Strange metal and exotic non-Fermi liquids at two-dimensional van Hove singularity

Non-Fermi liquids, particularly the universal strange metal, are ubiquitously observed in strongly correlated materials, that includes the high-$T_c$ cuprates, ruthenate oxides and twisted bilayer graphenes. The unprecedent tunablity of these two-dimensional (2D) systems provides access towards the Lifshitz transition where the Fermi surface exhibits van Hove singularity (VHS) saddle points. Despite extensive investigation on the ordering instabilities, the critical phenomenon induced by the VHS are rarely explored. Here, we investigate the NFL behaviors at Lifshitz transition in the 2D magnetic heterostructure interface, where the Fermi surface undergoes a convex-to-concave topological transition. We uncover an exotic NFL phase at the VHS that dominates over other Fermi surface points in the low-energy limit. At finite energies, it crossovers to the well-known marginal Fermi liquid (MFL). In the finite-temperature regimes, we demonstrate that the universal strange metal transport emerges both in the MFL phase, and unexpectedly, in the exotic NFL phase which is induced by solely by the spatially uniform Yukawa interaction. This non-vanishing optical conductivity is largely attributed to the Galilean invariance breaking at VHS. Furthermore, we propose that the non-magnetic ARPES can directly probe the exotic NFL features at heterostructure interface. Our findings explore the interplay of VHS in lower dimension, disorder and strong interactions, which paves a novel path to study the high-$T_c$ superconductivity, 2D magnetism and spintronics.
Comment: 44 pages, 8 figures