Wang Jia, Liu Xia-Ji, Hu Hui
Centre for Quantum Technology Theory, Swinburne University of Technology, Melbourne 3122, Australia.
Phys Rev Lett. 2022 Apr 29;128(17):175301. doi: 10.1103/PhysRevLett.128.175301.
We present the Ramsey response and radio-frequency spectroscopy of a heavy impurity immersed in an interacting Fermi superfluid, using the exact functional determinant approach. We describe the Fermi superfluid through the conventional Bardeen-Cooper-Schrieffer theory and investigate the role of the pairing gap on quasiparticle properties revealed by the two spectroscopies. The energy cost for pair breaking prevents Anderson's orthogonality catastrophe that occurs in a noninteracting Fermi gas and allows the existence of polaron quasiparticles in the exactly solvable heavy impurity limit. Hence, we rigorously confirm the remarkable features such as dark continuum, molecule-hole continuum, and repulsive polaron. For a magnetic impurity scattering at finite temperature, we predict additional resonances related to the subgap Yu-Shiba-Rusinov bound state, whose positions can be used to measure the superfluid pairing gap. For a nonmagnetic scattering at zero temperature, we surprisingly find undamped repulsive polarons. These exact results might be readily observed in quantum gas experiments with Bose-Fermi mixtures that have a large-mass ratio.
我们使用精确的泛函行列式方法，展示了浸没在相互作用费米超流体中的重杂质的拉姆齐响应和射频光谱。我们通过传统的巴丁 - 库珀 - 施里弗理论描述费米超流体，并研究配对能隙对这两种光谱揭示的准粒子性质的作用。配对破坏的能量成本阻止了在非相互作用费米气体中发生的安德森正交性灾难，并允许在精确可解的重杂质极限中存在极化子准粒子。因此，我们严格证实了诸如暗连续谱、分子 - 空穴连续谱和排斥极化子等显著特征。对于有限温度下的磁性杂质散射，我们预测了与亚能隙汤川 - 芝 - 鲁西诺夫束缚态相关的额外共振，其位置可用于测量超流体配对能隙。对于零温度下的非磁性散射，我们惊人地发现了无阻尼的排斥极化子。这些精确结果可能很容易在具有大质量比的玻色 - 费米混合物的量子气体实验中观察到。
