Extended Data Fig. 1: Superconductivity in rhombohedral tetralayer graphene device T2.

a, Optical micrograph and illustration of the structure of rhombohedral tetralayer graphene, in which the electrons are polarized to the layer far away from WSe₂. Scale bar, 3 μm. b, Four-terminal resistance R_xx as a function of n_e and gate displacement field D/ε₀. Four regions show zero R_xx (labelled as SC1–SC4, respectively) and superconductivity. SC1 and SC2 show fluctuations, whereas SC3 and SC4 are smooth. c, Temperature dependence of the four superconducting states, with critical temperatures extracted from the comparison of I–V with the BKT model. See Extended Data Fig. 2. d, Differential resistance dV_xx/dI as a function of current I and out-of-plane magnetic field B_⊥ in the SC3 and SC4 states. Both states show peaks of dV/dI as a signature of superconductivity at small magnetic fields. The superconductivity is killed below 30 mT, similar to that of most graphene-based superconductors. e,f, R_xx and R_xy maps at 0.1 T, extracted by symmetrizing and antisymmetrizing the data taken at B_⊥ = ±0.1 T. The fluctuations in SC1, SC2 and neighbouring states all disappear. In f, SC1 (SC2) is surrounded (neighboured) by states that show anomalous Hall signals. The value of normal Hall signals at the same n_e can be seen in the high-D part of the map. g,h, Magnetic hysteresis scans of R_xy taken at the red and orange circle positions in d, showing loops that are consistent with the anomalous Hall signals in f. i, R_xx map taken at B_⊥ = 1.5 T. The period of quantum oscillations indicates a QM (as labelled by the arrow) that neighbours SC1. Combined with the anomalous Hall signals as shown in f, this QM is a spin-polarized and valley-polarized phase. j, R_xx in SC1 (at n_e = 0.55 × 10¹² cm⁻² and D/ε₀ = 1.02 V nm⁻¹) as a function of time, featuring fluctuations when gate voltages are fixed. k,l, Representative magnetic hysteresis of R_xx taken in SC1 (at n_e = 0.57 × 10¹² cm⁻² and D/ε₀ = 1.05 V nm⁻¹) and SC2 (at n_e = 0.7 × 10¹² cm⁻² and D/ε₀ = 1.16 V nm⁻¹). We note that one of the four terminals was damaged during measurement, resulting in only three-terminal resistance measurement being possible.