Fig. 3: Variation of Mott energy gap in DCA3Cu2 MOF induced by hBN/Cu(111) moiré modulation of local work function.
From: Local gate control of Mott metal-insulator transition in a 2D metal-organic framework
a STM image of MOF (Vb = −1 V, It = 10 pA). White dashed circles (P): hBN/Cu(111) moiré pores, separated by wire (W). Grey arrow indicates moiré period λ ≈ 12.5 nm. b dI/dV spectra acquired at MOF Cu sites, at positions indicated by coloured markers in a (tip 190 pm further from STM setpoint Vb = 10 mV, It = 10 pA). Energy gap Eg ≈ 200 meV at P regions, vanishing at W region (LHBM: lower Hubbard band maximum; UHBM: upper Hubbard band minimum). c Sinusoidal variation of work function, ΔΦ = ΔEvac − EF (Evac: vacuum energy level), across hBN/Cu(111) moiré domain with periodicity λ ≈ 12.5 nm30, affecting the MOF electron filling. d Spectral functions A(E) calculated via DMFT (U = 0.65 eV, t = 0.05 eV) for isolated uniform DCA3Cu2, for different values of EF. We account for experimental corrugation ΔΦ by varying EF sinusoidally with an amplitude of 0.2 eV as per c (see Methods). e Experimental dI/dV signal at Fermi level (Vb = 0) as a function of x position, from b. Increased dI/dV(Vb = 0) indicates metallic phase. f, g Experimental (red; b) and DMFT (blue; d) LHBM (squares), UHBM (circles), and energy gap Eg (triangles), as a function of x in a (experiment) or corresponding EF (DMFT).
