Distinct Fermi Surface Topology and Nodeless Superconducting Gap in (Tl0.58Rb0.42)Fe1.72Se2 Superconductor

TL;DR

This study uses high-resolution ARPES to reveal a unique Fermi surface topology and a nodeless superconducting gap in (Tl0.58Rb0.42)Fe1.72Se2, offering new insights into iron-based superconductor mechanisms.

Contribution

It reports a distinct Fermi surface topology and superconducting gap structure in (Tl0.58Rb0.42)Fe1.72Se2, different from other iron-based superconductors.

Findings

Two electron-like Fermi surface sheets around Γ point

Nearly isotropic superconducting gap of ~12 meV at M point

Nearly isotropic superconducting gap of ~15 meV near Γ point

Abstract

High resolution angle-resolved photoemission measurements have been carried out to study the electronic structure and superconducting gap of the (Tl$_{0.58}$Rb$_{0.42}$)Fe$_{1.72}$Se$_2$ superconductor with a T$_c$=32 K. The Fermi surface topology consists of two electron-like Fermi surface sheets around $\Gamma$ point which is distinct from that in all other iron-based compounds reported so far. The Fermi surface around the M point shows a nearly isotropic superconducting gap of $\sim$12 meV. The large Fermi surface near the $\Gamma$ point also shows a nearly isotropic superconducting gap of $\sim$15 meV while no superconducting gap opening is clearly observed for the inner tiny Fermi surface. Our observed new Fermi surface topology and its associated superconducting gap will provide key insights and constraints in understanding superconductivity mechanism in the iron-based superconductors.