Speaker
Description
Experimentally, magic-angle twisted multilayer graphenes have been found to exhibit gate-tunable superconducting phases, enabling the realization of monolithic superconducting devices controlled purely by electrostatic gating. A fundamental feature of type II superconductors is the presence of vortices, whose dynamics strongly influence dissipation. We use a Josephson junction in magic-angle twisted quadruple layer graphene as a vortex sensor enabling the detection of the quantum dynamics of individual Pearl-vortices penetrating or leaving the supeconducting leads. The vortices lead to abrupt shifts in the Fraunhofer interference pattern. Time-resolved measurements allow us to investigate the dynamics of individual vortices, providing access to the characteristic vortex energy scale and the London penetration depth. Our measurements reveal a high-temperature regime dominated by classical thermal activation over an energy barrier, which crosses over at low temperatures to a regime of macroscopic quantum tunneling through the barrier.
