Band engineering of semiconductor artificial graphene and exploration of flat band physics(*)*

Semiconductor artificial graphene (AG) has been realized on 2D electron systems in GaAs quantum wells subjected to a lateral potential modulation with honeycomb symmetry [1, 2]. Tunability of the AG band structure is a key property of the artificial systems. Here, we present effective band engineering of semiconductor AG with multiple control knobs that offer flexible and effective exclusive tunability of electron properties. Using the cutting-edge fabrication technology, we fabricated small-period triangular antidot lattices with different honeycomb lattice periods (35 nm to 45 nm) and various AG potentials. The M-point gap, which reveals key characteristics of the AG band structure, was measured by intersubband excitations using resonant inelastic light scattering (RILS) at low temperature. We found that the M-point gap could be tuned from 0.5 meV to 1.2 meV, with the band dispersion near the M point evolving from the Dirac-like case to flat band. Emerging flat-band physics in such tunable system will be discussed. [1] S. Wang, et al. Nature Nanotech. 13, 29 (2018). [2] L. Du, et al., Nature Commun. 9, 3299 (2018).