Feshbach Resonance 2D: Tuning Atomic Interactions

A magnetic Feshbach resonance is the tool that turns an ultracold atomic gas into a fully tunable quantum system: sweeping an external magnetic field near the resonance pole drives the s-wave scattering length through zero and out to ±∞, switching the atoms between weak background interactions, a strongly interacting unitary regime, and a gas of shallow diatomic molecules. This 2D simulator renders a top-down box of atoms alongside a live a(B) curve plot, computing the real Feshbach formula a(B) = a_bg(1 − Δ/(B−B0)) directly from your field, width and background-length sliders, and driving the atoms' capture radius and binding behaviour from that scattering length — cross the resonance and watch free atoms pair into gold, tethered molecules exactly where the physics says a shallow bound state should appear.