engleski

Low-energy plasmons in quantum-well and surface states of metallic thin films

We studied the low-energy plasmons in ultrathin films of silver in the thicknesses regime where the surface states as well as quantum-well states must play significant roles. Realistic band structure was adopted for assessing the quantum-mechanical effect on the low-energy charge dynamics. Besides the expected quasi two-dimensional plasmon mode, we find the modes which resemble an acoustic surface plasmon on semi-infinite metal surfaces and an additional plasmon mode related to the inter-band transitions between the two slab-split surface states. It is found that the dispersion of the latter mode is almost identical to the acoustic surface plasmon except the energy offset at small momenta values. The peaks in the surface response function related to inter-band transitions between the surface-like states and bulk-like states are identified as well. The present work elucidates the role of quantized electronic states and surface states on the plasmonic excitations in the ultimately thin films potentially used in the future nano optics devices.

acoustic surface plasmon ; quantum size effect

nije evidentirano