  Quantum Hall effect (QHE) is one of the most fruitful research topics in
condensed-matter physics. Ordinarily, the QHE manifests in a ground state with
time-reversal symmetry broken by magnetization to carry a quantized chiral edge
conductivity around a two-dimensional insulating bulk. We propose a theoretical
concept and model of non-equilibrium excited-state QHE (EQHE) without intrinsic
magnetization. It arises from circularly polarized photoexcitation between two
enantiomorphic flat bands of opposite chirality, each supporting originally a
helical topological insulating state hosted in a Yin-Yang Kagome lattice. The
chirality of its edge state can be reversed by the handedness of light, instead
of the direction of magnetization as in the conventional quantum (anomalous)
Hall effect, offering a simple switching mechanism for quantum devices.
Implications and realization of EQHE in real materials are discussed.
