Phenomenological theory of the anomalous normal-state transport properties of iron pnictides

We employ the phenomenological theory of the quasiparticle relaxation based on the simplified two-band description and the spin-fluctuation mediated interband coupling to analyze recent normal-state transport data in electron-doped iron pnictides, in particular the $\text{Ba}{\left({\text{Fe}}_{1-x}{\text{Co}}_x\right)}_2{\text{As}}_2$ family. The temperature and doping dependence of the resistivity, thermopower, and the Hall constant are evaluated. We show that their anomalous behavior emerging from experiments can be consistently described within the same framework assuming also “marginal,” i.e., non-Fermi-liquid-like spin fluctuations provided, however, that the interband coupling is quite strong. We also show that a large thermopower as experimentally observed results from an asymmetric energy-dependent quasiparticle relaxation rate and due to the semimetallic character of both bands.

Figure 1

(Color online) Electron-band QP damping ${\Gamma }^e\left(\omega \right)$ for various $T$ for the intermediate doping. Horizontal line represents the chosen hole damping ${\Gamma }_0^h$.

Figure 2

(Color online) The resistivity $\rho \left(T\right)/{\rho }_0$ (full line; left scale) and the thermopower $S\left(T\right)/S_0$ (dashed line; right scale) for the intermediate electron-doped IPs.

Figure 3

(Color online) (a) Resistivity $\rho \left(T\right)/{\rho }_0$, (b) thermopower $S\left(T\right)/S_0$, and (c) the Hall constant $R_H\left(T\right)/R_H^0$ for different Fermi-liquid temperatures $T^{\ast }$ and fixed concentrations $x_e=0.2,x_h=0.08$.

Figure 4

(Color online) (a) Resistivity $\rho \left(T\right)/{\rho }_0$, (b) thermopower $S\left(T\right)/S_0$, and (c) the Hall constant $R_H\left(T\right)/R_H^0$ for $T^{\ast }=0$ and various electron doping $\delta n_e$ with respect to the parent $x_e^0=x_h^0=0.15$ case.