Effect of the tetrahedral distortion on the electronic properties of
iron-pnictides
The characteristic building blocks of iron pnictides are FeAs layers. Fe atoms
form a square lattice. Each Fe atom is surrounded by four As atoms in an almost
tetrahedral coordination (see Figure below).
The layer structure is different to the
CuO2 planes in the cuprates. Arsenic can be
substituted by other pnictogen atoms like phosporus in LaFePO.
The angle formed by the Fe and As atoms differs among compounds and also depends on
doping. Experimentally it has been suggested that there is a correlation
between the critical temperature and this angle, with a higher superconducting critical temperature corresponding to a regular tetrahedron geometry. Recently, we have studied the effect of the tetrahedral distortion
on the electronic properties of these compounds.
We have analyzed the angle-dependence of the band structure within a tight
binding model in which hopping between Fe atoms is assumed to be mediated by As
and its magnitude is calculated within the Slater-Koster
framework, which captures the correct symmetry properties of the bands. In a two
and three orbital model the density of states and the band structure are very
sensitive to changes in the angle formed by the As-Fe bonds. Since there is a
strong dependence of the hoppings
on this angle this result is important for both the weak and the strong
coupling scenarios proposed to explain magnetism and
superconductivity in these systems.
For more information look at:
' Effect of the tetrahedral distortion on the electronic properties of
iron-pnictides ',
María José
Calderón, Belén Valenzuela, and Elena Bascones.
New J. Phys. 11, 013051 (2009).
' Tight binding model for iron pnictides ',
María José
Calderón, Belén Valenzuela, and Elena Bascones.
arXiv:0907.1259; accepted in Phys. Rev. B.