Experimental observation of topologically quantized alignment

Observe topologically quantized alignment in an experimentally accessible rapidly rotating nuclear system, including the associated quantized relation between the first Chern number on the cranking-axis orientation sphere and the orientation-averaged aligned angular momentum.

Background

Topologically quantized alignment (TQA) was proposed as a geometric description of rotational alignment in rapidly rotating nuclei, with the first Chern number associated with the sphere of cranking-axis orientations quantizing the Hilbert-space-averaged angular momentum aligned with the cranking axis. The paper provides a microscopic realization through exact diagonalization of a two-orbital cranking seniority Hamiltonian and identifies distinct phases, including an intermediate phase in which the Chern number is nonzero while the averaged alignment has not yet reached its quantized value.

The experimental status remains unresolved: the paper notes that TQA has not been observed experimentally. Establishing such an observation would require connecting the topological and alignment quantities to measurable spectroscopic signatures, such as spin alignment, backbending or upbending behavior, intrinsic-configuration changes, and electromagnetic or transfer matrix elements.