1107.1960 (Y. Nakashima et al.)

Fermi-surface reconstruction involving two Van Hove singularities across
the antiferromagnetic transition in BaFe2As2    [PDF]

Y. Nakashima, A. Ino, S. Nagato, H. Anzai, H. Iwasawa, Y. Utsumi, H. Sato, M. Arita, H. Namatame, M. Taniguchi, T. Oguchi, Y. Aiura, I. Hase, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki

We report an angle-resolved photoemission study of BaFe2As2, a parent compound of iron-based superconductors. Low-energy tunable excitation photons have allowed the first observation of a saddle-point singularity at the Z point, as well as the Gamma point. With antiferromagnetic ordering, both of these two van Hove singularities come down below the Fermi energy, leading to a topological change in the innermost Fermi surface around the kz axis from cylindrical to tear-shaped, as expected from first-principles calculation. These singularities may provide an additional instability for the Fermi surface of the superconductors derived from BaFe2As2.

View original: http://arxiv.org/abs/1107.1960