Understanding the nematic electronic structure of FeSe and its impact on the superconducting state.

Understanding spontaneous electronic nematic ordering in the iron-based superconductors is an important task in the study of unconventional superconductivity. Currently, however, the origin and mechanism of this nematic state, as well as its relationship to superconductivity, are still a subject of debate, both from an experimental and theoretical point of view. In this talk, I will review the peculiar effect of the nematic state on the electronic structure of FeSe. I will focus on recent ARPES measurements [1,2] which report the loss of an electron pocket at the Fermi surface upon entering the nematic state and show how this puzzling Fermi surface transition can provide direct insight into the mechanism of electronic nematicity, by highlighting the importance of the d_xy orbital in its origin [3].

Furthermore, I will discuss the impact that nematicity has on the superconducting properties of this system. I will show that theoretical simulations, assuming spin-fluctuation mediated superconductivity, can directly reproduce the experimental momentum and orbital dependence of the superconducting gap if that theoretical model incorporates the new experimental observations of the nematic electronic structure, which is only possible if nematicity is considered to be dominant on the d_xy orbital [3,4].

I will end by discussing some recent theoretical insight into how the superconducting state may evolve as nematicity is suppressed, for example across a nematic quantum critical point.


[1] M. D. Watson et. al. New. J. Phys, 19, 103021 (2017)
[2] L. C. Rhodes et. al. Phys. Rev. B, 101, 235128 (2020)
[3] L. C. Rhodes et. al. arXiv:2009.00507 (2020)
[4] L. C. Rhodes et. al. Phys. Rev. B, 98, 180503(R) (2018)