Surfacelocalized

Surfacelocalized, often written surface-localized, is a term used to describe states or excitations whose amplitude is concentrated near a material surface or interface and decays into the adjoining medium. In this sense, a surfacelocalized mode is distinct from bulk states that extend throughout the interior of a material. The localization is typically characterized by a decay length, with the wavefunction or field magnitude falling off away from the surface, often approximately as exp(-z/ξ) for distance z from the surface.

In condensed matter physics, surfacelocalized states arise at crystal terminations, interfaces, or defects. Classic examples include Shockley and Tamm surface states in solids and, in topological materials, surface states that span the bulk band gap with spin textures dictated by spin-orbit coupling. The presence and energy of these states depend on surface termination, reconstruction, and environmental conditions, and they can play a key role in electronic transport and catalysis at surfaces.

In photonics and plasmonics, surfacelocalized modes include surface plasmon polaritons at metal-dielectric interfaces and other evanescent modes confined near interfaces. These modes enable subwavelength light confinement and are central to sensing and nanoscale optics.

In chemistry and materials science, surfacelocalized orbitals or excitations refer to electronic states localized on surface atoms, which influence adsorption, catalysis, and surface reactivity.

Methods to study surfacelocalized phenomena include scanning tunneling microscopy and spectroscopy, angle-resolved photoemission spectroscopy, and theoretical approaches such as tight-binding models and first-principles calculations that impose appropriate boundary conditions to capture surface localization.