▎ 摘　　要

Unconventional superconductivity in bilayer graphene has been reported for twist angles theta near the first magic angle and charged electrostatically with holes near half filling of the lower flat bands. A maximum superconducting transition temperature T-C approximate to 1.7 K was reported for a device with theta = 1.05 degrees at ambient pressure and a maximum T-C approximate to 3.1 K for a device with theta = 1.27 degrees under 1.33 GPa hydrostatic pressure. A high-T-C model for the superconductivity is proposed herein, where pairing is mediated by Coulomb coupling between charges in the two graphene sheets. The expression derived for the optimal transition temperature, T-C0 = k(B)(-1)?(|n(opt) - n(0)|/2)(1/2)e(2)/zeta, is a function of mean bilayer separation distance zeta, measured gated charge areal densities n(opt) and n(0) corresponding to maximum T-C and superconductivity onset, respectively, and the length constant ? = 0.00747(2) angstrom. Based on existing experimental carrier densities and theoretical estimates for zeta, T-C0 = 1.94(4) K is calculated for the theta = 1.05 degrees ambient-pressure device and T-C0 = 3.02(3) K for the theta = 1.27 degrees pressurized device. Experimental mean-field transition temperatures T-C(mf) = 1.83(5) K and T-C(mf) = 2.86(5) K are determined by fitting superconducting fluctuation theory to resistance transition data for the ambient-pressure and pressurized devices, respectively; the theoretical results for T-C0 are in remarkable agreement with these experimental values. Corresponding Berezinskii-Kosterlitz-Thouless temperatures T-BKT of 0.96(3) K and 2.2(2) K are also determined and interpreted.