Topological Insulator — Edge-State Protection Lab

Sample regime

Boundary channel is symmetry-protected — it ignores every defect it crosses.

Disorder

Defect density 14%

Click any lattice site to toggle a single defect by hand.

Carrier speed

Hop rate 1.0×

Live readout

Bulk backscatters

Bulk confinement R

0.0

Edge laps completed

Edge backscatters

How it works

Every dot is a lattice site; red dots are impurities that scatter an electron off its path. The orange carrier hops randomly through the bulk and bounces backward whenever it lands on a defect — with enough disorder it never wanders far from where it started, an everyday picture of Anderson localization.

The cyan carrier instead rides a one-way channel bound to the sample's boundary. In a topological sample that channel is protected by the bulk band topology: back-scattering would require flipping to a partner state that simply doesn't exist at that energy, so the carrier glides through every defect it meets. Flip the toggle to trivial and that protected channel disappears — the same carrier now scatters and localizes exactly like the bulk one.

Defect density — fraction of sites that scatter carriers; raise it and watch the bulk trajectory shrink.
Click a site — hand-place or remove a single impurity anywhere, including right on the boundary path.
Regime toggle — switches whether the boundary channel is topologically protected or an ordinary, scatterable edge.

Lattice site Defect Bulk carrier Edge carrier

click a site to toggle a defect

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