Emergent Fine Structure Constant of Quantum Spin Ice Is Large

Area of Science:

• Condensed-matter physics
• Quantum field theory
• Magnetism

Background:

• Condensed-matter systems can host emergent phenomena distinct from the standard model.
• Quantum spin ice is a topological magnet exhibiting fractionalized magnetic monopoles.
• Emergent quantum electrodynamics (QED) in quantum spin ice differs from standard QED.

Purpose of the Study:

• To investigate the fine-structure constant (α) in emergent QED within quantum spin ice.
• To explore the tunability of emergent QED parameters in quantum spin ice.
• To assess quantum spin ice as a platform for quantum simulation and studying exotic quantum field theories.

Main Methods:

• Theoretical analysis of emergent QED in quantum spin ice.
• Investigating the role of the microscopic Hamiltonian in tuning emergent parameters.
• Comparing emergent QED parameters with those of standard QED.

Main Results:

• The fine-structure constant in quantum spin ice (α_QSI) is over an order of magnitude larger than in standard QED (α_QED ≈ 1/137).
• α_QSI, the emergent speed of light, and other QED parameters are tunable via the microscopic Hamiltonian.
• α_QSI can be tuned from zero to the strong-coupling limit where QED confines.

Conclusions:

• Quantum spin ice provides an ideal platform for studying exotic quantum field theories due to its tunable, strong-coupling emergent QED.
• Its constrained Hilbert space makes it suitable for quantum simulation.
• Experiments on quantum spin ice should focus on phenomena arising from strong interactions.