Photon absorption of two-dimensional nonsymmorphic Dirac semimetals
Photon absorption of two-dimensional nonsymmorphic Dirac semimetals
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DOI：
10.1103/physrevb.105.085101
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发表时间：
2021-05
影响因子：
3.7
通讯作者：
Amarnath Chakraborty;G. Bian;G. Vignale
中科院分区：
文献类型：
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作者：
Amarnath Chakraborty;G. Bian;G. Vignale
美国密苏里州哥伦比亚市，密苏里州大学物理与天文系，Amarnath Chakraborty，卞光，Giovanni维尼亚莱（日期：2022年2月10日）摘要二维狄拉克半金属由于其线性能量色散和非平凡的Berry相而引起了人们的极大关注。这些材料是罕见的，因为节点带结构对诸如自旋轨道耦合（SOC）的扰动是脆弱的。最近，有报道称，即使存在SOC，非对称晶格也在某些高对称动量周围具有对称增强的类狄拉克带色散。在这里，我们计算了具有各向异性狄拉克锥的非对称半金属的光学吸收谱，其中费米速度沿着x和y方向不同。计算结果表明，光吸收系数强烈地依赖于各向异性因子和光子偏振。通过旋转后者，可以改变吸收系数超过一个数量级，从而产生双折射。当施加磁场时，吸收系数还取决于内部参数，我们称之为能带结构的“混合角”。因此，该参数可用于实验研究。我们进一步发现，面内磁场在使系统无间隙的同时，可以在联合态密度中诱发Van-Hove奇异性：这会导致一个方向的奇异频率处的光吸收显着增强偏振方向，但对于正交方向则不然，这使得光学性质更加强烈地依赖于偏振和各向异性。这些结果表明，一个非常纯粹的非对称二维狄拉克半金属可以是一个很好的候选材料的可调谐磁光器件。
Amarnath Chakraborty,∗ Guang Bian, and Giovanni Vignale† Department of Physics and Astronomy, University of Missouri, Columbia, Missouri, USA (Dated: February 10, 2022) Abstract Two-dimensional Dirac semimetals have attracted a great deal of attention because of their linear energy dispersion and non-trivial Berry phase. These materials are rare because the nodal band structure is fragile against perturbations such as the spin-orbit coupling (SOC). Recently, it has been reported that nonsymmorphic crystal lattices possess symmetry-enforced Dirac-like band dispersion around certain high symmetry momenta even in the presence of SOC. Here we calculate the optical absorption spectra of the nonsymmorphic semimetals, which hosts anisotropic Dirac cones, with different Fermi velocities along the x and y directions. Our calculations show that the optical absorption coefficient depends strongly on the anisotropy factor and the photon polarization. By rotating the latter, one can change the absorption coefficient by more than an order of magnitude, giving rise to birefringence. When a magnetic field is applied, the absorption coefficient also depends on an internal parameter, which we term the “mixing angle” of the band structure. This parameter becomes therefore accessible to experimental investigation. We further find that an in-plane magnetic field, while leaving the system gapless, can induce a Van-Hove singularity in the joint density of states: this causes a significant enhancement of the optical absorption at the frequency of the singularity for one direction of polarization but not for the orthogonal one, making the optical properties even more strongly dependent on polarization and anisotropy. These results suggest that a very pure nonsymmorphic 2D Dirac semimetal can be an excellent candidate material for tunable magneto-optic devices.