Magic-Angle Twisted Bilayer Graphene Superconductivity: Correlated Insulator Phases, Dome-Shaped Tc vs. Carrier Density, and Comparison With Cuprate Phase Diagram at 20 mK

This study investigates superconductivity and correlated insulator phases in magic-angle twisted bilayer graphene as a function of carrier density and temperature, including dome-shaped Tc and comparison with cuprate phase diagram structure within the context of condensed matter physics and 2D materials, an area of growing scientific importance given its implications for unconventional superconductivity mechanism studies, moiré quantum material platform for correlated physics, and 2D superconductor qubit device development. Using dry-stamp van der Waals heterostructure assembly, AFM-guided tear-and-stack TBG fabrication to 1.08 degree, dual-gate electrostatic tuning of carrier density nu=-4 to +4, 4-probe resistance vs. T and nu in dilution refrigerator (Oxford Triton 200), and R vs. T superconducting transition measurement, we examine moiré flat band at magic angle reducing kinetic energy bandwidth to meV scale, enhancing electron-electron interactions and enabling Mott-like correlated insulation at integer moiré band filling (nu=+/-2); superconductivity emerging adjacent to correlated insulator by carrier doping, analogous to cuprate doped-Mott mechanism in 6 magic-angle TBG devices with 1.06-1.10 degree twist angles; 48 gate voltage sweeps per device at 8 temperatures (20-800 mK); 3 devices show both correlated insulator and superconductor phases drawn from Northern Quantum Institute cleanroom with N2-atmosphere glovebox TBG assembly, Oxford Triton dilution refrigerator (base T=12 mK), and Keithley 2636B source-measure for 4-probe resistance at 1 nA excitation. Results indicate that Tc_max = 1.84 K at nu = -2.24 (electron-doped side of correlated insulator); dome-shaped Tc vs. nu with Tc falling to zero by nu=-3.8 and -1.6; correlated insulator resistance peak 84 kOhm at nu=-2; phase diagram qualitatively matches hole-doped cuprate with Tc_max/T* ratio 0.24 (p < 0.001), with Tc_max 1.84K; CI resistance 84 kOhm; Tc/T* ratio 0.24 (cuprate-like) as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to condensed matter physics and 2D materials and carry actionable implications for the design of programs and policies targeting unconventional superconductivity mechanism studies, moiré quantum material platform for correlated physics, and 2D superconductor qubit device development.