Zihan Cheng, UT-Austin

"Non-Fermi liquid from moiré Hofstadter phonons"

Abstract: Landau Fermi-liquid theory successfully describes the low-energy behavior of most metals, but when metalic states are strongly coupled to soft collective modes, some non-Fermi-liquid behaviors will occur. The detailed behavior of these non-Fermi-liquid systems remains poorly understood due to the absence of naturally controlled theoretical calculations or efficient numerical methods, and limited ability to tune the electron density or interactions in the underlying host materials.. We theoretically explore two-dimensional (2D) moiré heterostructures in lattice-commensurate magnetic fields as platforms for quantum simulation of a paradigmatic model of non-Fermi-liquid physics: a Fermi surface coupled to a fluctuating gauge field. In these moiré Hofstadter systems, long-wavelength acoustic phonons exhibit singular interactions with electrons analogous to those of electrons with 2D gauge fields. This leads to a breakdown of Fermi-liquid theory at low temperatures. We show that a combination of large moiré unit-cell size, tunable Fermi-surface topology, and enhanced coupling to interlayer sliding modes enhances these effects by over many orders of magnitude compared with bulk crystals, placing them within experimental reach.