Majorana Quasiparticles Protected by Z_{2} Angular Momentum Conservation

Area of Science:

• Condensed Matter Physics
• Quantum Simulation
• Cold Atom Gases

Background:

• Topological phases of matter host exotic quasiparticles like Majorana fermions.
• Symmetry protection is crucial for the stability of topological phases.
• Cold atom gases provide a controllable platform for simulating complex quantum phenomena.

Purpose of the Study:

• To investigate a novel symmetry-protected topological phase in one-dimensional (1D) cold atom gases.
• To demonstrate the stabilization of Majorana quasiparticles as edge modes.
• To explore the role of angular momentum conservation in protecting topological phases.

Main Methods:

• Investigation of a number-conserving four-species Hubbard model.
• Inclusion of spin-orbit coupling to reduce global spin symmetry.
• Application of field theory techniques to elucidate Majorana edge mode emergence.
• Corroboration using density-matrix-renormalization-group (DMRG) simulations.

Main Results:

• Angular momentum conservation was shown to stabilize a quasitopological phase.
• This phase supports Majorana quasiparticles as robust edge modes.
• Spin-orbit coupling was found to reduce spin symmetry to angular momentum parity symmetry, providing robust protection.
• The emergence of Majorana edge modes was confirmed by theoretical and numerical methods.

Conclusions:

• The study establishes a robust mechanism for stabilizing topological phases and Majorana edge modes in 1D cold atom systems.
• The findings pave the way for experimental observation of Majorana edge modes using alkaline-earth-like fermions in optical lattices.
• The demonstrated recipe utilizes experimentally realized ingredients like spin-orbit coupling and strong interorbital interactions.