Can the Plasmon Frequency in Metals Be Changed Experimentally?

[ahatef]

Hi guys;

I have a question about the Plasmon frequencies in metals I know that it can be calculated as following:
ωp²=Ne²/ε₀m_eff
I was just wondering if anyone knows it is possible to change the plasmon frequency of any metal let say silver experimentally or not. I am working on metallic photonic crystals I want to find the effect of plasmon frequency on photonic band gap.
Thanks

 

[nbo10]

Change either the electron density or the electrons effective mass.