A. Gauthier | Searcharxiv

arXiv2020

Low work function in the 122-family of iron-based superconductors

We determine the work functions of the iron arsenic compounds $A$Fe$_2$As$_2$ ($A=\mathrm{Ca, Ba, Cs}$) using photoemission spectroscopy to be 2.7 eV for CaFe$_2$As$_2$, 1.8 eV for BaFe$_2$As$_2$, and 1.3 eV for CsFe$_2$As$_2$. The work functions of these 122 iron-based superconductors track those of the elementary metal $A$ but are substantially smaller. The most likely explanation of this observation is that the cleaving surface exposes only half an $A$-layer. The low work function and good photoemission cross section of BaFe$_2$As$_2$ and CsFe$_2$As$_2$ enable photoemission even from a common white LED light.

cond-mat.str-el↗

arXiv2017

3D nature of ZrTe$_5$ band structure measured by high-momentum-resolution photoemission spectroscopy

We have performed a systematic high-momentum-resolution photoemission study on ZrTe$_5$ using $6$ eV photon energy. We have measured the band structure near the $Γ$ point, and quantified the gap between the conduction and valence band as $18 \leq Δ\leq 29$ meV. We have also observed photon-energy-dependent behavior attributed to final-state effects and the 3D nature of the material's band structure. Our interpretation indicates the gap is intrinsic and reconciles discrepancies on the existence of a topological surface state reported by different studies. The existence of a gap suggests that ZrTe$_5$ is not a 3D strong topological insulator nor a 3D Dirac semimetal. Therefore, our experiment is consistent with ZrTe$_5$ being a 3D weak topological insulator.

cond-mat.mtrl-sci↗