Encapsulating High‐Temperature Superconducting Twisted van der Waals Heterostructures Blocks Detrimental Effects of Disorder

Abstract

High‐temperature cuprate superconductors based van der Waals (vdW) heterostructures hold high technological promise. One of the obstacles hindering their progress is the detrimental effect of disorder on the properties of the vdW‐devices‐based Josephson junctions (JJs). Here, a new method of fabricating twisted vdW heterostructures made of Bi2Sr2CuCa2O8+δ, crucially improving the JJ characteristics and pushing them up to those of the intrinsic JJs in bulk samples, is reported. The method combines cryogenic stacking using a solvent‐free stencil mask technique and covering the interface by insulating hexagonal boron nitride crystals. Despite the high‐vacuum condition down to 10−6 mbar in the evaporation chamber, the interface appears to be protected from water molecules during the in situ metal deposition only when fully encapsulated. Comparing the current–voltage curves of encapsulated and unencapsulated interfaces, it is revealed that the encapsulated interfaces’ characteristics are crucially improved, so that the corresponding JJs demonstrate high critical currents and sharpness of the superconducting transition comparable to those of the intrinsic JJs. Finally, it is shown that the encapsulated heterostructures are more stable over time.

2D High-Temperature Superconductor Integration in Contact Printed Circuit Boards

“…At the top and bottom surfaces of the BSCCO crystal, a subunit cell degraded region (dark area) can be observed due to a 30 min exposure of the flake to the glovebox atmosphere (Ar: 99.999%, O 2 ≤ 0.1 ppm, H 2 O ≤ 0.1 ppm) between the crystal exfoliation and the stacking of the membrane on top of it. In our system, we are able to preserve interface superconductivity and crystalline order in regions exposed less than 1 min to the Ar atmosphere at cryogenic temperatures. , A pristine BSCCO/Au interface can thus be created by a quick stacking of the circuit on top of the crystal, which is, however, beyond the scope of the present study.…”

“…Additionally, twisted interfaces between cuprate crystals have been proposed as an adaptable platform for Josephson junctions with controllable coupling, − which is a desirable feature for quantum applications. Thin BSCCO films promise to become an important platform for quantum sensors and detectors since bolometers fabricated from thin structured BSCCO crystals demonstrated a high level of single-photon sensitivity above 25 K. , Yet, the main challenge for building these structures is to maintain the superconducting phase of thin BSCCO crystals while integrating them into an electrical circuit, as the oxygen dopants are mobile at temperatures exceeding 200 K. , Furthermore, thin BSCCO flakes easily react with water leading to structural changes and modification of the oxygen doping level, which is crucial since altering the doping can drive the BSCCO film into an insulating phase. − The preservation of interface superconductivity of the BSCCO crystal has been recently achieved by means of a cryogenic exfoliation technique combined with a solution-free stencil mask approach, enabling the fabrication of electrical devices entirely in an inert atmosphere. ,, The bottleneck hindering the realization of functional integrated circuits based on cuprate superconductors is the metallization of atomically thin crystals. The previously mentioned stencil mask approach enables the realization of simple electrical contacts in a single-layer geometry through the thermal evaporation of relatively low melting metals, such as gold, while providing a resolution down to 1 μm .…”

Clean Transfer of Two-Dimensional Materials: A Comprehensive Review

“…This is because the pressing of the elastomer stamp during the transfer process can lead to deformation of the supporting elastomer by a stress that is much higher than the strength of 2D materials, , and the incomplete release of 2D materials exists owing to the strong adhesion between supporting layer and 2D materials (Figure e,f). Although some works have applied temperature control to kinetically control the adhesion of elastomer stamps, − the complete release of 2D materials on arbitrary substrate still remains a challenge.…”

Optically Probing Unconventional Superconductivity in Atomically Thin Bi2Sr2Ca0.92Y0.08Cu2O8+δ

“…1,9−11 To mitigate these issues, stencil mask lithography and limited-heating evaporation have been employed to reduce the damage of electrical contact fabrication in relatively thick flakes. 10,12,13 Additionally, a cold welding approach has been developed to preserve the ML sample quality, 1 although this method requires implementing a series of intricate processes in a stringent environment. In this study, we propose an alternative approach to investigate the superconductivity in atomically thin Bi2212 using ultrafast optical pump−probe spectroscopy, a noninvasive probe with micrometer-sized spatial resolution that allows us to study the interaction of 2D-HTSCs with different local environments.…”

“…Recent experiments have revealed that novel phenomena such as the interfacial Josephson effect and superconducting diode effect can emerge in artificially twisted Bi2212 stacks. − Theoretically, it has been predicted that such twisted stacks can host more exotic physics, including topological superconductivity with broken time-reversal symmetry. − However, fabricating high-quality cuprate devices and probing their intrinsic properties through transport measurements remain challenging. One of the primary challenges lies in the susceptibility of atomically thin Bi2212 to degradation during conventional nanofabrication processes due to oxygen dopant loss and reaction with moisture. ,− To mitigate these issues, stencil mask lithography and limited-heating evaporation have been employed to reduce the damage of electrical contact fabrication in relatively thick flakes. ,, Additionally, a cold welding approach has been developed to preserve the ML sample quality, although this method requires implementing a series of intricate processes in a stringent environment. In this study, we propose an alternative approach to investigate the superconductivity in atomically thin Bi2212 using ultrafast optical pump–probe spectroscopy, a noninvasive probe with micrometer-sized spatial resolution that allows us to study the interaction of 2D-HTSCs with different local environments.…”