Observation of Floquet tensor monopoles

Tensor monopoles, topological singularities of Kalb–Ramond tensor gauge fields, have garnered widespread attention in high-energy and condensed matter physics. They give rise to exotic phenomena such as quantized magnetoelectric responses and chiral boundary states, acting as potential building blocks for the development of topological devices in high-dimensional space. However, theoretical studies and experimental realizations reported to date have remained in static settings, and the realization of Floquet tensor monopoles (FTMs) and their associated anomalous non-equilibrium topological features has yet to be achieved. Here, we report the first theoretical and experimental implementation of FTMs in a four-dimensional non-equilibrium system. We systematically uncover the driving-frequency controlled creation, motion, and annihilation of FTMs, together with their anomalous bulk-edge correspondence. These phenomena are unique to FTMs and have no static counterparts. In experiments, we design and fabricate time-varying topological circuits, and directly observe the controllable motion of FTMs in k-space and their induced 3D Fermi-arc surface states by tuning the driving frequency. Our findings extend tensor monopole research to the non-equilibrium regime, providing a theoretical and experimental platform for exploring exotic topological phases in dynamic tensor gauge fields and laying the groundwork for functional topological devices with real-time control.