can FDTD modify the results with quantum theory when the size of metal structure is about 1nm ?



There is always the nanogap smaller than 1 nm in the dimmer, trimmer and some other metal nanostructures .
The quantum effect or nonlocal effect will significantly affect the optical properties of these structures. Even, a 150 nm shift in the surface plasmon resonance occur.
The FDTD is known as a classical EM theory, so the question is: can we modify the FDTD code to meet the quantum or nonlocal effect.


Hi @wanghl0811,

FDTD is a method to solve the macroscopic Maxwell equations for classical electromagnetic fields. Furthermore, we assume that the response of materials can be described by a frequency-dependent local permittivity. Any effects that cannot be captured with this type of model lie beyond what we can simulate with FDTD Solutions.

As you mentioned, the correct simulation of the coupling between metal nanostructures across very small gaps, in the subnanometer regime, require including quantum effects. However, there are some tricks to model these quantum effects using a local dielectric response; for example, the “quantum-corrected model” described in this article: Such model could be potentially used in FDTD.


there is a simple treatment on the tranditional model in this article

could you provide some corrected models like nano dimmer and nanoparticle on film with FDTD to simulate the nonlocal effect in the small gaps?


Hi @wanghl0811,

We don’t have a ready-made model for this specific purpose, but you can use our tools to implement the simple model described in the reference you mentioned above. If I understood correctly you simply need to use a metal and a dielectric described by local frequency-dependent permitivity models. We provide a wide variety of models of this type that you can use. A good starting point would be reproducing the results in the paper with a simple geometry (maybe the gap between two metal layers).


Ideally, the corrected FDTD calculations will be accurate if you know the conductivity of the ‘fictitious’ medium. The conductivity can be considered by taking into account the physical process that leads to non-locality or quantum effects (such as electron tunnelling through the materials or air).