Tunable correlations in graphene

Correlation effects in moiré lattices have been explored in different two-dimensional systems, including twisted bilayer graphene. To control these correlated states, the use of degrees of freedom other than those affecting the moiré lattice—for example, the twist angle—are necessary. Pablo Jarillo-Herrero and coworkers fabricate a twisted double bilayer graphene device that is highly sensitive to the application of electric and magnetic fields. They show that the correlated insulator state can be spin-polarized and switched on and off using external fields. The tunability of the band structure in different moiré systems is necessary to gain further insights into the nature of the correlated states in two-dimensional materials.