Crystallization and vitrification of strongly correlated electrons on a geometrically frustrated triangular lattice

We report a unique glassy state of electrons – in contrast to long-range charge ordering (CO) – realized in the organic conductor θ_m-(BEDT-TTF)₂TlZn(SCN)₄, where the lack of periodicity of the strongly correlated electrons on the triangular lattice, characterizing the glassy state, is caused by geometric frustration and strong quantum effects [1]. Our experiments reveal that the CO transition (charge crystallization) can be avoided by rapid cooling, and charge vitrification occurs via a supercooled charge-liquid state. This is accompanied by heterogeneous slow dynamics, which in turn can be understood by the notion of the energy landscape with multiple local minima. We demonstrate that the crystallization of strongly correlated electrons involves the same nucleation and growth processes as that of conventional glass-forming liquids such as structural and metallic glasses. These similarities among different classes of glass formers are surprising and will constitute further new insights to our general understanding of the liquid-glass transition.
[1] S. Sasaki, K. Hashimoto et al., Science 357, 1381–1385 (2017).