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Description
Artificial electronic crystals provide a route to engineering both band structure and electron interactions in a highly controllable solid-state system [1]. We realise such crystals by imposing a nanoscale periodic electrostatic potential on a high-mobility two-dimensional electron gas in an ultrashallow GaAs quantum well. The strength of the periodic potential can be continuously controlled by gate voltage, allowing the electronic dispersion to be transformed within a single device from nearly free-electron bands to graphene-like and kagome-like band structures [2].
Magnetotransport measurements directly reveal this reconstruction of the electronic spectrum. As the chemical potential is swept through the artificial bands, reversals of the low-field Hall response track changes in Fermi-surface topology and show good agreement with calculated band structures. At strong modulation, the artificial kagome lattice hosts a narrow electronic band arising from destructive interference of electron wavefunctions. The suppression of kinetic energy in this flat-band regime enhances the relative importance of electron-electron interactions and provides favourable conditions for the emergence of correlated electronic phases [3]. At half filling of the kagome flat band, we observe the emergence of a correlated insulating state unique to the kagome regime. The observed state is consistent with a loop-current Wigner insulator arising from long-range Coulomb interactions and the delocalisation of electrons between neighbouring unoccupied lattice sites.
The ability to continuously tune the band structure and access flat bands through electrical gating within a single device provides a new route to investigating interaction-driven collective quantum states in designer electronic lattices.
References
[1] M. Polini et al., Nature Nanotechnology 8, 625 (2013).
[2] D. Q. Wang et al., Nature Physics (2026).
[3] J.-X. Yin, B. Lian and M. Z. Hasan, Nature 612, 647 (2022).