A. Akrap, Y. M. Dai, W. Wu, S. R. Julian, C. C. Homes
The complex optical properties of a single crystal of hexagonal FeCrAs (T_N ~ 125 K) have been determined above and below T_N over a wide frequency range in the planes (along the b axis), and along the perpendicular (c axis) direction. The optical conductivity reveals an anisotropic Drude-like free-carrier response; however, non-metallic behavior is observed with decreasing temperature. In addition to sharp infrared-active lattice modes, a strong electronic absorption in the mid-infrared at ~0.5 eV is observed for both polarizations. Below T_N, a weak shoulder is observed at ~0.12 eV for both polarizations that is attributed to the partial gapping of the Fermi surface in response to the onset of magnetic order, resulting in a decrease in the free-carrier concentration. Above and below T_N the optical conductivity increases rapidly below ~15 meV, indicating a strong renormalization of the scattering rate and the effective mass, suggesting that the carriers are strongly coupled to low-energy bosonic excitations; however, close to T_N this effect is either suppressed or shifts to very low frequency.
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http://arxiv.org/abs/1307.3528
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