Spectral Crossings Diagnose Multiply Quantized Vortex Splitting

Abstract

A charge-$r$ coupling vortex can remain as one fused order-$r$ zero or split into $r$ nearby unit-charge zeros after weak symmetry breaking. The two configurations have the same total winding and the same number of dark states in the lowest-Landau-level projection, so neither the imposed orbital angular momentum nor the total winding number distinguishes their local geometry. We study this distinction in a two-component Haldane-sphere model coupled by a Raman field. For monopole flux $N$, the detuning ${\tau }_{\mathrm{c}}$ at which a defect branch crosses zero energy scales as $|{\tau }_{\mathrm{c}}|\sim N^{-(r+1)}$ for a fused zero and $N^{-2}$ for resolved unit zeros. A Feshbach reduction establishes these asymptotic laws for the full multiband Hamiltonian, and numerical calculations in a monopole-harmonic basis confirm the fused-vortex scaling for $r=1,2,3$. For a partially split cluster of diameter $d$, the scaling crosses over when $d$ is comparable to the magnetic length ${\ell }_B$, allowing $d$ to be inferred spectroscopically even below the spatial resolution of direct imaging.

arXiv comment5 pages, 3 figures; Supplemental Material included