  Vortices are topological defects of type-II superconductors in an external
magnetic field. In a similar fashion to a quantum anomalous Hall insulator,
quantum anomalous vortex (QAV) spontaneously nucleates due to orbital-and-spin
exchange interaction between vortex core states and magnetic impurity moment,
breaking time-reversal symmetry (TRS) of the vortex without an external field.
Here, we used scanning superconducting quantum interference device microscopy
(sSQUID) to search for its signatures in iron-chalcogenide superconductor
Fe(Se,Te). Under zero magnetic field, we found a stochastic distribution of
isolated anomalous vortices and antivortices with flux quanta $\Phi_0$. By
applying a small local magnetic field under the coil of the nano-SQUID device,
we observed hysteretic flipping of the vortices reminiscent of the switching of
ferromagnetic domains, suggesting locally broken-TRS. We further showed
vectorial rotation of a flux line linking a paired vortex-antivortex with the
local field. These unique properties of the anomalous vortices satisfied the
defining criteria of QAV. Our observation suggests a quantum vortex phase with
spontaneous broken-TRS in a high-temperature superconductor.
