Tatjana THOMAS
The organic conductors -(ET)2MM’(SCN)4 have become of particular interest due to the development of a non-equilibrium charge-glass (CG) state when the charge-ordering (CO) transition is kinetically avoided by fast cooling [1,2]. In thermal equilibrium, i.e. for slow cooling, CO results from strong onsite and intersite Coulomb interactions. Therefore, the quenched state has been discussed to be a consequence of the geometric frustration of charges on a triangular lattice, which hinders long-range order. This interpretation of a purely electronic mechanism has been currently challenged by the discovery of a structural glass transition in highly frustrated -CsM’ with M’=Zn,Co [3], which always exhibit a CG state on experimental time scales.
Fluctuation spectroscopy has proven to be a powerful tool to study the charge carrier dynamics at low frequencies [4], which have shown to become very slow and heterogeneous when approaching the glass transition from above, similar to conventional glass-forming liquids [1,5]. Here, we present extended and systematic noise studies on three compounds MM’=CsCo, RbZn, TlZn with varying degree of frustration in different charge states by using different thermal protocols. From the power spectral density, we extract characteristic energies dominating the resistance noise and compare the results with the quenched states. We will discuss the interplay of charge and lattice dynamics and the observed enhancement of slow fluctuations at the CO phase transition.
[2] Kagawa and Oike, Adv. Mater. 29, 1601979 (2017)
[3] Thomas/Saito et al., arXiv:2109.00811 (2021)
[4] Müller and Thomas, Crystals 8, 166 (2018)
[5] Sasaki et al., Science 357, 1381 (2017)