Chiral Topological Pair-Density Wave in Rhombohedral Graphene

We will first introduce the interacting phase diagram of rhombohedral graphene, along with the effects of the small yet comparable spin-orbit coupling and valley-interchange interaction, for which our theoretical predictions have shown excellent agreement with experimental observations [1, 2]. We will then focus on an unprecedented superconducting state experimentally observed in the quarter-metal phase of tetra-, penta-, and hexa-layer graphene. In particular, we will show that this state emerges from a parent state that is single-spin, single-valley, single-band, and single-Fermi-pocket in nature, and is most likely a chiral topological pair-density wave characterized by an ultra-small Fermi pocket and an ultra-large pairing momentum [3]. This novel state exhibits three defining features [3]: a 2D periodic modulation of the pairing phase; Majorana zero modes localized at edges, vortices, and pairing-phase dislocations; and an anomalous spin-polarized intrinsic superconducting diode effect.

[1] J. Yang, C. Yoon et al., Impact of spin-orbit coupling on superconductivity in rhombohedral graphene. Nature Materials 24, 1058–1065 (2025).

[2] Anna M Seiler, C. Yoon et al., Layer-selective spin-orbit coupling and strong correlation in bilayer graphene. 2D Materials 12, 035009 (2025).

[3] C. Yoon, T. Xu, Y. Barlas, and F. Zhang. Quarter-metal superconductivity in rhombohedral graphene. arXiv:2502.17555 (2025).