Abstract

Topological semimetals have linear band dispersion around the band crossing which is near the Fermi level. Chiral topological semimetals have no spatial inversion symmetry, and they have non-vanishing second-order optical response. The band structure and nonlinear optical conductivity (NOC) \({\sigma }_{zxy}^{(2)}(0;\omega ,-\omega )\) of the isostructural chiral semimetals RhSn, HfSn, and PdGa are studied by the first-principles calculation in this work. Our calculation demonstrates that the maximal NOC \({\sigma }_{zxy}^{(2)}(0;\omega ,-\omega )\) of chiral semimetals RhSn is about \(\sim 1370\, \upmu \hbox {A/V}^{2}\) under terahertz optical field with photon energy of \(\sim \) 12 meV, while the maximal NOCs \({\sigma }_{zxy}^{(2)}(0;\omega ,-\omega )\) of HfSn and PdGa are \(600 \, \upmu \hbox {A/V}^{2}\) and \(240\, \upmu \hbox {A/V}^{2}\), respectively. The relatively large NOC of RhSn can be interpreted by its multiple band crossing on the Fermi level, while multiple band crossings in the band structures of HfSn and PdGa are not on the Fermi level. Our calculations also reveal that the calculated imaginary part of dielectric function decreases with increasing photon energy, while the absorption coefficient increases with increasing photon energy in the terahertz region. The relatively large NOC makes chiral topological semimetal RhSn suitable for terahertz detection.

Graphic Abstract

中文翻译：

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手性半金属RhSn，HfSn和PdGa的太赫兹非线性光学

摘要

拓扑半金属在能带越过费米能级附近具有线性能带色散。手性拓扑半金属没有空间反转对称性，并且它们的二阶光学响应没有消失。等结构手性半金属RhSn，HfSn和PdGa的能带结构和非线性光导率（NOC）\ {{\ sigma} _ {zxy} ^ {（2）}（0; \ omega，-\ omega）\）为在这项工作中由第一原理计算研究。我们的计算表明手性半金属RhSn的最大NOC \（{\ sigma} _ {zxy} ^ {（2）}（0; \ omega，-\ omega）\）约为\（\ sim 1370 \，\ upmu \ hbox {A / V} ^ {2} \）在太赫兹光场下，光子能量为\（\ sim \） 12 meV，而最大NOCHfSn和PdGa的\（{\ sigma} _ {zxy} ^ {（2）}（0; \ omega，-\ omega）\）是\（600 \，\ upmu \ hbox {A / V} ^ {2 } \）和\（240 \，\ upmu \ hbox {A / V} ^ {2} \）。RhSn的相对较大的NOC可以通过其在费米能级上的多能带交叉来解释，而在HfSn和PdGa的能带结构中的多能带交叉不在费米能级上。我们的计算还表明，在太赫兹区域，介电函数的虚部随光子能量的增加而减小，而吸收系数随光子能量的增加而增加。相对较大的NOC使手性拓扑半金属RhSn适用于太赫兹检测。

图形摘要