Surface plasmon: Difference between revisions - Wikipedia

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[[File:Sketch of surface plasmon.png| thumb|350px |Schematic representation of an electron density wave propagating along a metal–[[Dielectrics|dielectric]] interface. The charge density oscillations and associated electromagnetic fields are called [[Surface plasmon polariton|surface plasmon-polariton]] waves. The exponential dependence of the electromagnetic field intensity on the distance away from the interface is shown on the right. These waves can be excited very efficiently with light in the visible range of the electromagnetic spectrum.]]

'''Surface plasmons''' ('''SPs''') are coherent [[delocalized electron]] oscillations that exist at the interface between any two materials where the real part of the [[Permittivity#Complex permittivityDielectric|dielectric function]] changes sign across the interface (e.g. a metal-dielectric interface, such as a metal sheet in air). SPs have lower energy than bulk (or volume) [[plasmon]]s which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an [[Fermi gas|electron gas]] (or plasma).

The charge motion in a surface plasmon always creates electromagnetic fields outside (as well as inside) the metal. The ''total'' excitation, including both the charge motion and associated electromagnetic field, is called either a [[surface plasmon polariton]] at a planar interface, or a [[localized surface plasmon]] for the closed surface of a small particle.