▎ 摘　　要

In this work we have theoretically studied the band structure and Landau level spectrum of AB Bernal-stacked twisted double bilayer graphene with Rashba spin???orbit interaction. Using the low energy effective theory, we have studied the flat bands bandwidth as a function of twist angle, inter layer coupling strength, interlayer potential difference, and spin???orbit interaction strength. We find that the tunable Rashba spin???orbit interaction strength enhances the flatness of the flatbands. We further predicted an unusual strong spin polarization and multiple crossings of Landau levels with increasing interlayer coupling, Rashba spin???orbit interaction strength, and external bias voltage.