Non-Fermi liquids in van der Waals multilayers from subsystem symmetry breaking

This study explores the spontaneous breaking of subsystem symmetry in a layered system of two-dimensional Fermi liquid metals, each exhibiting subsystem number conservation symmetry. In this symmetry-broken phase, the resulting Goldstone modes couple to the electron current flowing perpendicular to the layers. This coupling, which persists at small momentum transfers, promotes the formation of a marginal Fermi liquid state. We propose an experimental setup to realize this effect using two-dimensional multilayer van der Waals heterostructures. Through self-consistent mean-field calculations, we analyze the subsystem symmetry-broken metallic state and its physical properties, notably a pronounced logarithmic divergence in specific heat at low temperatures, driven by subsystem symmetry. We also identify distinctive qualitative signatures of this state in quantum oscillations with varying magnetic field orientation.