Quantum metric and wave packets at exceptional points in non-Hermitian systems

Topological physics is based on topological invariants such as the Chern number, which integral of Berry curvature. The quantum metric complementary to curvature in geometric tensor, but its role much less understood. authors show here that it becomes dominant for wave-packet dynamics at exceptional points strongly non-Hermitian systems. demonstrate that, thanks divergent metric, wave packets (e.g., light beams) exhibit nonvanishing velocity with controllable direction.