Polarity-Switchable Sensitive Photodetection in a Superconducting van der Waals Heterostructure

The exploration of switchable photoconductivity, alternating between positive and negative responses, has been conducted across various materials and systems, presenting numerous potential applications, including optical logic gates, quantum computing, and optoelectronic integration. Nevertheless, many existing polarity-tunable photodetectors struggle with low responsivity or a restricted spectral range, limiting effective information processing, storage, and energy transfer efficiency. In this research, we introduce a superconducting photodetector constructed from a NbSe₂-WTe₂-NbSe₂ van der Waals heterostructure, which demonstrates a highly sensitive and adjustable photoresponse spanning the visible to near-infrared spectrum. In the high bias voltage range, we observe a conventional negative photoresponse, attributed to the photoinduced superconducting phase transition of NbSe₂. Conversely, in the low bias voltage regime, we detect an unusual positive photoconductivity associated with light-modulated Andreev reflection at the superconducting interface. Both types of photoresponsivity surpass 0.3 A/W (0.35 A/W for positive and -5 A/W for negative photocurrent signals), and the polarity of photoconductivity can be toggled by precisely adjusting the bias voltage, excitation light power, or temperature. Our results provide fresh insights into the physical mechanisms behind superconducting photodetectors influenced by quantum effects, with significant implications for the development of optoelectronic devices in information processing.