Non-Hermitian zero-energy pinning of Andreev and Majorana bound states in superconductor-semiconductor systems

Abstract

The emergence of Majorana bound states in finite length superconductor-semiconductor hybrid systems has been predicted to occur in the form of oscillatory energy levels with parity crossings around zero energy. Each zero-energy crossing is expected to produce a quantized zero-bias conductance peak but several studies have reported conductance peaks pinned at zero energy over a range of Zeeman fields, whose origin, however, is not clear. In this work we consider superconducting systems with spin-orbit coupling under a Zeeman field and demonstrate that non-Hermitian effects, due to coupling to ferromagnet leads, induce zero-energy pinning of Majorana and trivial Andreev bound states. We find that this zero-energy pinning effect occurs due to the formation of non-Hermitian spectral degeneracies known as exceptional points, whose emergence can be controlled by the interplay of non-Hermiticity, the applied Zeeman field, and chemical potentials. Moreover, depending on the non-Hermitian spatial profile, we find that non-Hermiticity changes the single point Hermitian topological phase transition into a flattened zero energy line bounded by exceptional points from multiple low energy levels. This seemingly innocent change notably enables a gap closing well below the Hermitian topological phase transition, which can be in principle simpler to achieve. Furthermore, we reveal that the energy gap separating Majorana and trivial Andreev bound states from the quasicontinuum remains robust for the values that give rise to the zero-energy pinning effect. While reasonable values of non-Hermiticity can be indeed beneficial, very strong non-Hermitian effects can be detrimental as it might destroy superconductivity. Our findings can be therefore useful for understanding the zero-energy pinning of trivial and topological states in Majorana devices.

10 pages, 5 figures. Published version

References in corpus (27)

• Non-Hermitian Physics
• The physics of exceptional points
• Non-Hermitian topological phenomena: A review
• Transport spectroscopy of NS nanowire junctions with Majorana fermions
• Towards a realistic transport modeling in a superconducting nanowire with Majorana fermions
• A Majorana smoking gun for the superconductor-semiconductor hybrid topological system
• Observing Majorana Bound States in p-wave Superconductors Using Noise Measurements in Tunneling Experiments
• SNS junctions in nanowires with spin-orbit coupling: role of confinement and helicity on the sub-gap spectrum
• Flat Band in Disorder Driven Non-Hermitian Weyl Semimetals
• Disorder-induced zero-bias peaks in Majorana nanowires
• Nontopological zero-bias peaks in full-shell nanowires induced by flux tunable Andreev states
• Majorana splitting from critical currents in Josephson junctions
• Majorana nanowires for topological quantum computation
• A perspective on semiconductor-based superconducting qubits
• Theory of Majorana zero modes in unconventional superconductors
• Zero-energy pinning from interactions in Majorana nanowires
• Distinguishing trivial and topological zero energy states in long nanowire junctions
• Exceptional odd-frequency pairing in non-Hermitian superconducting systems
• Pinning of Andreev bound states to zero energy in two-dimensional superconductor-semiconductor Rashba heterostructures
• Zero-frequency supercurrent susceptibility signatures of trivial and topological zero-energy states in nanowire junctions
• Bulk Bogoliubov Fermi arcs in non-Hermitian superconducting systems
• Near zero-energy Caroli-de Gennes-Matricon vortex states in the presence of impurities
• Mitigating disorder-induced zero-energy states in weakly-coupled semiconductor-superconductor hybrid systems
• Anomalous Andreev Spectrum and Transport in Non-Hermitian Josephson Junctions
• Exceptional degeneracies in non-Hermitian Rashba semiconductors
• Fractional Josephson effect versus fractional charge in superconducting-normal metal hybrid circuits
• Dissipation Enhanced Unidirectional Transport in Topological Systems

Cited by in corpus (14)

• Superconducting phenomena in systems with unconventional magnets
• Non-Hermitian phase-biased Josephson junctions
• Non-Hermitian multiterminal phase-biased Josephson junctions
• Entanglement measures of Majorana bound states
• Interplay between Majorana and Shiba states in a minimal Kitaev chain coupled to a superconductor
• Non-Hermitian minimal Kitaev chains
• Fingerprint of Non-Hermiticity in d-wave Altermagnet
• Andreev non-Hermitian Hamiltonian for open Josephson junctions from Green's functions
• Odd-frequency pairing due to Majorana and trivial Andreev bound states
• Non-Hermitian superconducting diode effect
• Anomalous proximity effect under Andreev and Majorana bound states
• Non-Hermitian skin effect and electronic nonlocal transport
• Supercurrent from the imaginary part of the Andreev levels in non-Hermitian Josephson junctions
• Odd-frequency Pairing in Josephson Junctions Coupled by Magnetic Textures