  Understanding and tuning correlated states is of great interest and
significance to modern condensed matter physics. The recent discovery of
unconventional superconductivity and Mott-like insulating states in magic-angle
twisted bilayer graphene (tBLG) presents a unique platform to study correlation
phenomena, in which the Coulomb energy dominates over the quenched kinetic
energy as a result of hybridized flat bands. Extending this approach to the
case of twisted multilayer graphene would allow even higher control over the
band structure because of the reduced symmetry of the system. Here, we study
electronic transport properties in twisted trilayer graphene (tTLG, bilayer on
top of monolayer graphene heterostructure). We observed the formation of van
Hove singularities which are highly tunable by twist angle and displacement
field and can cause strong correlation effects under optimum conditions,
including superconducting states. We provide basic theoretical interpretation
of the observed electronic structure.
