Abstract
We present a combined study of thermal expansion and resistance fluctuation spectroscopy measurements exploring the static and dynamic aspects of the charge-glass formation in the quasi-two-dimensional organic conductors with = Cs and = Co,Zn. In these materials, the emergence of a novel charge-glass state so far has been interpreted in purely electronic terms by considering the strong frustration of the Coulomb interactions on a triangular lattice. Contrary to this view, we provide comprehensive evidence for the involvement of a structural glasslike transition at . This glassy transition can be assigned to the freezing of structural conformations of the ethylene endgroups in the donor molecule with an activation energy of , and the concomitant slowing down of the charge-carrier dynamics is well described by a model of nonexponential kinetics. These findings disclose an important aspect of the phase diagram and calls for revisiting the present views of the glassy dynamics in the whole family of . Our results suggest that the entanglement of slow structural and charge-cluster dynamics due to the intimate coupling of lattice and electronic degrees of freedom determine the charge-glass formation under geometric frustration.
- Received 1 September 2021
- Revised 3 December 2021
- Accepted 20 January 2022
DOI:https://doi.org/10.1103/PhysRevB.105.L041114
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