Photo-Nernst effect used to detect cyclotron resonance in graphene

Graphene has the potential to enable advanced photodetectors and other thermal technologies by combining cyclotron resonance in the presence of an external magnetic field, with infrared light absorption. Unfortunately, the photon-to-charge conversion in graphene hasn’t been efficient enough for certain applications.

Researchers have turned to the photo-thermoelectric effect to increase the photon-to-charge conversion, specifically the photo-Seebeck effect. Moriya et al. explored the much-less studied photo-Nernst effect to study cyclotron resonance in partially irradiated graphene.

Unlike the Seebeck effect, which generates a voltage parallel to the temperature gradient, the Nernst effect generates a voltage perpendicular to the same gradient. The researchers studied the latter effect using a two-terminal device consisting of a graphene monolayer, which was exposed to an external magnetic field and sandwiched between two boron nitride layers.

During the experiment, half of the graphene channel was exposed to irradiation, while the other half was covered by a palladium mask. The irradiation created a temperature gradient perpendicular to the voltage probes, and the voltage generated along the graphene channel was monitored during the experiment.

“We investigated the dependence of the photo-Nernst effect on the magnetic field and excitation wavelength, which revealed a significant enhancement of the photo-Nernst signal at the cyclotron resonance conditions in graphene,” author Rai Moriya said.

Their results showed that the Nernst effect, in addition to the Seebeck effect, can provide an alternate way to monitor the cyclotron resonance in graphene, which can be used for light detection. The researchers hope the new approach can lead to better light detectors, perhaps for detecting high-frequency light waves up to the terahertz range as well.

Source: “Photo-Nernst detection of cyclotron resonance in partially irradiated graphene,” by Rai Moriya, Kei Kinoshita, Satoru Masubuchi, Kenji Watanabe, Takashi Taniguchi, and Tomoki Machida, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5119722 .