Encapsulating high-temperature superconducting twisted van der Waals heterostructures blocks detrimental effects of disorder

Twisted cuprate van der Waals heterostructures with controlled Josephson coupling

“…The main feature that can be deduced from the color plots is that I c R N , at which the inner peaks of each dV /dI appear, sensitively decreases at twist angles close to 45°. For the two JJs with θ = 0°, the critical currents normalized by the corresponding junction area are j c = 0.9 kA/cm 2 and j c = 1.0 kA/cm 2 at 10 K [37], comparable to j c of intrinsic junction in BSCCO crystals, which ranges at that temperature from 0.17 kA/cm 2 to 1.7 kA/cm 2 , depending on the number of junctions along the c-axis [42]. Differently from BSCCO JJs investigated in previous studies [27,28], the dV /dI at θ = 0°i n Fig 4(a) does not show hysteresis, suggesting a barrier with low capacitance.…”

“…Here, we build several JJs with different twist angles using the recently established dry and cryogenic stacking technique. We encapsulate the junction region with an insulating crystal in order to block the detrimental effects of disorder throughout the device fabrication [37], especially during the evaporation of electrical contacts in a chamber with the base pressure of 1 × 10 −6 mbar. Under this vacuum condition, the reactivity of water molecules is still too high and an additional encapsulating layer is essential to preserve a pristine interface between the thin BSCCO crystals.…”