AI 中文总结
本研究揭示菱方石墨烯中可通过层/轨道依赖相互作用、能带手性与狄拉克费米面拓扑，在保持时间反演和反演对称性下产生Kekulé配对密度波超导，绘制了相图并确定了BKT转变温度。
AI 中文摘要
在弱耦合条件下，有限动量超导通常与费米面的时间反演或反演对称性破缺相关。本研究表明，菱方多层石墨烯中的晶格尺度配对密度波序可由依赖于层/轨道的配对相互作用、能带手性以及以狄拉克点为中心的费米面拓扑结构产生，且同时保持上述两种对称性。利用平均场理论，我们将有限动量扇区$Q = \pm 2 K_{D}$与$Q=0$超导态进行对比，发现符号相反的层依赖相互作用（$V_{1A}=-V_{JB}=-|V|$）更有利于形成具有质心动量（$Q=\pm 2 K_D$）的谷内Kekulé态。在存在保持时间反演与反演对称性的Kane-Mele质量（$\lambda$）时，该态仅在临界载流子密度（$n^{crit}_{K}(\lambda,J)$）以上出现。两种超导凝聚体表现出相反的手性，$K_D(-K_D)$谷对应$J(-J)$，从而保持了时间反演与反演对称性。我们绘制了相图，分析了临界温度$T_c$对手性指数$J$和$\lambda$的依赖关系，还计算了Kekulé超导态的超流刚度，进而确定了Berezinskii-Kosterlitz-Thouless（BKT）转变温度。研究结果表明，在具有能带手性的体系中，依赖轨道的相互作用会在保持时间反演与反演对称性的狄拉克材料中促进有限动量配对。
英文摘要
At weak coupling, finite-momentum superconductivity is typically associated with broken time-reversal or inversion symmetry of the Fermi surface. Here, we show that lattice-scale pair-density-wave order in rhombohedral multilayer graphene can arise from layer/orbital-dependent pairing interactions, band chirality, and Dirac-point-centered Fermi surface topology while preserving both symmetries. Using mean-field theory and comparing finite momentum sectors $Q = \pm 2 K_{D}$ with the $ Q = 0$ superconducting state, we find that layer-dependent interactions of opposite signs ($V_{1A}=-V_{JB}=-|V|$) favor an intra-valley Kekulè state with center-of-mass momentum ($ Q=\pm 2 K_D$). In the presence of a time-reversal and inversion symmetry-preserving Kane-Mele mass ($λ$), this state appears only above a critical carrier density ($n^{crit}_{K}(λ,J)$). The two superconducting condensates exhibit opposite chirality, $J(-J)$ for $K_D(-K_D) $ valleys, thereby preserving time-reversal and inversion symmetry. We map the phase diagram and analyze the dependence of $T_c$ on the chirality index $J$ and $λ$. We also evaluate the superfluid stiffness in the Kekulè superconducting state, thereby determining the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. Our results show that orbital-dependent interactions in the presence of band chirality favor finite-momentum pairing in time-reversal and inversion symmetric Dirac materials.
Comments10 pages
