论文标题
在BKT过渡的稀释玻色气中的第一和第二声音
First and second sound in a dilute Bose gas across the BKT transition
论文作者
论文摘要
我们研究了使用经典场动力学的Berezinksii-Kosterlitz-thouless（BKT）过渡的二维bose气体中两种声音模式的传播，这是由于Christodoulou等人最近的测量。自然594，191（2021）。基于动态结构因子，我们将两种声音模式识别为过渡下方的Bogoliubov（B）和非Bogoliubov（NB）声音模式，以及在过渡上方的扩散和正常声音模式。 NB声音模式速度高于B声音模式速度，我们称之为声音模式的弱耦合方式。我们通过在实验中驱动系统并用阶梯脉冲扰动来扰动密度来激发声音模式，作为次要比较。与动态结构因子和阶梯脉冲激发的声音结果相比，驱动的响应取决于驱动强度，在过渡附近的高温下，在过渡附近的高温下导致B声音模式的速度更高。我们表明，较高的模式速度在整个过渡过程中的温度依赖性较弱，这与实验观察一致。
We study the propagation of the two sound modes in two-dimensional Bose gases across the Berezinksii-Kosterlitz-Thouless (BKT) transition using classical-field dynamics, which is motivated by recent measurements of Christodoulou et al. Nature 594, 191 (2021). Based on the dynamic structure factor, we identify the two sound modes as the Bogoliubov (B) and the non-Bogoliubov (NB) sound mode below the transition, and as the diffusive and the normal sound mode above the transition. The NB sound mode velocity is higher than the B sound mode velocity, which we refer to as the weak-coupling regime of the sound modes. We excite the sound modes by driving the system as in the experiment and by perturbing the density with a step-pulse perturbation, as a secondary comparison. The driven response depends on the driving strength and results in higher velocities for the B sound mode at high temperatures near the transition, compared to the sound results of the dynamic structure factor and step-pulse excitation. We show that the higher mode velocity has a weak temperature dependence across the transition, which is consistent with the experimental observation.
