Hot Carrier Thermalization and Josephson Inductance Thermometry in a Graphene-based Microwave Circuit

Abstract: Due to its exceptional electronic and thermal properties, graphene is a key material for bolometry, calorimetry, and photon detection. However, despite graphene's relatively simple electronic structure, the physical processes responsible for the transport of heat from the electrons to the lattice are experimentally still elusive. Here, we measure the thermal response of low-disorder graphene encapsulated in hexagonal boron nitride (hBN) by integrating it within a multi-terminal superconducting device coupled to a microwave resonator. This technique allows us to simultaneously apply Joule heat power to the graphene flake while performing calibrated readout of the electron temperature. We probe the thermalization rates of both electrons and holes with high precision and observe a thermalization scaling exponent consistent with cooling dominated by resonant electron-phonon coupling processes occurring at the interface between graphene and superconducting leads. The technique utilized here is applicable for wide range of semiconducting-superconducting interface heterostructures and provides new insights into the thermalization pathways essential for the next-generation thermal detectors.