Overdamped van der Waals Josephson junctions by area engineering

Abstract: Van der Waals (vW) Josephson junctions (JJs) realized by stacking materials such as few-layered NbSe2, offers a new landscape to realize superconducting quantum devices with superior properties owing to its crystalline nature and defect-free junctions. For quantum technology, overdamped JJs are highly sought-after, whose realization demands precise control of junction capacitance by engineering the junction area using microfabrication techniques. NbSe2 is highly reactive and susceptible to damage during microfabrication processes. In this manuscript, we demonstrate both underdamped and overdamped NbSe2-NbSe2 JJs by controlling the junction area. We devise a minimally invasive microfabrication procedure, post-junction formation, to precisely control the junction area. The McCumber parameter characterizing the damping is extracted from the electrical transport measurements down to 130 mK. The results show that our sample fabrication recipe has preserved the material qualities and paved the way for the realization of scalable JJ devices on NbSe2 and similar systems.