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Abstract

We discuss the orbital angular momentum (OAM) and the edge-mass current in neutral fermionic superfluids with broken time-reversal symmetry. Recent mean field studies imply that total OAM of a uniform superfluid depends on boundary conditions and is not a thermodynamic quantity. We point out that this does not conflict with thermodynamics because there is no intensive external field conjugate to OAM with which a uniform superfluid is stable in the thermodynamic limit, in sharp contrast to the orbital magnetization in a nonsuperfluid system. We establish a simple physical picture for the sensitivity of OAM to boundaries by introducing the notion of "unpaired fermions" and "fermionic Landau criterion" within a mean field description. In order to go beyond the mean field approximation, we perform a density matrix renormalization group calculation and conclude that the mean field understanding is essentially correct.