Replacing metals with alternative plasmonic substances in plasmonics and metamaterials: Is it a good idea?

Metals, which dominate the fields of plasmonics and metamaterials suffer from large ohmic losses. New plasmonic materials, such as doped oxides and nitrides, have smaller material loss, and using them in place of metals carries a promise of reduced-loss plasmonic and metamaterial structures, with sharper resonances and higher field concentration. This promise is put to a rigorous analytical test in this work and it is revealed that having low material loss is not sufficient to have a reduced modal loss in plasmonic structures, unless the plasma frequency is significantly higher than the operational frequency. Using examples of nanoparticle plasmons and gap plasmons one comes to the conclusion that even in the mid-infrared spectrum metals continue to hold advantage over the alternative media. The new materials may still find application niche where the high absorption loss is beneficial, e.g. in medicine and thermal photovoltaics.