Induced spectral gap and pairing correlations from superconducting proximity effect

Abstract

We theoretically consider superconducting proximity effect, using the Bogoliubov-de Gennes theory, in heterostructure sandwich-type geometries involving a normal s-wave superconductor and a non-superconducting material with the proximity effect being driven by Cooper pairs tunneling from the superconducting slab to the non-superconducting slab. Applications of the superconducting proximity effect may rely on an induced spectral gap or induced pairing correlations without any spectral gap. We clarify that in a non-superconducting material the induced spectral gap and pairing correlations are independent physical quantities arising from the proximity effect. This is a crucial issue in proposals to create topological superconductivity through the proximity effect. Heterostructures of 3D topological insulator (TI) slabs on conventional s-wave superconductor (SC) substrates provide a platform, with proximity-induced topological superconductivity expected to be observed on the "naked" top surface of a thin TI slab. We theoretically study the induced superconducting gap on this naked surface. In addition, we compare against the induced spectral gap in heterostructures of SC with a normal metal or a semiconductor with strong spin orbit coupling and a Zeeman splitting potential (another platform for topological superconductivity). We find that for any model for the non-SC metal (including metallic TI) the induced spectral gap on the naked surface decays as $L^{-3}$ as the thickness ($L$) of the non-SC slab is increased in contrast to the slower $1/L$ decay of the pairing correlations. Our distinction between proximity-induced spectral gap (with its faster spatial decay) and pairing correlation (with its slower spatial decay) has important implications for the currently active search for topological superconductivity and Majorana fermions in various superconducting heterostructures.

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Cited by in corpus (16)

• Superconducting Topological Surface States in Non-centrosymmetric Bulk Superconductor PbTaSe2
• Theory for Spin Selective Andreev Reflection in Vortex Core of Topological Superconductor: Majorana Zero Modes on Spherical Surface and Application to Spin Polarized Scanning Tunneling Microscope Probe
• Full proximity treatment of topological superconductors in Josephson-junction architectures
• Induced Energy Gap in Finite-Sized Superconductor/Ferromagnet Hybrids
• Superconducting proximity effect and order parameter fluctuations in disordered and quasiperiodic systems
• Majorana zero modes in spintronics devices
• Robust and fragile Majorana bound states in proximitized topological insulator nanoribbons
• Competing energy scales in topological superconducting heterostructures
• Proximity effect in a superconductor-topological insulator heterostructure based on first principles
• Superconducting proximity effect in flat band systems
• Low-energy modeling of three-dimensional topological insulator nanostructures
• Proximity effect and spatial Kibble-Zurek mechanism in atomic Fermi gases with inhomogeneous pairing interactions
• Bound fermion states in pinned vortices in the surface states of a superconducting topological insulator: The Majorana bound state
• Phase-controlled spin and charge currents in superconductor-ferromagnet hybrids
• Engineering of many-body Majorana states in a topological insulator/s-wave superconductor heterostructure
• Topological Surface Superconductivity Induced by Hydrostatic Pressure-Enhanced Antisymmetric Spin-Orbit Coupling in Non-Centrosymmetric Superconductor PbTaSe2