Interaction-induced velocity renormalization in magic angle twisted trilayer graphene

TL;DR

This paper reveals how interactions in magic angle twisted trilayer graphene can significantly renormalize electronic velocities, leading to equalization of Dirac excitations and affecting observable tunneling and transport properties.

Contribution

It introduces a novel interaction-driven velocity renormalization mechanism in twisted trilayer graphene near a quantum critical point, extending understanding of twistronics effects.

Findings

Interaction corrections equalize Dirac velocities in the infrared.

Non-monotonic RG flow dominated by a repulsive fixed point.

Predicted experimental signatures in tunneling and transport measurements.

Abstract

Twistronics heterostructures provide a novel route to control 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 a phase transition which can be described by an Ising Gross-Neveu critical point corresponding, e.g., to the onset of valley Hall or Hall order. While the non-interacting model displays massless Dirac excitations with strongly different velocities, we show that interaction corrections make them equal in the infrared. However, the RG flow of the velocities and of the coupling to the critical bosonic mode is strongly non-monotonic 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.