  We explore the potential of highly mismatched alloys (HMAs) for realizing
lossless plasmonics. Systems with a plasmon frequency at which there are no
interband or intraband processes possible are called lossless, as there is no
2-particle loss channel for the plasmon. We find that the band splitting in
HMAs with a conduction band anticrossing guarantees a lossless frequency
window. When such a material is doped, producing plasmonic behavior, we study
the conditions required for the plasmon frequency to fall in the lossless
window, realizing lossless plasmons. Considering a generic class of HMAs with a
conduction band anticrossing, we find universal contours in their parameter
space within which lossless plasmons are possible for some doping range. Our
analysis shows that HMAs with heavier effective masses are most promising for
realizing a lossless plasmonic material.
