Emergent photo-thermoelectricity in localized bulk quantum Hall state of graphene

We demonstrate the generation of photovoltage from localized bulk quantum Hall states (QHS) of graphene. Using a graphene device with an inner contact geometry, conduction through the quantum Hall edge state was eliminated, enabling detection of the photovoltaic response of the bulk QHS. A photoresponse was detected under inter-Landau-level optical absorption of mid-infrared light. We found that the photovoltage in the inner contact device was generated only when graphene was in a QHS, where transport of the device is due to the bulk QHS. These results suggest an emergence of the photo-thermoelectric effect in the localized bulk QHS.