Sonderseminar: Explore flat-bands with artifical atomic lattices

  • Datum:

    Mittwoch, 23.07.2025, 14.00 Uhr

  • Referent:

    Prof. Haifeng Ding
    Department of Physics, Nanjing University, China

  • Abstract: Flat-bands yield electrons in the band with vanishing group velocity and divergent effective mass, promoting strong correlation physics. Previous investigations only found a rather limited number (~10) of 2D flat-band lattices with the number of the sites in an unit cell less than 10. In addition, the flat bands of many well-known lattices, such as Lieb and kagome lattices are obtained with the nearest neighbor (NN) hopping only. The adding of the higher order NN hopping, however, strongly influences the flatness of the band and the originally predicted flat-band is no longer flat. In this talk, I will present our recent studies of flat-bands with artifical atomic lattices. In Fe adatom on Ag(111), we found a surface state assisted long range hopping between ada- toms, where the hopping shows an inverse square dependence with their separation rather than the commonly thought explonential one [1]. With the same system, we demonstate a band compression effect with can effectly compress the bandwidth of a particular band and convert it to a flat band [2]. Moreover, we show a general method for realizing flat bands based on mathematical optimization and symmetry analysis. The method allows us to find over 1000 flat-band lattices, implying flat-band structures are far more a- bundant than previously thought [3]. These findings suggest that the artificial atomic structures can serve as an interesting playground to explore the rich flat-band physics.

     

    [1] X. Li et al., Chin. Phys. Lett., 39, 057301, (2022)
    [2] R. Yan et al., Phys. Rev. B, 108, 075153, (2023)
    [3] H. Li et al., Phys. Rev. Lett., 134, 076402, (2025)