Dynamical Solitons and Boson Fractionalization in Cold-Atom Topological Insulators.

Area of Science:

• Condensed Matter Physics
• Quantum Many-Body Systems
• Ultracold Atomic Gases

Background:

• The Z_{2} Bose-Hubbard model describes interacting bosons with a dynamical Z_{2} field.
• Spontaneous symmetry breaking (SSB) and topological symmetry protection are key concepts in understanding exotic quantum phenomena.

Purpose of the Study:

• To investigate fractional topological phenomena in the Z_{2} Bose-Hubbard model at incommensurate fillings.
• To demonstrate the emergence and properties of topological defects in the ground state.

Main Methods:

• Analysis of the Z_{2} Bose-Hubbard model with interacting bosons and a dynamical Z_{2} field.
• Investigation of spontaneous symmetry breaking (SSB) and topological symmetry protection.
• Application of a pumping argument to confirm the survival of phenomena with finite interactions.

Main Results:

• Topological defects appear in the ground state, linking different SSB sectors.
• These dynamical defects carry topological charge and fractional particle numbers.
• Boson fractionalization induced by topological defects is shown to occur in strongly correlated systems.

Conclusions:

• The study reveals novel fractional topological phenomena in ultracold atomic systems.
• Topological defects provide a mechanism for boson fractionalization.
• These findings bridge concepts from solid-state and high-energy physics with ultracold atom experiments.