One-dimensional plasmons in ultrathin metallic silicide wires of finite width

The acoustic dispersion of plasmons (PLs) in narrow (4 nm) and ultrathin (one unit cell) metallic DySi(2) wires, grown by self-assembly on vicinal Si(100)-[011] 4 degrees turns out to be unidirectional. We observed the lowest intersubband PL as well as the acoustic PL. These PLs are specific for narrow metallic strips of finite width. Our experimental and theoretical analysis suggests that only one of two electron pockets in the surface Brillouin zone makes a substantial contribution to the PLs because the other pocket has a much smaller conductive character due to a strong admixture of electronic states with d character.