The linewidth of bulk plasmons in a rapid-quench ${\mathrm{Al}}_6$Mn quasicrystal is found to increase by ∼40% as compared with that observed in a thermally annealed crystalline ${\mathrm{Al}}_6$Mn sample. A narrower plasmon linewidth is also observed in a sputtered amorphous ${\mathrm{Al}}_6$Mn thin-film sample. We believe that the unusual plasmon line broadening in ${\mathrm{Al}}_6$Mn quasicrystals is a result of increased interband transitions due to the icosahedral symmetry of the quasicrystal, and not a consequence of lattice disorder.

• Received 21 April 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.743