#	Pagina
attuale pagina	/open-h2020/projects/216307/results.html

Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SUPERTED (Thermoelectric detector based on superconductor-ferromagnet heterostructures)

Teaser

Summary

Superconducting detectors, such as the transition edge sensor and the kinetic inductance detector, are some of the most sensitive detectors of electromagnetic radiation and they have found application in various fields ranging from astrophysical observations to security imaging and materials characterization. The present tendency is to increase the number of sensor pixels to allow for a simultaneous imaging and spectroscopy in the video rate of the measured object. However, increasing the number of pixels is hampered by the technical difficulty of fabricating and controlling the bias lines needed next to each pixel in these types of sensors, along with the heating problem associated with them. In this project, we propose to study a new type of sensor that overcomes this limitation as it is based on the thermoelectric conversion of the radiation signal to electrically measurable one. This approach is based on the newly found giant thermoelectric effect taking place in superconductor/ferromagnet heterostructures. Utilizing this effect, the sensor pixels can be self-powered by the measured radiation, and therefore extra bias lines are not needed (patent pending for the detector concept). Within the project, we aim to establish a proof of concept of this device by (i) fabricating such detector elements, and (ii) characterizing single pixels of thermoelectric detectors for X-ray and THz imaging via approaches that are scalable to large arrays. Within the project, we also actively seek to establish technology transfer to pave the way for the possible commercial application of such sensors.

Work performed

During the first year we have successfully started a process to grow and characterize EuS/Al multilayers in CSIC. These multilayers were shown to exhibit both superconducting and magnetic properties in the measurements in CNR. In addition, the CNR partner has measured samples received from our colleague in MIT, showing both a spin-split superconducting state and tunneling with spin filtering. These measurements guide us in finding the optimal parameters for the detector samples and help in planning the detector read-out. We have also studied the possibility of reading out the detectors with SQUID amplifiers. Our theoretical analysis shows that the TED X-ray detectors may outperform the present-day transition edge sensors both in sensitivity and speed.

The work has been published in 10 scientific papers, 4 of them in journals with an impact factor larger than 7. In addition, we have told about SUPERTED in various events and press releases.

Final results

The first EuS/Al samples grown in CSIC showed no superconductivity. Performing as control measurements the first ever spin Hall measurements in EuS/Pt samples showed a way to estimate the size of the exchange field even in the absence of superconductivity. These measurements indicated the reason for the lack of superconductivity, coming from the too ideal contact between the magnetic EuS and superconducting Al: the induced exchange field drives the superconductor into the normal state.

We have followed our project proposal very carefully. During the next reporting period we expect to demonstrate the world\'s first superconducting thermoelectric detection of electromagnetic radiation. After that we will optimize the detectors and aim at proving their benefits compared to the present-day superconducting detectors. If successful, this progress may open the way to widen the use of superconducting detectors to new regimes of imaging. Such advances are important in a wide range of applications, ranging from astrophysical and security imaging to elemental analysis of materials and bioimaging.