The universality class of the Mott metal-insulator transition in electronic systems strongly coupled to the lattice degrees of freedom has been the subject of recent debate. While transport scaling exponents as well as a critical slowing down of resistance fluctuations point towards Ising-type criticality, a strong involvement of the lattice elasticity suggests a mean-field scenario instead. We investigate the low-frequency resistance noise in the model system $\kappa \text{−}{\left(\mathrm{ET}\right)}_2\mathrm{Cu}\left[\mathrm{N}{\left(\mathrm{CN}\right)}_2\right]\mathrm{Cl}\left(\kappa \text{−}\mathrm{Cl}\right)$—selected because it is known to exhibit critical elasticity—tuned to the Mott end point by hydrostatic pressure. Contrary to previous reports for the related, deuterated $\kappa$-Br compound, we do not find any indication of a critical slowing down, but observe a strong and anisotropic change of the relative resistance noise level in the metallic compared to the insulating phase. We speculate within the framework of isostructural criticality that a critical slowing down might emerge in the presence of structural disorder.

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• Critical phenomena
• Mott insulators
• Noise measurements
• Pressure techniques