2011/06/30 by T. Hänke, Torben Hänke, Steffen Sykora +15 · 2 citations
Materials Science · Physics and Astronomy · #Condensed matter physics #Fermi level #Iron-based superconductors research #Pairing #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quasiparticle #Scattering #Superconductivity #Superconductivity in MgB2 and Alloys #Symmetry (geometry) #Van Hove singularity #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevlett.108.127001
published as Phys. Rev. Lett. 108, 127001 (2012)
openalex publication_date 2012/03/19 · arxiv created 2012/03/20 · arxiv updated 2012/03/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A crucial step in revealing the nature of unconventional superconductivity is to investigate the symmetry of the superconducting order parameter. Scanning tunneling spectroscopy has proven a powerful technique to probe this symmetry by measuring the quasiparticle interference (QPI) which sensitively depends on the superconducting pairing mechanism. A particularly well-suited material to apply this technique is the stoichiometric superconductor LiFeAs as it features clean, charge neutral cleaved surfaces without surface states and a relatively high T(c)∼18 K. Our data reveal that in LiFeAs the quasiparticle scattering is governed by a van Hove singularity at the center of the Brillouin zone which is in stark contrast to other pnictide superconductors where nesting is crucial for both scattering and s(±) superconductivity. Indeed, within a minimal model and using the most elementary order parameters, calculations of the QPI suggest a dominating role of the holelike bands for the quasiparticle scattering. Our theoretical findings do not support the elementary singlet pairing symmetries s(++), s(±), and d wave. This brings to mind that the superconducting pairing mechanism in LiFeAs is based on an unusual pairing symmetry such as an elementary p wave (which provides optimal agreement between the experimental data and QPI simulations) or a more complex order parameter (e.g., s+id wave symmetry).