Simulations based on surface conductivity and volumetric permittivity of graphene produce a huge difference on resonance wavelength of graphene nanostripe

I had simulated a graphene nanostripe based on surface conductivity mode and volumetric permittivity mode of graphene, respectively. Results showed that resonance wavelength of graphene nanostripe obtained by surface conductivity was about 1500nm larger than that obtained by volumetric permittivity of graphene. Why there are so big difference?
My simulation file:surface conductivity mode of graphene.fsp (252.4 KB) and volumetric permittivity mode of graphene.fsp (250.2 KB)
The transmission spectra are as follows:

Thanks for any help.

I haven’t looked in great detail at your simulation, but I didn’t see anything immediately wrong with the setup. My guess is that the volumetric permittivity is calculated using a formula which is valid in the mid-IR wavelength range, whereas you are simulating a wavelength outside of the range. I would guess that the result of the surface conductivity model is more accurate since you are operating outside of the mid-IR range.

Thank you for your reply. I removed the substrate and changed the wavelength range, but the difference between the two approaches still large.The transmission spectra are as follows:

The materials parameters are as follows:
Ef = 0.4 eV, Γ=ћ/2τ, the length and width of the graphene nanostripe are 100 nm and 50 nm, respectively.
Looking forward to your reply.


The mid-IR range where the volumetric permittivity model is valid is between 3 to 5 microns. It looks like you are still operating outside of this range (from 6 to 11.8 microns). In this case, I would suggest using the graphene material model with 2D rectangle since it will be valid over a broader wavelength range.