Dirac mass induced by optical gain and loss

Area of Science:

• Condensed Matter Physics
• Quantum Optics
• Photonics

Background:

• Particle mass traditionally viewed as intrinsic, but modern physics shows complex origins like the Higgs mechanism.
• In crystal lattices, Dirac particles gain mass from symmetry-breaking perturbations, assuming energy conservation (Hermiticity).

Purpose of the Study:

• To experimentally demonstrate mass generation in Dirac quasiparticles via non-Hermitian perturbations (optical gain/loss).
• To investigate the effects of spacetime engineering of gain/loss-induced Dirac mass on quasiparticle behavior.

Main Methods:

• Utilized a photonic synthetic lattice to create and manipulate Dirac quasiparticles.
• Introduced non-Hermitian perturbations (optical gain and loss) to induce Dirac mass.
• Engineered the spacetime distribution of gain and loss.

Main Results:

• Successfully generated Dirac mass using non-Hermitian optical gain and loss.
• Observed Klein tunnelling at spatial boundaries.
• Discovered a novel flux non-conservation effect at domain walls due to local non-Hermitian symmetry breaking.
• Observed a variant of time-reflection at temporal boundaries, with velocity reversal in the non-relativistic limit and velocity retention in the relativistic limit.

Conclusions:

• Non-Hermitian perturbations offer a new route to generating Dirac mass, distinct from conventional Hermitian mechanisms.
• Spacetime engineering of gain and loss in photonic lattices enables control over quasiparticle dynamics, revealing new quantum phenomena.