标题： 向玻色-爱因斯坦凝聚体增强磁子通量 显示英文标题

标题： Enhancement of magnon flux toward a Bose-Einstein condensate

摘要： 我们对钇铁石榴石薄膜中角度依赖的磁振子参数泵浦进行了理论和实验相结合的研究，重点研究将参数注入的磁振子转移到光谱最小值的机制，其中发生玻色-爱因斯坦凝聚。 使用经典哈密顿形式，我们分析了参数不稳定性阈值条件作为微波泵浦场与外加磁场之间角度的函数，连续追踪平行泵浦和横向泵浦之间的转换。 我们还描述了两种竞争的四磁振子散射机制，这些机制将参数磁振子转移到其频率谱的底部：逐步的Kolmogorov-Zakharov级联，这适用于所有磁场值，以及动能不稳定性机制，它提供了一种更高效的单步通道，将磁振子直接转移到最低能态，但仅在泵浦角度和外加磁场的特定区域内发生，此时守恒定律允许这种情况。 在实验部分，我们结合微聚焦布里渊光散射光谱和矢量磁铁，实现了在受控泵浦角度下对磁振子种群谱的角度分辨映射。 我们观察到，虽然横向泵浦具有更高的不稳定性阈值，但在光谱最小值处的种群显著强于平行泵浦。 这些观察结果表明，在这种条件下，动能不稳定性通道在将磁振子转移到光谱最小值方面起着主导作用。 这些结果揭示了泵浦几何形状在塑造磁振子分布中的关键作用，并为优化磁振子通量进入凝聚体提供了指导，从而推进了磁绝缘体中磁振子玻色-爱因斯坦凝聚的控制。 显示英文摘要

摘要： We present a combined theoretical and experimental study of angle-dependent parametric pumping of magnons in Yttrium Iron Garnet films, with a focus on the mechanisms that transfer parametrically injected magnons toward the spectral minimum where Bose-Einstein condensation occurs. Using a classical Hamiltonian formalism, we analyze the threshold conditions for parametric instability as a function of the angle between the microwave pumping field and the external magnetic field, continuously tracing the transition between parallel and transverse pumping. We also describe two competing four-magnon scattering mechanisms that transfer parametric magnons toward the bottom of their frequency spectrum: The step-by-step Kolmogorov-Zakharov cascade, which is allowed for all magnetic field values, and the kinetic instability mechanisms that provide a much more efficient single-step channel in transferring magnons directly to the lowest-energy states, but occurs within specific regions of the pumping angle and the external magnetic field where the conservation laws permit it. In the experimental part, we employ microfocused Brillouin light scattering spectroscopy in combination with a vector magnet, allowing for angle-resolved mapping of the magnon population spectrum under controlled pumping angle. We observe that transverse pumping, although characterized by a higher instability threshold, yields a markedly stronger population at the spectral minimum compared to parallel pumping. These observations demonstrate that the kinetic instability channel plays a dominant role in transferring magnons to the spectral minimum under such conditions. These results reveal the crucial role of pumping geometry in shaping the magnon distribution and provide guidelines for optimizing the flux of magnons into the condensate, thereby advancing the control of magnon Bose-Einstein condensation in magnetic insulators.