Orbital angular momentum and spectral flow in two-dimensional chiral superfluids

Area of Science:

• Condensed Matter Physics
• Quantum Fluids
• Superfluidity

Background:

• Two-dimensional chiral superfluids exhibit unique quantum properties.
• Orbital angular momentum (OAM) is a key characteristic of superfluids.
• Understanding OAM in different superfluid regimes is crucial for theoretical advancements.

Purpose of the Study:

• To investigate the orbital angular momentum (OAM) in two-dimensional chiral (p_{x}+ip_{y})^{ν}-wave superfluids.
• To analyze the OAM in both Bose-Einstein condensation and BCS limits.
• To elucidate the role of spectral asymmetry and spectral flow in determining OAM.

Main Methods:

• Utilizing spectral asymmetry and spectral flow calculations.
• Analyzing N fermions on a disk at zero temperature.
• Comparing p+ip-wave superfluids with higher-order chiral superfluids (ν≥2).

Main Results:

• In the Bose-Einstein condensation regime, OAM (L_{z}) is found to be νN/2 for any integer ν.
• In the BCS limit, p+ip-wave superfluids have OAM L_{z}=N/2.
• For chiral superfluids with ν≥2 in the BCS limit, OAM is suppressed to L_{z}=N×O(Δ_{0}/ϵ_{F})≪N.

Conclusions:

• The behavior of OAM in chiral superfluids differs significantly between the BEC and BCS regimes.
• Edge mode properties and depairing effects are responsible for the suppressed OAM in higher-order chiral superfluids within the BCS limit.
• This study highlights the nuanced dependence of superfluid properties on microscopic details and theoretical frameworks.