Tunable Extended Magnetic Non‐Fermi Liquid in Twisted Double Bilayer Graphene With Aligned hBN

Abstract

ABSTRACT Twisted graphene heterostructures with highly tunable flat‐band electronic structures serve as an ideal platform for exploring novel correlated and topological quantum phases. While previous efforts have focused on the twist angle, the lattice alignment with the hBN substrate is another crucial parameter that breaks symmetry and reconstructs the band structure. However, its underlying mechanisms remain insufficiently explored, and extending it to a wider class of twisted graphene systems is urgently needed to uncover more exotic quantum phenomena. Here, we report the observation of tunable extended non‐Fermi liquid behavior in twisted double bilayer graphene (TDBG) encapsulated by aligned hBN layers. This NFL phase emerges on the hole‐doped side of the correlated insulating state near charge neutrality, spanning a broad range of carrier densities and exhibiting a carrier density–dependent resistance exponent. Notably, the NFL phase can re‐enter a correlated insulating state at higher doping levels. Combined with temperature‐dependent resistance, magnetotransport, and differential resistance measurements, these findings support a scenario where strong quantum fluctuations may emerge from the interplay between localized and itinerant carriers. Our work establishes a highly tunable platform beyond conventional frameworks to investigate the organizing principles of non‐Fermi liquid physics manifested in diverse behaviors.