交变磁纳米线中的一阶拓扑 FFLO 转变与超导二极管符号反转
First-Order Topological FFLO Transition and Superconducting Diode Sign Reversal in Altermagnetic Nanowires
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中文总结 AI 辅助
研究交变磁纳米线中拓扑 FFLO 态，发现与零净磁化 d 波交变磁体接近的自旋轨道耦合纳米线，通过一阶相变实现该态，伴有超导二极管效应，金兹堡 - 朗道理论解释机制，提供无场途径并确定输运指纹。
中文摘要 AI 辅助
传统上，富尔德 - 费雷尔 - 拉金 - 奥夫钦尼科夫（FFLO）态通过有限磁化驱动的二阶相变出现。本文表明，与净磁化为零的 d 波交变磁体接近的自旋轨道耦合纳米线，可通过一阶相变实现拓扑 FFLO 态，其特征为尖锐的符号反转超导二极管效应。交变磁场产生能带分辨的竞争配对通道，形成双谷自由能景观，其全局最小值会不连续切换。这导致一阶拓扑 FFLO 转变，同时库珀对振幅和有限质心动量发生跃变。这种不连续的拓扑重构显著提高了二极管效率，并在转变过程中驱动特征性的尖锐符号反转。金兹堡 - 朗道理论解释了这种奇异现象的机制。我们的结果提供了一条无场交变磁途径来实现拓扑 FFLO 态，并确定了它们的直接输运指纹。
英文摘要
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state conventionally emerges via a second-order phase transition driven by finite magnetization. Here we show that a spin-orbit-coupled nanowire proximitized to $d$-wave altermagnets -- with zero net magnetization -- can realize topological FFLO states through a first-order transition, marked by a sharp sign-reversing superconducting diode effect. The altermagnetic field generates band-resolved competing pairing channels, giving rise to a double-valley free energy landscape whose global minimum switches discontinuously. It consequently leads to a first-order topological FFLO transition with simultaneous jumps in the Cooper pairing amplitude and finite center-of-mass momentum. Remarkably, this discontinuous topological reconfiguration substantially enhances the diode efficiency and drives a characteristic sharp sign reversal across the transition. The mechanism of such exotic phenomena is captured by Ginzburg--Landau theory. Our results provide a field-free altermagnetic route to topological FFLO states and identify their direct transport fingerprint.
