论文标题
具有平坦带的二维零材料的光学响应
Optical response of two-dimensional Dirac materials with a flat band
论文作者
论文摘要
已经证明具有平坦带的二维狄拉克材料具有多种不寻常的电子特性，但是这些材料的光学特性的研究较少。利用$α$ - $ \ MATHCAL {t} _3 $ lattice作为一种典型系统，其中$ 0 \leα\ le 1 $是一个可调参数，并且通过两个Dirac Cones的圆锥形交叉路口，$α> 0 $出现了平坦的频段，我们研究了平面零件材料系统的电导率，并研究了单个dirac材料的电导率。由于光导率的假想部分可以对光学响应产生重大影响，这是开发$α$ - $ - $ - $ \ MATHCAL {T} _3 $基于晶格的光学设备的重要因素，因此我们被导致具有真实和想象中的零件的完整电导率。仔细检查公式，我们发现了两个现象。首先，对于在某些范围内的$α$的值，两种类型的光学转换共存：两个狄拉克锥之间，另一个之间从平坦带到一个圆锥体之间，这会产生多频横向电气传播波。其次，对于$α= 1 $，因此准粒子变为伪s-1，平坦到圆锥的过渡会导致散射。这些结果为利用$α$ - $ T_3 $晶格的方式铺平了道路，用于Terahertz频域中的光学设备应用。
Two-dimensional Dirac materials with a flat band have been demonstrated to possess a plethora of unusual electronic properties, but the optical properties of these materials are less studied. Utilizing $α$-$\mathcal{T}_3$ lattice as a prototypical system, where $0\le α\le 1$ is a tunable parameter and a flat band through the conic intersection of two Dirac cones arises for $α> 0$, we investigate the conductivity of flat-band Dirac material systems analytically and numerically. Motivated by the fact that the imaginary part of the optical conductivity can have significant effects on the optical response and is an important factor of consideration for developing $α$-$\mathcal{T}_3$ lattice based optical devices, we are led to derive a complete conductivity formula with both the real and imaginary parts. Scrutinizing the formula, we uncover two phenomena. First, for the value of $α$ in some range, two types of optical transitions coexist: one between the two Dirac cones and another from the flat band to a cone, which generate multi-frequency transverse electrical propagating waves. Second, for $α=1$ so the quasiparticles become pseudospin-1, the flat-to-cone transition can result in resonant scattering. These results pave the way to exploiting $α$-$T_3$ lattice for optical device applications in the terahertz frequency domain.
