Volume 88, Number 3, November 2009
Article Number 37004
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 19 November 2009
EPL, 88 (2009) 37004
DOI: 10.1209/0295-5075/88/37004

Polaron-like conduction in iron pnictides of the Ln-1111 and Æ-122 families

M. Núñez-Regueiro

Institut Néel, Centre National de Recherches Scientifiques and Université Joseph Fourier BP166 cedex 9, 38042 Grenoble, France, EU

received 2 July 2009; accepted in final form 9 October 2009; published November 2009
published online 19 November 2009

The examination of the electrical resistivities of iron pnictides shows that they follow a $\rho \sim T\,{\rm exp}(E_{a}/k_{B}T)$ temperature dependence. The activation energies Ea show a linear behaviour with the critical temperatures of the spin density waves (SDW), T*, as both vary with pressure. The slope matches the ratio SDW gap to T*, while the intercept can be related to the transition temperature of the lattice distortion, T0. An adapted Landau free energy predicts the observed order of the transitions, according to which is higher, T* or T0. We discuss our analysis within the framework of polarons.

72.15.-v - Electronic conduction in metals and alloys.
74.90.+n - Other topics in superconductivity.

© EPLA 2009