磁性体におけるモノポール結晶の理論的研究

在过去的财政年度，我们完成了两个研究课题，并正在完成其他项目，以准备手稿。在我们以前研究Weyl体系中光致Weyl半金属相和Tomonaga-Luttinger液体的基础上，我们首先继续考虑Weyl半金属体系，求解了Weyl电子被球形阶跃势垒散射的问题。通过调节入射能量和势能半径，可以同时进入准经典和量子态。研究了与远场电流和积分截面有关的传输特性，以揭示优先的前向散射。研究结果将有助于外尔体系的输运研究和电子透镜的应用。我们还研究了外磁场下的Dirac/Weyl半金属纳米线。我们使用几个连续模型来考虑圆柱对称性，这在晶格模型中是很难处理的。我们观察了纳米线拓扑半金属的各种效应，同时，我们也受到最近关于手征晶格亚铁磁体Cu_2OSeO_3中声子的磁手征效应的实验的启发，试图建立一个理论。高分辨率超声实验表明，声速不同的平行和反平行传播相对于外部磁场。非互易性的符号应取决于晶体的手性，并且信号应在低于磁有序温度和更高的超声频率下增强。

In the past fiscal year, we finished two research topics and are finalizing other projects for the sake of manuscript preparation. Following our previous works on photoinduced Weyl semimetal phases and Tomonaga-Luttinger liquid in Weyl systems, we first continue to think on Weyl semimetal systems.We solve the Weyl electron scattered by a spherical step potential barrier. Tuning the incident energy and the potential radius, one can enter both quasiclassical and quantum regimes. Transport features related to far-field currents and integrated cross sections are studied to reveal the preferred forward scattering. The findings will be useful in transport studies and electronic lens applications in Weyl systems.We also study the nanowire Dirac/Weyl semimetals under an external magnetic field. We use several continuum models to take account of the cylindrical symmetry that is formidable to deal with in lattice models. We observe various effects of the nanowire topological semimetal.Meanwhile, motivated by a latest experiment on the magnetochiral effect of phonon in a chiral-lattice ferrimagnet Cu2OSeO3, we are trying to make a theory. High-resolution ultrasound experiments reveal that the sound velocity differs for parallel and antiparallel propagation with respect to the external magnetic field. The sign of the nonreciprocity should depend on the chirality of the crystal and the signal should be enhanced below the magnetic ordering temperature and at higher ultrasound frequencies.