High-performance ultraviolet (UV) photodetectors play a very important role in many fields, especially in the military, biomedical and other fields. [1]In recent years, many studies have realized ultraviolet photodetectors of 2D layered materials, overcome the problems of traditional ultraviolet detectors that are large and use high voltages. [1]Up to now, most of these works use atomically thin layers and simple p-n van der Waals (vdW) heterostructures, which have difficulty meeting the conditions of high sensitivity and ultrafast response at the same time. we report the double p-n van der Waals (vdW) heterostructure built on a large electrode. The two p-n junctions connected in parallel were proven to be able to effectively separate photo-generated carriers and suitable for ultraviolet light. This new type of photodetector exhibits competitive performance, including high R up to 254.8 A/W under UV light, and fast photoresponse τr = 7.9 μs and τd = 3.9 μs. These results provide an ideal platform for realizing highly sensitive UV photodetectors.

Vortex dynamics has attracted tremendous attention for both fundamental physics and applications of type-II superconductors. However, methods to detect local vortex motion or vortex jump with high sensitivity are still scarce. Here, we fabricated soft point contacts on the clean layered superconductor 2H–NbSe2, which are demonstrated to contain multiple parallel micro-constrictions by scanning electronic microscopy. Andreev reflection spectroscopy was then studied in detail for the contacts. Differential conductance taken at fixed bias voltages was discovered to vary spontaneously over time in various magnetic fields perpendicular to the sample surface. The conductance variations become invisible when the field is zero or large enough, or parallel to the sample surface, which can be identified as the immediate consequence of vortex motion across a finite number of micro-constrictions. These results demonstrate point contact Andreev reflection spectroscopy to be a new potential way with a high time resolution to study the vortex dynamics in type-II superconductors.

Unconventional superconductivity in the quasi-two-dimensional cuprates and iron-based superconductors has attracted great attention in these years. Recently, the discovery of the Cr-based ternary compounds has aroused the research upsurge for the possible spin-triplet superconductivity revealed from the bulk samples. Here we carried out the electrical transport measurements of the air-stable RbCr3As3 after the dimensionality reduction. It is founded that the superconductivity is suppressed, while the upper critical field is still far larger than the Pauli paramagnetic limit, providing an ideal platform to shed light on the unconventional superconductivity.