Electron-phonon coupling of epigraphene at millikelvin temperatures measured by quantum transport thermometry

We investigate the basic charge and heat transport properties of charge neutral epigraphene at sub-kelvin temperatures, demonstrating a nearly logarithmic dependence of electrical conductivity over more than two decades in temperature. Using graphene's sheet conductance as an in situ thermometer, we present a measurement of electron-phonon heat transport at mK temperatures and show that it obeys the T4 dependence characteristic for a clean two-dimensional conductor. Based on our measurement, we predict the noise-equivalent power of ∼ 10 − 22 W / Hz of the epigraphene bolometer at the low end of achievable temperatures.