Snell's law for surface electrons: Refraction of an electron gas imaged in real space

TL;DR

This paper demonstrates that surface electron waves on NaCl/Cu(111) follow Snell's law of refraction, with real-space imaging revealing wave behavior at interfaces and step edges.

Contribution

It provides direct real-space imaging evidence that surface electron waves obey Snell's law, linking quantum wave behavior with classical optics.

Findings

Surface electron waves exhibit refraction at NaCl island edges.

Standing wave patterns are observed and analyzed.

Wave behavior conforms to Snell's law in a surface electron context.

Abstract

On NaCl(100)/Cu(111) an interface state band is observed that descends from the surface-state band of the clean copper surface. This band exhibits a Moire-pattern-induced one-dimensional band gap, which is accompanied by strong standing-wave patterns, as revealed in low-temperature scanning tunneling microscopy images. At NaCl island step edges, one can directly see the refraction of these standing waves, which obey Snell's refraction law.