Friedel oscillations in two-dimensional materials with inverted bands and Mexican-hat dispersion

Abstract

We study Friedel oscillations (FOs) in two-dimensional topological materials with Mexican hat band dispersion, which attract great interest due to the bunch of its inherent non-trivial features, including the Van Hove singularity, doubly connected Fermi surface, non-trivial quantum-geometric properties, and the presence of states with negative effective mass. These factors are found to lead to a three-mode structure of the FOs. One of the modes, arising from electron transitions between the Fermi contours, has an unexpectedly large amplitude. The evolution of the amplitudes of all modes with Fermi energy is largely determined by the interplay of three main factors: intra-contour and inter-contour electron transitions, the quantum metric of the basis states, and the electron–electron interaction. We traced the role of each factor in the formation of the FO pattern and identified the corresponding features of the FO evolution.