Cavity-enhanced photo-thermoelectric response in graphene under cyclotron resonance

We investigated the photo-thermoelectric response of Landau-quantized graphene in an infrared optical cavity structure. High-quality graphene/h-BN heterostructure was fabricated on a TiO2/Au optical cavity. We observed a large enhancement of the photo-thermoelectric voltage when the energy of the inter-Landau-level optical absorption, so-called cyclotron resonance, was coincident with that of the cavity mode. This is due to cavity-enhanced cyclotron resonance absorption of mid-infrared light. A maximum photovoltage responsivity of ∼107 V/W was obtained at a wavelength of 9.27 μm under a magnetic field as low as ∼1 Tesla. The obtained responsivity was significantly higher than that of conventional graphene devices. Our results provide an efficient photo-thermoelectric conversion scheme that utilizes Landau-quantized graphene and an optical cavity.