Fig. 1. Gate-tunable JJ in MATBG.

a Schematic of the measured device and measuring circuit, where V_bias is the source voltage, I is the current through the device, V_xx the voltage drop between the measurement probes, and V_BG (V_TG) correspond to the back (top) gate voltage. The top graphite gates are separated by 150 nm. b Electrostatic simulation profile of carrier density n vs. position x, setting n and carrier density in the junction n_J at different values with a junction length d_J of 100 nm. The inset shows a schematic of the MATBG JJ with two distinct regions created by the gating structure. c Four terminal longitudinal resistance R_xx vs. filling factor υ at different out-of-plane magnetic fields B from 0 mT (black curve) to 300 mT (red curve). d (Top) Magnification of c around the superconducting state −3 < υ < −1.8, where we define three distinct regions with metallic (N), superconducting (SC), and correlated insulator (CI) behavior. (Bottom) $d{V}_{xx}/dI$ vs. I at different n_J, keeping n = −1.72 × 10¹²cm⁻² in the SC state. Dashed green vertical lines mark the position where n_J is no longer in the SC state. e Fraunhofer patterns measured at (left) n_J = −2 × 10¹²cm⁻² (SC/N/SC), (center) −1.72 × 10¹²cm⁻² (SC/SC/SC), and (right) −1.56 × 10¹²cm⁻² (close to SC/CI/SC), respectively. The color dots show the corresponding n_J positions in the dV_xx/dI vs. I map in d bottom. f Positive critical current I_c⁺ vs. B with B sweeping up (blue) and down (red). g dV_xx/dI vs. I at B = 0 mT after applying a pre-magnetizing field B_M = + 50 and −50 mT for the red and blue curve. The shaded gray regions mark the values of current at which the diode behavior is observed.