Infrared spectroscopic study of topological material BaMnSb2

A detailed infrared optical spectrum of the new topological material BaMnSb<sub>2</sub> has been measured at temperatures ranging from 7 K to 295 K. As temperature decreases, plasma minimum a clear blue shift in reflectivity spectrum, indicating that carrier density changes with temperature. In real part conductivity <inline-formula><tex-math id="M1">\begin{document}$\sigma_{1}(\omega)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20220011_M1.jpg"/><graphic xlink:href="10-20220011_M1.png"/></alternatives></inline-formula>, two linearly-increased components can be identified, but neither their extrapolation pass through origin, which proves gapped Dirac dispersion near Fermi level. Comparing theoretical calculation by using first-principles methods, onset these are good agreement band structures. addition, range constant is found id="M2">\begin{document}$\sigma_{1}(\omega)$\end{document}</tex-math><alternatives><graphic xlink:href="10-20220011_M2.jpg"/><graphic xlink:href="10-20220011_M2.png"/></alternatives></inline-formula>, cannot described well Drude-Lorentz model. Therefore, we introduce frequency-independent component fit id="M3">\begin{document}$\sigma_{1}(\omega)$\end{document}</tex-math><alternatives><graphic xlink:href="10-20220011_M3.jpg"/><graphic xlink:href="10-20220011_M3.png"/></alternatives></inline-formula> successfully. However, different nodal-line semimetal YbMnSb<sub>2</sub> shares same fitting results as crystal structure, small proportion id="M4">\begin{document}$\sigma_{1}(\omega)$\end{document}</tex-math><alternatives><graphic xlink:href="10-20220011_M4.jpg"/><graphic xlink:href="10-20220011_M4.png"/></alternatives></inline-formula>. Through and analysis, attribute surface state BaMnSb<sub>2</sub>.