Quantum Criticality of Granular Sachdev-Ye-Kitaev Matter

We consider granular quantum matter defined by Sachdev-Ye-Kitaev dots coupled via random one-body hopping. Within the framework of Schwarzian field theory, we identify a zero-temperature quantum phase transition between an insulating phase at weak and a metallic phase at strong hopping. The critical hopping strength scales inversely with the number of degrees of freedom on the dots. The increase of temperature out of either phase induces a crossover into a regime of strange metallic behavior.