Observation of Higher-order Topological Bound States in the Continuum using Ultracold Atoms

TL;DR

This paper reports the experimental realization of higher-order topological bound states in the continuum using ultracold atoms to simulate a 2D topological model, revealing new quantum phenomena and phase transitions.

Contribution

The study introduces a programmable ultracold atom platform to simulate higher-order topological states and observe their dynamics and phase transitions in synthetic dimensions.

Findings

Observation of corner and edge-bound states in a 2D topological lattice

Demonstration of adiabatic preparation of higher-order topological states

Measurement of topological phase transition via bulk invariant

Abstract

Simulating higher-order topological materials in synthetic quantum matter is an active research frontier for its theoretical significance in fundamental physics and promising applications in quantum technologies. Here we experimentally implement two-dimensional (2D) momentum lattices with highly programmable ability using ultracold 87Rb atoms. Through precise control of experimental parameters, we simulate a 2D Su-Schrieffer-Heeger model with this technique, and observe the characteristic dynamics of corner and edge-bound states, where the corner state is identified as a higher-order topological bound state in the continuum. We further study the adiabatic preparation of the corner state by engineering evolutions with time-dependent Hamiltonians. We also demonstrate the higher-order topological phase transition by measuring both the bulk topological invariant and the topological corner state. Our new platform opens the avenue for exploring the exotic dynamics and topology in higher synthetic dimensions, making use of the rich degrees of freedom of cold atoms systems.