We have developed a microscopic theory on phonon energy dispersion in chiral crystals within a harmonic approximation. One of the main issues is about the splitting of sound velocity of acoustic phonons with opposite ``crystal'' angular momentum. We have shown that the splitting must be zero even in chiral crystals and the difference starts from the order of at least $k^2$ or higher in their energy dispersion. Splitting is evident for chiral optical phonons, and we have derived a formula for their $k$-linear splitting. Another important finding is about possible interactions of atomic displacements in microscopic models. We have found that antisymmetric interactions of $\mathbf{D} _{ij} \cdot (\mathbf{d} _i \times \mathbf{d} _j) $ type are not allowed in microscopic Hamiltonians for chiral phonons in compatible with the stability against the Nambu-Goldstone mode. We have identified that the splitting in both acoustic and optical modes arises from the harmonic potentials with the electric toroidal quadrupole of $G_{u}$-type symmetry. These constraint are important for modeling real materials. Most of our microscopic calculations have been performed for (quasi-)one-dimensional systems with a trigonal crystal symmetry including Te, but these results generally hold also for other chiral phonon systems.
National Synchrotron Radiation Research Center（国家同步辐射研究中心）；National Tsing Hua University（国立清华大学）；Pohang University of Science and Technology（浦项工科大学）；Rutgers University（罗格斯大学）；Institute of Metal Physics（金属物理研究所）；Ural Federal University（乌拉尔联邦大学）；University of Tokyo（东京大学）；National Yang Ming Chiao Tung University（国立阳明交通大学）
Spin-lattice coupling induced chiral phonons and their signature in Raman Circular Dichroism
Technical University of Munich（慕尼黑工业大学）；Institute for Advanced Study, Technical University of Munich（慕尼黑工业大学高等研究院）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；University of Minnesota（明尼苏达大学）；Imperial College London（伦敦帝国理工学院）
Phonon dispersion, Raman spectra and evidence for spin-phonon coupling in MnV$_2$O$_4$ from first-principles
尖晶石结构中的MnV $_2$ O $_4$已知表现出耦合的轨道和自旋有序，并且其拉曼光谱在其低温相中显示出有趣的异常。为了解释这种行为，涉及耦合自旋和声子的目标，我们确定在这里的自旋-声子耦合MnV $_2$ O $_4$从其声子谱的理论分析和它们的依赖于自旋有序和电子相关性，从第一性原理密度泛函理论计算。使用这些在分析的基础上的朗道类理论，我们发现的机制，在其低温阶段观察到的拉曼异常。
Paul Scherrer Institut（保罗谢勒研究所）；Czech Technical University in Prague（布拉格捷克理工大学）；ESRF - The European Synchrotron（欧洲同步辐射装置）；National Cheng Kung University（国立成功大学）
Dynamical properties of magnetic topological insulator $T$Bi$_{2}$Te$_{4}$ ($T=$Mn, Fe): phonons dispersion, Raman active modes, and chiral phonons study
最近发现的磁性拓扑绝缘体$T$ Bi $_{2}$ Te $_{4}$（$T=$ Mn，Fe）结晶为$R\bar{3}m$菱面体结构，并表现出反铁磁有序。在这里，我们讨论这些化合物的晶格动力学，以确认这些系统的稳定性。我们发现，声子色散不包含软模式，所以这两种化合物是动态稳定的$R\bar{3}m$相。我们进行理论分析的模式活动在$Γ$点的讨论化合物。在拉曼激活模的情况下，我们的结果与实验观察到的频率一致。最后，我们还讨论了实现手征声子的可能性。
Atomic forces by quantum Monte Carlo: application to phonon dispersion calculation
我们首次成功地应用{ \it ab initio}量子Monte Carlo（QMC）框架计算声子色散。基于冻结声子技术，在变分蒙特卡罗（VMC）水平上成功地计算了金刚石的全声子色散。在广义梯度近似下，对密度泛函理论进行了改进，得到了与实验值非常接近的重正化谐波光频。QMC方法成功的关键是减少原子力评估中的统计误差。我们表明，这可以通过使用条件良好的原子基组，通过明确地删除基组冗余，这减少了统计误差的力量高达两个数量级。这导致了负担得起的和准确的QMC声子计算，高达$10^{4}$倍比以前的尝试更有效，并铺平了道路，以新的应用，特别是在相关材料，其中声子已经很难复制到目前为止。
