Toward realization of the Sachdev-Ye-Kitaev model in graphene

Recent theoretical studies suggest the interplay of disorder at etched graphene edges and strong Coulombs correlation enables a random all-to-all interaction between the localized charges in partially-filled Landau levels in a graphene quantum dot, providing a platform to realize the electronic Sachdev-Ye-Kitaev (SYK) model. Distinctive signatures of the underlying SYK dynamics are expected to manifest in electrical and thermoelectric transport measurements. Chaotic electronic dynamics have previously been observed in etch-defined graphene quantum dots, as a consequence of randomness of the graphene edge; however, these systems have not been investigated in the context of the SYK model. We report electric and thermoelectric transport across graphene quantum dots with suppressed Coulomb charging energy in the quantum Hall limit. Electrons are delivered by the quantum Hall edge states to the graphene quantum dot via graphene electrodes that are coupled to the dot. As the graphene quantum dot is placed in the partially-filled lowest energy Landau level, we observe a rapid decrease of electric conductance fluctuations and nearly temperature-independent thermoelectric power across the dot with increasing temperature, in agreement with the recent theoretical predictions for the SYK regime.