Interaction induced velocity renormalization in magic-angle twisted trilayer graphene

Twistronics heterostructures allow to reduce the electronic single particle velocity and thereby to engineer strong effective interactions. Here we show that the reverse may also hold, i.e. that these interactions strongly renormalize the band structure. We demonstrate this mechanism for mirror-symmetric magic-angle twisted trilayer graphene at charge neutrality and in the vicinity of an Ising Gross-Neveu critical point corresponding to the onset of valley Hall or Hall order. While the non-interacting model displays fermionic modes with strongly different velocities, the infrared physics is determined by a fixed point with equal velocities. However, the RG flow of the relative velocities and of the relative coupling to the critical bosonic mode is strongly non-monotonous and dominated by the vicinity of a repulsive fixed point. We predict experimental consequences of this theory for tunneling and transport experiments and discuss the expected behavior at other quantum critical points, including those corresponding to intervalley coherent ordering.