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arXiv 1809.10484cond-mat.supr-concond-mat.other
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$^3$ He-B中涡旋的自旋波辐射

Spin wave radiation from vortices in $^3$He-B

S. M. Laine, E. V. Thuneberg

摘要:

本文研究了均匀旋进磁化下超流$^3$ He B相中的涡旋线。磁化对涡旋施加转矩,导致其序参量振荡。这些振荡产生自旋波,这类似于振荡电荷产生电磁辐射。自旋波携带能量,导致系统中的耗散。通过求解自旋动力学方程,计算了自旋波辐射对任意磁化倾斜角和磁场方向以及两种涡旋类型的$^3$ He-B的能量耗散。对于双核涡旋,我们还考虑了辐射的各向异性和耗散对半核扭曲的依赖性。辐射的能量与实验中的温度范围$T \sim 0.5 T_c$。计算的耗散对几个参数的依赖关系与实验符合得很好。结合数值计算的涡结构,辐射理论产生的数量级的实验耗散。与实验结果的一致表明,自旋波辐射是中温区超流$^3$ He-B中涡旋的主要耗散机制。

英文摘要:

We consider a vortex line in the B phase of superfluid $^3$He under uniformly precessing magnetization. The magnetization exerts torque on the vortex, causing its order parameter to oscillate. These oscillations generate spin waves, which is analogous to an oscillating charge generating electromagnetic radiation. The spin waves carry energy, causing dissipation in the system. Solving the equations of spin dynamics, we calculate the energy dissipation caused by spin wave radiation for arbitrary tipping angles of the magnetization and directions of the magnetic field, and for both vortex types of $^3$He-B. For the double-core vortex we also consider the anisotropy of the radiation and the dependence of the dissipation on twisting of the half cores. The radiated energy is compared with experiments in the mid-temperature range $T \sim 0.5 T_c$. The dependence of the calculated dissipation on several parameters is in good agreement with the experiments. Combined with numerically calculated vortex structure, the radiation theory produces the order of magnitude of the experimental dissipation. The agreement with the experiments indicates that spin wave radiation is the dominant dissipation mechanism for vortices in superfluid $^3$He-B in the mid-temperature range.

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