  Materials with flat electronic bands often exhibit exotic quantum phenomena
owing to strong correlations. Remarkably, an isolated low-energy flat band can
be induced in bilayer graphene by simply rotating the layers to 1.1$^{\circ}$,
resulting in the appearance of gate-tunable superconducting and correlated
insulating phases. Here, we demonstrate that in addition to the twist angle,
the interlayer coupling can also be modified to precisely tune these phases. We
establish the capability to induce superconductivity at a twist angle larger
than 1.1$^{\circ}$ $-$ in which correlated phases are otherwise absent $-$ by
varying the interlayer spacing with hydrostatic pressure. Realizing devices
with low disorder additionally reveals new details about the superconducting
phase diagram and its relationship to the nearby insulator. Our results
demonstrate twisted bilayer graphene to be a uniquely tunable platform for
exploring novel correlated states.
