A single electron as a real charge density in a 2D harmonic well. A winding state
ψ=R(r)eimφ is a real charge vortex: the density circulates as a
genuine current j=ρv, carrying angular momentum Lz=m and magnetic moment
μz=−mμB. No complex plane is needed for the flow โ only the integer m,
fixed by single-valuedness (∮v·dℓ=2πm). The field slider drives the exact
Fock–Darwin response: linear Zeeman splitting plus the quadratic diamagnetic shift.
Colour = charge density ρ=|ψ|². Dots = charge advected by the current
v=(m/r)φ̂. For m≠0 the density is hollow on the axis (the vortex core).
Lz (angular momentum)0
μz / μB0
circulation ∮v·dℓ / 2π0
〈r²〉 (mean-square size)1.000
χdia = −¼〈r²〉−0.250
energy E(m)1.000
— Zeeman (−mμBB)0.000
— diamagnetic (∝B²)0.000
split |E(+|m|)−E(−|m|)|0.000
Atomic units: ℏ=me=e=1, well ω=1, so μB=½ and
ωc=B. Levels E=(2nr+|m|+1)Ω−½mB, Ω=√(1+(B/2)²)
(Fock–Darwin), with 〈r²〉=(2nr+|m|+1)/Ω. χdia=−¼〈r²〉
is the 2D Langevin susceptibility — the same 〈r²〉-law as the atomic
χ=−(NAe²/6mec²)〈r²〉.
Fock–Darwin fan: E(m) vs B for m=−2…+2 at the selected nr. The lines
split linearly (Zeeman) and bend upward together (diamagnetism). Marker = current B.