Experimental observation of repulsively bound magnons

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism
• Spectroscopy

Background:

• Composite objects are typically formed by attractive forces.
• Repulsively bound composite objects were thought to be fragile and theoretical.
• Previous research demonstrated repulsively bound atom pairs in optical lattices, but analogues in condensed matter were lacking due to decay channels.

Purpose of the Study:

• To experimentally identify spectroscopic signatures of repulsively bound magnon states in a condensed matter system.
• To investigate the properties and stability of these repulsively bound magnon states.
• To explore potential applications of these states in quantum information processing.

Main Methods:

• Terahertz spectroscopy measurements on the Ising-like chain antiferromagnet BaCo2V2O8.
• Comparison of experimental data with theoretical results for the Heisenberg-Ising chain model.
• Analysis of spectroscopic signatures below the quantum critical point in large transverse fields.

Main Results:

• Spectroscopic signatures of repulsively bound three-magnon states and bound magnon pairs were identified.
• These repulsively bound magnon states are energetically well-separated from continua.
• The observed states exhibit significant dynamical responses and are sufficiently long-lived despite dissipation.

Conclusions:

• Repulsively bound magnon states exist and can be experimentally identified in condensed matter systems like BaCo2V2O8.
• These states are stable and possess unique properties, suggesting potential for technological applications.
• The discovery opens avenues for utilizing magnon bound states in magnonics-based quantum information processing.