Abstract
We suggest a new type of an ultrasensitive detector of electromagnetic fields exploiting the giant thermoelectric effect recently found in superconductor/ferromagnet hybrid structures. Compared to other types of superconducting detectors where the detected signal is based on variations of the detector impedance, the thermoelectric detector has the advantage of requiring no external driving fields. This becomes especially relevant in multi-pixel detectors where the number of bias lines and the heating induced by them becomes an issue. We propose different material combinations to implement the detector and provide a detailed analysis of its sensitivity and speed. In particular, we perform to our knowledge the first proper noise analysis that includes the cross correlation between heat and charge current noise and thereby describes also thermoelectric detectors with a large thermoelectric figure of merit.
Highlights
Some of the most accurate sensors of wideband electromagnetic radiation are based on superconducting films
At high temperatures, where such thermoelectric effects would be strong enough, the thermal noise hampers the device sensitivity. We suggest overcoming these problems in a superconductor-ferromagnet thermoelectric detector (SFTED) [18] by exploiting the newly discovered giant thermoelectric effect that occurs in superconductor
Most of the previously studied thermoelectric detectors have relied on using semiconducting thermoelectric materials, operating at and above room temperature TRT
Summary
Some of the most accurate sensors of wideband electromagnetic radiation are based on superconducting films. Ferromagnet heterostructures [19,20,21,22] for radiation sensing As this thermoelectric effect can be realized with close to Carnot efficiency [19,22] even at subkelvin temperatures, the resulting detector can have a large signal-to-noise ratio, and a noise-equivalent power (NEP) rivaling those of the best TESs and KIDs without the burden of having to use additional bias lines for probing the sensor, and with zero (for ideal amplification) or at most very small nonsignal power dissipation at the sensor location. The sensor element (i.e., one pixel of a possible detector array) is formed from a thin-film superconductor–ferromagnetic insulator bilayer coupled to superconducting antennas via a clean (Andreev) contact This bilayer is further connected, via a tunnel junction (magnetic or normal) to a ferromagnetic electrode [24].
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