Abstract
The symmetries of superconducting gap functions remain an important question of iron-based superconductivity. Motivated by the recent angle-resolved photoemission spectroscopic measurements on iron-chalcogenide superconductors, we investigate the influence of pairing symmetries on the topological surface state. If the surface Dirac cone becomes gapped in the superconducting phase, it implies magnetization induced from time-reversal symmetry breaking pairing via spin-orbit coupling. Based on the crystalline symmetry constraints on the Ginzburg-Landau free energy, the gap function symmetries are among the possibilities of $A_{1g(u)}\pm iA_{2g(u)}$, $B_{1g(u)}\pm iB_{2g(u)}$, or, $E_{g(u)}\pm i E_{g(u)}$. This time-reversal symmetry breaking effect can exist in the normal state very close to $T_c$ with the relative phase between two gap functions locked at $\pm \frac{\pi}{2}$. The coupling between magnetization and superconducting gap functions is calculated based on a three-orbital model for the band structure of iron-chalcogenides. This study provides the connection between the gap function symmetries and topological properties of the surface state.
Highlights
The symmetries of superconducting gap functions remain an important issue in iron-based superconductivity
Several theoretical studies suggest that s± and dx2−y2 pairings are nearly degenerate in the iron-pnictide superconductors [26,34], leading to the possibility of a novel time-reversal (TR) symmetry-breaking pairing s± + idx2−y2 [35]
It was proposed that a resonance mode carrying the B1g symmetry [35,36], which can be detected via Raman spectroscopy [37], exists if the s± and dx2−y2 pairings are nearly degenerate
Summary
Pairing symmetry and topological surface state in iron-chalcogenide superconductors. Motivated by the recent angle-resolved photoemission spectroscopic measurements of iron-chalcogenide superconductors, we investigate the influence of pairing symmetries on the topological surface state. If the surface Dirac cone becomes gapped in the superconducting phase, it implies magnetization induced from time-reversal symmetry-breaking pairing via spin-orbit coupling. Based on the crystalline symmetry constraints on the Ginzburg-Landau free energy, the gap function symmetries are among the possibilities of A1g(u) ± iA2g(u), B1g(u) ± iB2g(u), or Eg(u) ± iEg(u). This time-reversal symmetry-breaking effect can exist in the normal state very close to
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have