论文标题
从弹性旋转到声子自旋：对称性和基本关系
From Elastic Spin to Phonon Spin: Symmetry and Fundamental Relations
论文作者
论文摘要
这项工作主要基于自2020年春季以来在汤吉大学的研究生讲座。我们首先重新审视弹性自旋和轨道角动量[Proc。纳特。学院。科学。美国115，9951（2018）]，但对各向异性系统的更一般性通过将Noether定理应用于弹性Lagrangian，并在现场理论中应用对称论点。然后，发现了弹性能通量和弹性自旋之间的基本关系。在特定情况下，波自旋与能量通量和动量的涡度密切相关。其次，我们通过将第二个量化应用于弹性场，从弹性自旋前进，重新审视声子自旋[Fizika Tverdogo Tela 3，2160（1961）]。我们表明，未覆盖的声子自旋（一种极化的弹性振动量子）通常不限于横向声子模式，而是适用于通用的声子模式，例如纵向声子模式，表面声子模式和杂交声子模式，被视为模式干涉的结果。弹性自旋和声子自旋起源于时域中场极化的局部旋转，而不是空间域中位移或速度的局部循环（涡度）。希望目前的结果能够提高对声子自旋和弹性自旋的基本理解，并以多种自由度促进杂交量子传感和技术的自旋语音。
This work is mainly based on postgraduate lectures at Tongji University since 2020 spring. We firstly revisit the elastic spin and orbital angular momentum [Proc. Natl. Acad. Sci. USA 115, 9951 (2018)] but more general for anisotropic systems by applying Noether's theorem to the elastic Lagrangian and by applying the symmetry argument in the field theory. Then, fundamental relations between elastic energy flux and elastic spin are uncovered. In particular cases, the wave spin is closely related to the vorticity of energy flux and momentum. Secondly, we move forward from the elastic spin to revisit the phonon spin [Fizika Tverdogo Tela 3, 2160 (1961)] by applying the second quantization to elastic fields. We show that the uncovered phonon spin, a polarized elastic-vibration quanta, is generally not restricted to transverse phonon modes, but applying to general phonon modes, such as the longitudinal phonon modes, surface phonon modes, and hybridized phonon modes, regarded as a consequence of mode interferences. The elastic spin and phonon spin originate from the local rotating of the field polarization in time domain, not the local circulation (vorticity) of displacement or velocity in space domain. It is hopeful that the present results could advance the fundamental understanding of phonon spin and elastic spin, and promote the spin phononics for hybrid quantum sensing and technology with multiple degrees of freedom.
