  We demonstrate the detection of cyclotron resonance in graphene by using a
photo-induced thermionic emission mechanism at the graphene/MoS2 van der Waals
(vdW) Schottky junction. At cyclotron resonance in Landau-quantized graphene,
the infrared light is absorbed and an electron-hole pair is generated. When the
energy of a photoexcited electron exceeds the band offset energy at the
graphene/MoS2 interface, the electron transfer occurs from graphene to the
conduction band of MoS2, and the hole remains in graphene. This creates an
electron-hole separation at the graphene/MoS2 interface at cyclotron resonance
and a photovoltage is generated. The proposed method is an infrared
photodetection technique through out-of-plane transport at the vdW junction,
which is distinct from the previously reported methods that use in-plane
transport in graphene for electronic detection of the cyclotron resonance.
Despite the simple structure of our device with a single-vdW junction, our
method exhibits a very high sensitivity of about 10^6 V/W, which shows an
improvement of three orders of magnitude over the previously reported values.
Therefore, the proposed method displays a high potential for cyclotron
resonance-based infrared photodetector applications.
