Spin-Symmetry Breaking Through Metasurface Geometric Phases

Over the past decades, geometric phases have brought profound insights in both quantum and classical physics. Although metasurfaces based on the Pancharatnam-Berry phase have made great achievements in polarization optics, chiral holograms, and even quantum entanglement, the construction of other types of geometric phases remains unclear. We propose to mimic a single ballistic Aharonov-Bohm ring using meta-atoms in both spin direction and polarization state changes during spin-material interactions, resulting in an analog of the Aharonov-Anandan phase of fermion particles. By combining the Aharonov-Anandan and Pancharatnam-Berry phases, the symmetric restriction of the geometric phase is finally broken. In this way, desired phase profiles can be easily imposed on arbitrary polarization states without restricting the orthogonal limitations. The proposed geometric phases allow flexible manipulations of the photonic spin-Hall effect and enable the superposition of arbitrary spin(1/2) charges, thus breaking the conjugate constraints of the output orbital angular momentum modes. The results of this work expand the categories of geometric phases in metasurfaces and may find applications in polarization control and spin-enabled optics.