论文标题
在二维费米超级流体中的第一和第二声音的传播
Propagation of first and second sound in a two-dimensional Fermi superfluid
论文作者
论文摘要
声音传播是平衡热力学和流体动力传输特性之间相互作用的宏观表现。在这里，对于超低费米的二维系统，我们计算了整个BCS-BEC交叉的第一和第二声速度，并分析了系统对外部扰动的响应。在低温方案中，我们重现了最近的测量[Phys Rev. Lett。 {\ bf 124}，240403（2020）]的第一个声速度，由于密度和熵波动的脱钩，它是由密度探针激发的唯一模式。相反，热扰动仅激发了第二种声音，这对超流体耗竭敏感，在深BCS政权中消失，并在Berezinskii-Kosterlitz-无尽的无限超级流体过渡中不连续跳到零。模式之间的混合仅发生在有限温度的BEC状态下，我们的理论将纯粹的骨效果收敛。
Sound propagation is a macroscopic manifestation of the interplay between the equilibrium thermodynamics and the dynamical transport properties of fluids. Here, for a two-dimensional system of ultracold fermions, we calculate the first and second sound velocities across the whole BCS-BEC crossover and we analyze the system response to an external perturbation. In the low-temperature regime we reproduce the recent measurements [Phys Rev. Lett. {\bf 124}, 240403 (2020)] of the first sound velocity, which, due to the decoupling of density and entropy fluctuations, is the sole mode excited by a density probe. Conversely, a heat perturbation excites only the second sound, which, being sensitive to the superfluid depletion, vanishes in the deep BCS regime, and jumps discontinuously to zero at the Berezinskii-Kosterlitz-Thouless superfluid transition. A mixing between the modes occurs only in the finite-temperature BEC regime, where our theory converges to the purely bosonic results.
