paper

Surface electronic structure and isotropic superconducting gap in (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe

arXiv:1506.02825 · doi:10.1103/PhysRevB.92.060504

Abstract

Using angle-resolved photoemission spectroscopy (ARPES), we revealed the surface electronic structure and superconducting gap of (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe, an intercalated FeSe-derived superconductor without antiferromagnetic phase or Fe-vacancy order in the FeSe layers, and with a superconducting transition temperature ( $T_{c}$ ) $\sim$ 40 K. We found that (Li $_{0.8}$ Fe $_{0.2}$ )OH layers dope electrons into FeSe layers. The electronic structure of surface FeSe layers in (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe resembles that of Rb $_{x}$ Fe $_{2 - y}$ Se $_{2}$ except that it only contains half of the carriers due to the polar surface, suggesting similar quasiparticle dynamics between bulk (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe and Rb $_{x}$ Fe $_{2 - y}$ Se $_{2}$ . Superconducting gap is clearly observed below $T_{c}$ , with an isotropic distribution around the electron Fermi surface. Compared with $A_{x}$ Fe $_{2 - y}$ Se $_{2}$ (\textit{A}=K, Rb, Cs, Tl/K), the higher $T_{c}$ in (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe might be attributed to higher homogeneity of FeSe layers or to some unknown roles played by the (Li $_{0.8}$ Fe $_{0.2}$ )OH layers.

5 pages, 4 figures

Surface electronic structure and isotropic superconducting gap in (Li0.8​Fe0.2​)OHFeSe

Abstract

Surface electronic structure and isotropic superconducting gap in (Li $_{0.8}$ Fe $_{0.2}$ )OHFeSe