共振声子：结构有序晶体中的局域化
Resonant phonons: Localization in a structurally ordered crystal
AI总结：
本文提出通过在晶体中引入本征声子纳米谐振器实现确定性声子局域化的新机制，并通过全硅纳米柱膜的分子动力学模拟验证其在设计频率处具有显著空间局域化和最小能量交换，优于安德森局域化。
摘要：
声子局域化是凝聚态物理中影响众多材料性质的一种现象。安德森局域化在无序晶格中引起原子尺度的局域化声子干涉，其影响仅限于波长与随机扰动原胞尺寸相当的高频声子。在此，我们从理论上揭示了一种新的声子局域化形式，其通过在晶体材料中引入本征声子纳米谐振器来实现，这些谐振器的特征尺寸可以小于或大于声子波长，但必须相对小于声子平均自由程。该机制是确定性的，并发生在遍布整个频谱的众多离散窄频带内，其中心频率可通过设计控制。作为演示，我们在室温下对全硅纳米柱膜进行分子动力学模拟，并在非谐声子能带结构中明显出现共振杂化的精确频率处，向底层热化环境施加窄带波包作为激发。与纳米结构不表现出局部共振的其他频率范围相比，可以明确观察到沿输运方向显著的 intrinsic 空间声子局域化。此外，在共振频率处与外部源的能量交换被最小化。最后，我们与安德森局域化进行了直接比较，突出了共振声子在干涉频率极限两侧的优越性。
英文摘要：
Phonon localization is a phenomenon that influences numerous material properties in condensed matter physics. Anderson localization brings rise to localized atomic-scale phonon interferences in disordered lattices with an influence limited to high-frequency phonons having wavelengths comparable to the size of a randomly perturbed unit cell. Here we theoretically reveal a new form of phonon localization induced by augmenting a crystalline material with intrinsic phonon nanoresonators with feature sizes that can be smaller or larger than the phonon wavelengths but must be relatively small compared to the phonon mean free paths. This mechanism is deterministic and takes place within numerous discrete narrow-frequency bands spread throughout the full spectrum with central frequencies controlled by design. For demonstration, we run molecular dynamics simulations of all-silicon nanopillared membranes at room temperature, and apply to the underlying thermalized environment narrowband wave packets as an excitation at precisely the frequencies where resonant hybridizations are evident in the anharmonic phonon band structure. Upon comparison to other frequency ranges where the nanostructure does not exhibit local resonances, significant intrinsic spatial phonon localization along the direction of transport is explicitly observed. Furthermore, the energy exchange with external sources is minimized at the resonant frequencies. We conclude by making a direct comparison with Anderson localization highlighting the superiority of the resonant phonons across both sides of the interference frequency limit.
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