Ultralow-dissipative conductivity by Dirac fermions in BaFe2_2As2_2

We report on the anomalous behavior of the complex conductivity of BaFe$_{2}$As$_{2}$, which is related to the Dirac cone, in the terahertz (THz)-frequency region. Above the spin-density-wave (SDW) transition temperature, the conductivity spectra follow the Drude model. In the SDW state, the imaginary part of the complex conductivity, $\sigma_2$, is suppressed in comparison to that expected according to the Drude model. The real part, $\sigma_1$, exhibits nearly Drude-like behavior. This behavior (i.e., almost no changes in $\sigma_1$ and the depression of $\sigma_2$) can be regarded as the addition of extra conductivity without any dissipations in the Drude-type conductivity. The origin of this ultralow-dissipative conductivity is found to be due to conductivity contribution from quasiparticles within the Dirac cone. In other words, we are able to observe the dynamics of Dirac fermions through the conductivity spectra of BaFe$_2$As$_2$, clearly and directly.Comment: 5pages, 3 figure

Supplementary Material for: Assessment of Bronchial Obstruction Using Lateral Pressure Measurement during Bronchoscopy

<b><i>Background:</i></b> In patients with bronchial obstruction estimating the location of the maximal obstruction is crucial for guiding interventional bronchoscopy. However, flow-volume curves cannot discriminate between the right and left lungs. <b><i>Objectives:</i></b> The aim of this study was to physiologically evaluate bronchial obstruction during interventional bronchoscopy. <b><i>Methods:</i></b> We prospectively measured lateral airway pressure (P_lat) at either side of the obstruction using a double-lumen catheter (pressure-pressure [P-P] curve) simultaneously to assess the degree of bronchial obstruction in 22 patients. The shape of the P-P curve was assessed to confirm the site of maximal obstruction. <b><i>Results:</i></b> In the experimental study, P_lat was uniform between both bronchi in the normal model. For the unilateral and bilateral obstruction models, a phase shift was only seen for the more obstructed side. In healthy subjects, the angle of the P-P curve was close to 45° and linear in shape. In patients with bronchial obstruction, the angle was much smaller but approached 45° after the bronchoscopic procedure. The degree of bronchial obstruction was significantly correlated with the angle of the P-P curve (<i>r</i> = –0.51, <i>p</i> < 0.01). Dyspnea significantly increased when the airway lumen was obstructed by more than 60% (<i>p</i> < 0.0001), and when the P-P curve appeared loop-shaped (<i>p</i> < 0.01). <b><i>Conclusions:</i></b> The shape of the P-P curve could be used to detect the site of maximal obstruction for the optimal positioning of the stent and assess the need for additional procedures in real time in patients with<i></i> bronchial obstruction