Utilizing Fermi arc states in photonic crystals for ultrasensitive gas detection

We demonstrate a gas detector based on sensitive Tamm plasmon polaritons (TPPs) at the interface between a 1D photonic crystal (PC) and a monolayer graphene sheet. To obtain those states and control their properties for a chosen wavelength, we map Fermi arc states existing in a synthetic geometrical space into real-space interface TPP states, which enables us to design a structure allowing detection of an ultralow concentration of NO₂, i.e., below 1 ppb. We also present that a simple addition of a defect layer may deliver a mechanism for a quantitative measurement of gas concentration. We demonstrate that our device, despite its simple design and single-surface gas exposure, overcomes sensitivity limitations of a standalone graphene monolayer to a level unprecedented in similar graphene-based sensor setups.