Three- to Two-Dimensional Transition of the Electronic Structure in CaFe2As2 - parent compound for an iron arsenic high temperature superconductor

Abstract

We use angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of CaFe2As2 - parent compound of a pnictide superconductor. We find that the structural and magnetic transition is accompanied by a three- to two-dimensional (3D-2D) crossover in the electronic structure. Above the transition temperature (Ts) Fermi surfaces around Gamma and X points are cylindrical and quasi-2D. Below Ts the former becomes a 3D ellipsoid, while the latter remains quasi-2D. This finding strongly suggests that low dimensionality plays an important role in understanding the superconducting mechanism in pnictides.

Submitted to Phys. Rev. Lett. at 21 January 2009, Accepted for publication at 24 March 2009