Composite-fermion geometric resonance ($R_c^{\ast }=\hslash \sqrt{4\pi n_s}/(e|B-2h{n}_s/e|)$)

A fully spin-polarized sea of composite fermions has a Fermi wavevector $\sqrt{4\pi n_s}$. Near half filling its semiclassical orbit radius depends on the residual effective field, not the full applied field. Matching an orbit diameter to a patterned length can produce transport resonances outside an incompressible fractional Hall state. Multiple pattern periods and random/unpatterned controls test that geometric interpretation. Density inhomogeneity and a soft potential can shift or broaden the response.^[ref]