Circular dichroism (CD) is widely applied in chemistry and biology, because chiral molecules can be detected and distinguished by analyzing the value of CD in the terahertz (THz) spectrum, which covers the characteristic spectrum of semiconductors, plasmas, and biomolecules. However, traditional metal metastructures cannot tune the wavelength of CD peaks continuously without changing the geometric parameters, which limits its practical application. In this paper, a three-layer tunable metastructure is proposed with giant CD in the THz spectrum. This structure consists of a gold substrate and two different bulk Dirac semimetal (BDS) bars. Its CD value up to 0.969 can be obtained by simulation. By adjusting the Fermi energy of BDS, the wavelength of CD peaks is tunable in the range of 12 µm without a change in geometric parameters. Furthermore, a theoretical analysis is used to explain the blueshift of the CD peaks while Fermi energy is increased. Moreover, the effect of some structural changes on CD values has also been studied. This work can pave the way to designing a CD detector or related device in the THz spectrum.

中文翻译：

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可调谐元镜与狄拉克半金属引起的巨大圆二色性

圆二色性（CD）广泛用于化学和生物学领域，因为可以通过分析太赫兹（THz）光谱中CD的值来检测和区分手性分子，太赫兹（THz）光谱涵盖半导体，等离子体和生物分子的特征光谱。但是，传统的金属元结构不能在不改变几何参数的情况下连续调节CD峰的波长，这限制了其实际应用。本文提出了在太赫兹频谱中具有巨型CD的三层可调元结构。该结构由一个金基底和两个不同的块状狄拉克半金属（BDS）棒组成。可以通过仿真获得高达0.969的CD值。通过调节BDS的费米能量，可以在不改变几何参数的情况下将CD峰的波长调整为12 µm。此外，理论分析用于解释费米能量增加时CD峰的蓝移。此外，还研究了某些结构变化对CD值的影响。这项工作可以为设计THz频谱中的CD检测器或相关设备铺平道路。