# Wolfram Language™

## Find Aharonov–Bohm Eigenvalues

The AharonovBohm effect is a quantum mechanical phenomenon where a charged particle detects an electromagnetic gauge potential even though the magnetic field inside the region where the particle can move is zero. In this example, the Schrödinger equation for a fixed magnetic field concentrated at a line perpendicular to the domain of the particle is considered.

Specify the region as sector in the plane centered about the axis.

In:= `\[CapitalOmega] = Disk[{0, 0}, 1, {-\[Pi]/8, \[Pi]/8}];`

Specify the AharonovBohm operator. The magnetic field is restricted to the axis.

In:= ``` A = 1/2 {-(y - b), x - a}/((x - a)^2 + (y - b)^2) /. {a -> 0.2, b -> 0.4}; \[ScriptCapitalL] = -Laplacian[u[x, y], {x, y}] + I Div[A, {x, y}] u[x, y] + 2 I A.D[u[x, y], {{x, y}}] + A.A u[x, y];```

Specify Dirichlet boundary conditions on the entire boundary.

In:= `\[ScriptCapitalB] = DirichletCondition[u[x, y] == 0, True];`

Compute six eigenvalues and eigenfunctions of the operator.

In:= ```{vals, funs} = NDEigensystem[{\[ScriptCapitalL], \[ScriptCapitalB]}, u[x, y], {x, y} \[Element] \[CapitalOmega], 6]; ```

Inspect the eigenvalues.

In:= `vals`
Out= Visualize the real part of the eigenfunctions.

show complete Wolfram Language input
In:= ```Grid[Partition[ Plot3D[Re[#], {x, y} \[Element] \[CapitalOmega], ColorFunction -> "TemperatureMap", Boxed -> False, Axes -> None, PlotRange -> All, PlotStyle -> {Specularity[White, 20]}, Method -> {"ShrinkWrap" -> True}] & /@ funs, 3], Background -> Transparent] // Quiet```
Out= 