CMT139

Surface States, Edge Currents and the Angular Momentum of Chiral p-wave Superfluids

• Author(s): J. A. Sauls
• Address: Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208
• Date: September 25, 2011
• Journal: Phys. Rev. B 84, 214509 (2011) [DOI]
• Abstract: The spectra of fermionic excitations, pairing correlations and edge currents confined near the boundary of a chiral p-wave superfluid are calculated to leading order in ℏ/p_f ξ. Results for the energy- and momentum-resolved spectral functions, including the spectral current density, of a chiral p-wave superfluid near a confining boundary are reported. The spectral functions reveal the subtle role of the chiral edge states in relation to the edge current and the angular momentum of a chiral p-wave superfluid, including the rapid suppression of L_z(T) for 0 ≲ T ≪ T_c in the fully gapped 2D chiral superfluid. The edge current and ground-state angular momentum are shown to be sensitive to boundary conditions, and as a consequence the topology and geometry of the confining boundaries. For perfect specular boundaries the edge current accounts for the ground-state angular momentum, L_z=(N/2) ℏ, of a cylindrical disk of chiral superfluid with N/2 fermion pairs. Non-specular scattering can dramatically suppress the edge current. In the limit of perfect retro-reflection the edge states form a flat band of zero modes that are non-chiral and generate no edge current. For a chiral superfluid film confined in a cylindrical toroidal geometry the ground-state angular momentum is, in general, non-extensive, and can have a value ranging from L_z>(N/2) ℏ to L_z < -(N/2) ℏ depending on the ratio of the inner and outer radii and the degree of back scattering on the inner and outer surfaces. Non-extensive scaling of L_z, and the reversal of the ground-state angular momentum for a toroidal geometry, would provide a signature of broken time-reversal symmetry of the ground state of superfluid ³He-A, as well as direct observation of chiral edge currents.

• Comment: 11 pages, 9 figures, with a historical review of the angular momentum paradox in ³He-A

• Eprint: [arXiv] [PDF]

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