconventional superconductivity and frustrated magnetism. In these materials, (ET)₂ dimers—each contributing one electron—form a slightly anisotropic triangular lattice. Their low-energy physics is therefore commonly described by a Hubbard model with two hopping parameters, t and t′.

This structural motif naturally suggests that anisotropic strain, which enables controlled tuning of the anisotropy ratio t′/t, provides a powerful means to manipulate the physical properties of these compounds, including the superconducting transition temperature Tc or the superconducting order parameter.

In this talk, I will demonstrate that large anisotropic strains can now be applied even to fragile organic conductors using newly developed piezo-driven strain devices. Taking the spin-liquid candidate κ-(ET)₂Cu₂(CN)₃ as a representative example [1], I will show that strain-induced changes in anisotropy of up to ~25% allow access to extended regions of the phase diagram that were previously unreachable. In particular, we find that the recently reported spin gap in κ-(ET)₂Cu₂(CN)₃ remains robust even when the triangular lattice is tuned toward the isotropic limit. These results open a direct route to systematically exploring the role of geometric frustration in correlated electron systems in organic conductors.

[1] Lieberich et al, Science Advances, 2025