Quantum metric and wavepackets at exceptional points in non-Hermitian systems

TL;DR

This paper reveals that the quantum metric becomes a key factor in non-Hermitian systems near exceptional points, dictating wavepacket dynamics and diverging behavior, which differs from traditional topological concepts.

Contribution

It introduces the quantum metric as a crucial quantity near exceptional points, showing its divergence and impact on wavepacket trajectories in non-Hermitian systems.

Findings

Quantum metric diverges at exceptional points.

Wavepackets experience constant acceleration and velocity.

Results are independent of wavepacket size.

Abstract

The usual concepts of topological physics, such as the Berry curvature, cannot be applied directly to non-Hermitian systems. We show that another object, the quantum metric, which often plays a secondary role in Hermitian systems, becomes a crucial quantity near exceptional points in non-Hermitian systems, where it diverges in a way that fully controls the description of wavepacket trajectories. The quantum metric behaviour is responsible for a constant acceleration with a fixed direction, and for a non-vanishing constant velocity with a controllable direction. Both contributions are independent of the wavepacket size.