Without external influences, electrons within an atom typically reside in the ground state, characterized by the lowest possible values of the principal and orbital angular momentum quantum numbers, 1 and 0, respectively. Recent studies have shown that the introduction of gauge flux into an artificial crystal plaquette can induce topological Wannier cycles originating from $1s$-like orbitals. However, the exploration of topological Wannier cycles involving complex orbits remains an open question. In this work, we experimentally realize topological dual-Wannier cycles, driven by the insertion of gauge flux into an orbital phononic crystal. This phononic crystal comprises disk-shaped acoustic cavities connected by pairs of parallel tubes, supporting $2s$-, $3p$-, and $4d$-like orbitals. The insertion of gauge flux is achieved by introducing a step screw dislocation, which induces cyclic spectral flows that bridge higher-order topological band gaps. By combining the orbital degree of freedom, these cyclic spectral flows give rise to dual-topological boundary states localized at the dislocation core. Our findings not only deepen the understanding of artificial gauge flux but also open new avenues for exploring orbital-related phenomena in classical wave systems.

Close

PrevNext

View figure in article

• Topological defects
• Topological phases of matter
• Phononic crystals
• Acoustic techniques
• Tight-binding model