Exceptional Nexus in Bose-Einstein Condensates with Collective Dissipation

Area of Science:

• Quantum physics
• Atomic physics
• Non-Hermitian systems

Background:

• Multistate non-Hermitian systems exhibit phenomena beyond two-level systems, such as higher-order exceptional points (EPs).
• An exceptional nexus (EX) is a third-order EP and a singularity of exceptional arcs (EAs), possessing hybrid topological characteristics.

Purpose of the Study:

• To experimentally realize an exceptional nexus (EX) in a dissipative three-state system.
• To investigate the formation and properties of EXs in a parameter space without relying on symmetry.

Main Methods:

• Implementation of a dissipative three-state system using atomic Bose-Einstein condensates.
• Engineering density-dependent dissipation through collective atomic response to resonant light.
• Analysis of system decay dynamics to observe the formation of EXs.

Main Results:

• Experimental realization of an EX in a two-parameter space without symmetry.
• Demonstration of EX formation from the coalescence of two exceptional arcs (EAs) with different geometries.
• Observation of dissipation's varied roles in the strong coupling and quantum Zeno regimes.

Conclusions:

• The study successfully demonstrates the creation of an exceptional nexus (EX) in a controllable atomic system.
• This work provides a platform for exploring higher-order exceptional physics in many-body ultracold atom systems.
• The findings highlight the potential of engineered dissipation in realizing complex topological phenomena.