# Van Hove singularities, chemical pressure and phonons: an angle-resolved photoemission study of KFe$_2$As$_2$ and CsFe$_2$As$_2$

@article{Richard2018VanHS, title={Van Hove singularities, chemical pressure and phonons: an angle-resolved photoemission study of KFe\$\_2\$As\$\_2\$ and CsFe\$\_2\$As\$\_2\$}, author={Pierre Richard and Ambroise van Roekeghem and X. Shi and Priyanka Seth and Baijiang Lv and T. K. Kim and X.-H. Chen and Silke Biermann and Hong Ding}, journal={arXiv: Superconductivity}, year={2018} }

We report an angle-resolved photoemission spectroscopy (ARPES) study of KFe$_2$As$_2$ and CsFe$_2$As$_2$, revealing the existence of a van Hove singularity affecting the electronic properties. As a result of chemical pressure, we find a stronger three-dimensionality in KFe$_2$As$_2$ than in CsFe$_2$As$_2$, notably for the 3$d_{z^2}$ states responsible for the small three-dimensional hole-like Fermi surface pocket reported by quantum oscillations. Supported by first-principles calculations, our…

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