发表机构
Uppsala University; University of Alberta（乌普萨拉大学; 阿尔伯塔大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究提出二维超导体边缘存在超导派尔斯不稳定性，其通过超导科恩异常产生边缘配对密度波使安德烈夫束缚态能隙化，为超导体自发平移对称性破缺提供新机制。
AI 中文摘要
派尔斯不稳定性是凝聚态物理中的基础机制，它展示了电子-声子相互作用如何将简单金属转变为具有新晶格周期性的绝缘态。在一维（1D）金属中，派尔斯不稳定性源于波矢Q=2k_F（连接费米点）处增强的电子响应，产生了科恩异常：同一波矢下声子模式的软化。该模式的凝聚会产生标志性的派尔斯周期性晶格畸变和电荷密度波（CDW），从而使电子能谱产生能隙。在此，我们展示了二维（2D）超导体边缘处的类似不稳定性，其中色散的安德烈夫束缚态（ABS）在±k_c处拥有玻戈留波夫费米点。连接波矢Q=2k_c处增强的准粒子响应直接与配对涨落耦合，产生了超导科恩异常：同一波矢下配对模式的软化。该模式的凝聚会产生边缘配对密度波（PDW），从而使ABS产生能隙。我们将此称为超导派尔斯不稳定性，并确定了使其成为可能的边界准粒子结构。作为具体实现，我们考虑了一个方形晶格扩展哈伯德模型，其混合对称性s+d+ip态在有限边缘动量处具有零能交叉的色散ABS。通过自洽玻戈留波夫-德热纳（BdG）计算，我们证明了序参量会形成边缘PDW，其波矢由超导科恩异常设定，可使ABS交叉产生能隙。我们的结果确定了超导体中自发平移对称性破缺的新机制。由于这种超导派尔斯机制不需要广泛的零能平带或拓扑保护的边缘态，它可能广泛适用于非常规超导体。
英文摘要
The Peierls instability is a foundational mechanism in condensed matter physics, showing how the electron--phonon interaction can transform a simple metal into an insulating state with a new lattice periodicity. In a one-dimensional (1D) metal the Peierls instability follows from the enhanced electronic response at wavevector $Q=2k_F$ (connecting the Fermi points) producing a Kohn anomaly: a softening of the phonon mode at the same wavevector. Condensation of this mode then generates the tell-tale Peierls periodic lattice distortion and charge-density wave (CDW) that gaps the electronic spectrum. Here we show an analogous instability at the edge of a two-dimensional (2D) superconductor, where a dispersing Andreev bound state (ABS) hosts Bogoliubov Fermi points at $\pm k_c$. The enhanced quasiparticle response at the connecting wavevector $Q=2k_c$ couples directly to pairing-fluctuations and produces a superconducting Kohn anomaly: a softening of a pairing mode at the same wavevector. Condensation of this mode then generates an edge pair-density wave (PDW) that gaps the ABS. We refer to this as a superconducting Peierls instability and identify the boundary quasiparticle structure that enables it. As a concrete realization, we consider a square-lattice extended Hubbard model whose mixed-symmetry $s+d+ip$ state hosts a dispersing ABS with zero-energy crossings at finite edge momenta. Using self-consistent Bogoliubov--de Gennes (BdG) calculations we show that the order parameter develops an edge PDW, with the wavevector set by the superconducting Kohn anomaly, that gaps the ABS crossings. Our results identify a novel mechanism for spontaneous translation-symmetry breaking in a superconductor. As this superconducting Peierls mechanism does not require an extensive zero-energy flat band or topologically protected edge states, it may apply broadly to unconventional superconductors.
CommentsMain text: 11 pages, 5 figures; Methods: 7 pages, 1 figure; Supplementary Material: 12 pages, 5 figures
