Fig. 1: The van der Waals Josephson junction of NbSe2.
From: Field-free Josephson diode effect in NbSe2 van der Waals junction
a The schematic of a typical NbSe2 Josephson junction device, showing the h-BN protective layer, NbSe2 thin flakes, Ti/Au electrodes, and SiO2/Si substrate. Inset, the vertical architecture of junction, consisting of two NbSe2 thin flakes. b Optical micrograph of device 1. Top and bottom NbSe2 flakes are highlighted by red and yellow lines. c Cross-sectional high-angle annular dark-field (HAADF)-scanning transmission electron microscopy (STEM) image of device 1. The top and bottom NbSe2 flakes have the same thickness of around 11 nm. d Atomically resolved HAADF-STEM image of device 1, showing the vicinity of the interface. The distances between Nb layers in NbSe2 crystals and at the interface are 0.63 and 0.97 nm, respectively. e Temperature dependence of resistance measured in device 1 (blue) and device 2 (red). Both devices show a sharp superconducting transition, occurring at 6.5 and 6.6 K, respectively. Inset: an expanded view of the superconducting transition.
