Superconducting tungsten-rhenium films: A potential candidate for single photon detectors and quantum devices

Title : Superconducting tungsten-rhenium films: A potential candidate for single photon detectors and quantum devices

Abstract:

Recent measurements were done on superconducting tungsten rhenium (WRe) and nitrogen-doped WRe (WReN) films, which show their potential capability for superconducting single photon detectors (SSPDs) and quantum devices. The films were deposited by using DC magnetron sputtering technique. The structural characterization (X-ray diffraction, XRD) shows crystalline nature for WRe and nearly amorphous features for WReN along with disorderness. The WRe films exhibit superconductivity at transition temperature, T_c- 5 K, lower than WReN (T_c-6 K). For films, the zero-temperature upper critical fields, H_c2(0) are in the range of 5-8 T, while coherence lengths have the values in the range of 6-8 nm. The analysed relaxations times, which are essential to know for a SSPDs because they effect the response time, detection efficiency, jitter time and dark count rate, are of the order of picosecond allowing to show fast response of WRe-based films. Furthermore, an extracted high ratio of times in electron- phonon to electron-electron scattering belongs to larger hotspot area and improved detection efficiency of WRe and WReN films. These parameters further compared with well-known SSPDs materials- NbN, NbTiN, WSi, WGe, revealing potential applicability of WRe and WReN films in SSPDs. Along with this WRe and WReN show quantum phase transitions (quantum Griffith singularity- like nature), which is being analysed within the framework of quantum and superconducting fluctuations. The existence of these novel phenomena is reliable for the applicability of WRe and WReN films for quantum circuits and quantum devices.

Biography:

Abhishek Kumar completed his PhD at CSIR–National Physical Laboratory, India, in the field of superconductivity. During PhD, his research work focused on the fabrication of superconducting tungsten devices, including films, nanowires, and junctions, which exhibited several novel phenomena such as quantum and thermally activated phase slips, proximity effects with multiple Andreev reflections, and laser light-dependent photoresponse features. These properties make them promising candidates for applications in quantum metrology, superconducting and quantum devices, SNSPDs, and optoelectronic devices. Currently, he is working as a postdoctoral fellow at the University of Salerno, Italy. His present research interests include exploring tungsten–rhenium and niobium–rhenium films for SSPDs, as well as applications in spintronics, superconducting, and quantum devices.