Magnetically-defined topological edge plasmons in edgeless electron gas

Understand

Topological materials bear gapped excitations in bulk yet protected gapless excitations at boundaries.

• Magnetoplasmons (MPs), as high-frequency density excitations of two-dimensional electron gas (2DEG) in a perpendicular magnetic field, embody a prototype of band topology for bosons.
• The time-reversal-breaking magnetic field opens a topological gap for bulk MPs up to the cyclotron frequency; topologically-protected edge magnetoplasmons (EMPs) bridge the bulk gap and propagate unidirectionally along system's boundaries.
• However, all the EMPs known to date adhere to physical edges where the electron density terminates abruptly.