Fig. 4: Mott metal-insulator transition controlled via tip-induced gating.
From: Local gate control of Mott metal-insulator transition in a 2D metal-organic framework
a–c Schematics and energy diagrams of tunnelling and charging processes at a double-barrier tunnel junction (DBTJ), consisting of STM tip, vacuum barrier (vac.), MOF, hBN barrier, and Cu(111), for small, intermediate (int.), and large tip-sample distances (Δz + z0). When Vb is applied, voltage drop at MOF location enables tip-controlled charging, energy level shifts, and gating of MOF transitions, from (correlated) Mott insulator to metal to trivial insulator. These schematics qualitatively illustrate our proposed physical mechanism of tip-induced gating. d dI/dV spectra at MOF DCA lobe site, at hBN/Cu(111) moiré wire, for different Δz + z0 (z0 given by STM setpoint Vb = 10 mV, It = 10 pA). Purple circles: MOF charging peak. Red squares: intrinsic electronic state at MOF band edge. Spectra normalised and offset for clarity. e Vcharge (purple circles in d) and Vstate (red squares in d) as a function of Δz. Black solid lines: global fits to Eqs. (1) and (2). f dI/dV signal at Fermi level (Vb = 0) as a function of Δz, from d. Increased dI/dV(Vb = 0) indicates metallic phase at intermediate Δz + z0. Inset: STM image of MOF on hBN/Cu(111) showing site (blue triangle marker) where dI/dV(Δz) measurements were performed (Vb = − 1 V, It = 10 pA, scale bar: 2 nm).
