Andreev bound states at boundaries of polarized 2D Fermi superfluids with s-wave pairing and spin-orbit coupling

Abstract

A topological superfluid phase characterized by an emergent chiral-p-wave pair potential is expected to form in a two-dimensional Fermi superfluid subject to s-wave pairing, spin-orbit coupling and a large-enough Zeeman splitting. Andreev bound states appear at phase boundaries, including Majorana zero modes whose existence is assured by the bulk-boundary correspondence principle. Here we study the physical properties of these subgap-energy bound states at step-like interfaces using the spin-resolved Bogoliubov-deGennes mean-field formalism and assuming small spin-orbit coupling. Extending a recently developed spin-projection technique based on Feshbach partitioning [SciPost Phys. 5, 016 (2018)] combined with the Andreev approximation allows us to obtain remarkably simple analytical expressions for the bound-state energies as well as the majority and minority spin components of their wave functions. Besides the vacuum boundary, where a majority-spin Majorana excitation is encountered, we also consider the boundary between the topological and a nontopological superfluid phase that can appear in a coexistence scenario due to the first-order topological phase transition predicted for this system. At this superfluid-superfluid interface, we find a localized chiral Majorana mode hosted by the minority-spin sector. Our theory further predicts majority-spin subgap-energy bound states similar to those found at a Josephson junction between same-chirality p-wave superfluids. Their presence affects the Majorana mode due to a coupling of minority and majority spin sectors only in the small energy range where their spectra overlap. Our results may inform experimental efforts aimed at realizing and characterizing unconventional Majorana quasiparticles.

arXiv comment40 pages, 5 figures. Submission to SciPost. v2: minor revisions to improve presentation of the abstract and extend discussion in the conclusions section

References in corpus (62)

• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Paired states of fermions in two dimensions with breaking of parity and time-reversal symmetries, and the fractional quantum Hall effect
• New directions in the pursuit of Majorana fermions in solid state systems
• New Perspectives for Rashba Spin-Orbit Coupling
• A generic new platform for topological quantum computation using semiconductor heterostructures
• Non-abelian statistics of half-quantum vortices in p-wave superconductors
• Search for Majorana fermions in superconductors
• Topological superconductors: a review
• Majorana fermions in a tunable semiconductor device
• Majorana Zero Modes and Topological Quantum Computation
• Spin-orbit coupling in quantum gases
• Colloquium: Majorana Fermions in nuclear, particle and solid-state physics
• Non-Abelian Topological Order in S-Wave Superfluids of Ultracold Fermionic Atoms
• Condensed Matter Theory of Dipolar Quantum Gases
• Topological Phases of Noncentrosymmetric Superconductors: Edge States, Majorana Fermions, and the Non-Abelian Statistics
• From Andreev to Majorana bound states in hybrid superconductor-semiconductor nanowires
• Fermion zero modes on vortices in chiral superconductors
• Dipolar physics: A review of experiments with magnetic quantum gases
• $p_x+i{p}_y$ superfluid from s-wave interactions of fermionic cold atoms
• Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement
• Fractional ac Josephson effect in p- and d-wave superconductors
• Chiral Superconductors
• Topological Quantum Computation Based on Chiral Majorana Fermions
• Non-Abelian Topological Orders and Majorana Fermions in Spin-Singlet Superconductors
• Quasiparticle States near the Surface and the Domain Wall in a p_x\pm i p_y-Wave Superconductor
• Edge modes, edge currents, and gauge invariance in $p_x+i{p}_y$ superfluids and superconductors
• Physical mechanisms for zero-bias conductance peaks in Majorana nanowires
• Stable Topological Superfluid Phase of Ultracold Polar Fermionic Molecules
• Quantum Gases in Optical Boxes
• Two-Dimensional Homogeneous Fermi Gases
• Tomographic RF Spectroscopy of a Trapped Fermi Gas at Unitarity
• Spontaneous Hall effect in chiral p-wave superconductor
• Experimental observation of a topological band gap opening in ultracold Fermi gases with two-dimensional spin-orbit coupling
• Crossover from 2D to 3D in a weakly interacting Fermi gas
• Surface States, Edge Currents and the Angular Momentum of Chiral p-wave Superfluids
• A road to reality with topological superconductors
• Time reversal non-invariant non-Abelian topological order in non-centrosymmetric superconductors
• An Index Theorem for the Majorana Zero Modes in Chiral P-Wave Superconductors
• Andreev Bound States and Their Signatures
• Strongly interacting two-dimensional Fermi gases
• Probing Majorana fermions in spin-orbit coupled atomic Fermi gases
• Topological p_x+ip_y Superfluid Phase of Fermionic Polar Molecules
• Topological superfluid in a trapped two-dimensional polarized Fermi gas with spin-orbit coupling
• An ideal Josephson junction in an ultracold two-dimensional Fermi gas
• Role of the Majorana Fermion and the Edge Mode in Chiral Superfluidity near a p-Wave Feshbach Resonance
• Phase separation in a polarized Fermi gas with spin-orbit coupling
• Solution of the Bogoliubov-de Gennes equations at zero temperature throughout the BCS-BEC crossover: Josephson and related effects
• Conductance spectroscopy of topological superconductor wire junctions
• Single Impurity In Ultracold Fermi Superfluids
• Josephson current between chiral superconductors
• Novel $p$-wave superfluids of fermionic polar molecules
• Conductance spectroscopy of nontopological-topological superconductor junctions
• Helical spin texture of surface states in topological superconductors
• Josephson effect in two-band superconductors
• Josephson junctions of 2D time-reversal invariant superconductors: signatures of the topological phase
• Chiral twodimensional p-wave superfluid from s-wave pairing in the BEC regime
• Domain walls in chiral p-wave superconductors: Quasiparticle spectrum and dynamics
• Probing electron-hole weights of an Andreev bound state by transient currents
• Discrete symmetries of low-dimensional Dirac models: A selective review with a focus on condensed-matter realisations
• Accurate projective two-band description of topological superfluidity in spin-orbit-coupled Fermi gases
• Solutions of the Bogoliubov-de Gennes equation with position dependent Fermi--velocity and gap profiles
• Coexistence of topological and nontopological Fermi-superfluid phases