Is rhombohedral graphene a chiral topological superconductor
In plain words
Tetralayer and pentalayer graphene superconduct out of a state in which electron spins and valleys (the two inequivalent momentum regions where graphene's low-energy electrons are found) are aligned, and the superconductor shows magnetic hysteresis, suggesting pairs that rotate in one direction (chiral pairing).
Precise statement
Han et al. (Nature 643, 654, 2025) found two superconducting states with $T_c$ up to 300 mK at $n$ down to $2.4e11\,\mathrm{cm}^{-2}$ in rhombohedral tetralayer and pentalayer graphene without moire, emerging from a spin- and valley-polarized quarter metal and showing anomalous-Hall hysteresis. Determine the pairing symmetry and whether the state is topological, i.e., its Bogoliubov Chern number and number of chiral Majorana edge modes. An answer gives both with direct evidence.
What would settle it
Thermal Hall conductance $\kappa_{xy}/T$ at $T << T_{\mathrm{c}}$ or edge tunnelling revealing chiral Majorana modes, plus phase-sensitive Josephson tests.
Status in the literature
Unverified note
2025 transport gives evidence of time-reversal breaking; no edge-mode or phase-sensitive measurement as of 2026.