We analyze the electronic structure of different surface terminations for infinite-layer nickelates. Surface NiO2 layers are found to be buckled, in contrast to planar bulk layers. While the rare-earth terminated surface fermiology is similar to the bulk limit of the nickelates, the NiO2 terminated surface band structure is significantly altered, originating from the effect of absence of rare-earth atoms on the crystal field splitting. Contrary to the bulk Fermi surfaces, there are two Ni-3d Fermi pockets, giving rise to enhanced spectral weight around the Mˉ point in the surface Brillouin zone. From a strong-coupling analysis, we obtain dominant extended s-wave superconductivity for the surface layer, as opposed to d-wave for the bulk. This finding distinguishes the nickelates from isostructural cuprates, where the analogous surface pairing mechanism is less pronounced. Our results are consistent with region-dependent gap structures revealed in recent STM measurements and provide an ansatz to interpret experimental data of surface-sensitive measurements on the infinite-layer nickelates.
@article{arxiv.2008.06009,
title = {Surface $s$-wave superconductivity for oxide-terminated infinite-layer nickelates},
author = {Xianxin Wu and Kun Jiang and Domenico Di Sante and Werner Hanke and A. P. Schnyder and Jiangping Hu and Ronny Thomale},
journal= {arXiv preprint arXiv:2008.06009},
year = {2020}
}