Fig. 2
From: Optical anisotropy in optimally doped iron-based superconductor
Stress dependence of the optical anisotropy of Ba0.6K0.4Fe2As2 at T < Tc: a, b Representative data of the optical reflectivity (R(ω)) at 10 K for the p-loop experiment after a ZPC protocol along the a- and b-axis (Ra and Rb, respectively, Fig. 1) in the spectral range below 1400 cm−1. c The reflectivity ratio RRatio = Ra/Rb. d, e Real part σ1(ω) of the optical conductivity, achieved through KK transformation of the data in panels a and b. f The so-called dichroism \({\mathrm{\Delta }}\sigma _1(\omega ) = \sigma _1^a(\omega ) - \sigma _1^b(\omega )\) at 10 K within the p-loop experiment. c, f focus the attention to the FIR energy interval 200–1000 cm−1, where the reversible optical anisotropy upon sweeping p is discovered. A first-neighbor interpolation procedure is used in order to generate the color maps. Released pressures are denoted by ‘(r)’. The thick dotted line in all panels marks p = 1.2 bar (i.e., at saturation)
