Experimental Measurement of the Berry Curvature from Anomalous Transport

TL;DR

This paper demonstrates the first experimental method to directly measure Berry curvature using wave packet dynamics in an optical system, revealing its influence on anomalous displacement in a 1D charge pump.

Contribution

It introduces a novel experimental approach to map Berry curvature through wave packet dynamics in optical fibers, bridging geometrical band properties with observable effects.

Findings

First direct measurement of Berry curvature in an optical system

Wave packet dynamics reveal anomalous displacement due to Berry curvature

Method provides high-resolution mapping of geometrical properties

Abstract

Geometrical properties of energy bands underlie fascinating phenomena in a wide-range of systems, including solid-state materials, ultracold gases and photonics. Most famously, local geometrical characteristics like the Berry curvature can be related to global topological invariants such as those classifying quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a wave packet. Here, we experimentally demonstrate for the first time that wave packet dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time-evolution of a wave packet in a 1D geometrical "charge" pump, where the Berry curvature leads to an anomalous displacement of the wave packet under pumping. This is both the first direct observation of Berry curvature effects in an optical system, and, more generally, the proof-of-principle demonstration that semi-classical dynamics can serve as a high-resolution tool for mapping out geometrical properties.