Thermoelectric Radiation Detector Based on Superconductor-Ferromagnet Systems

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. PACS numbers:arXiv:1709.08856v3 [cond-mat.supr-con]

Thermalization of hot electrons via interfacial electron-magnon interaction

“…where Σ is the material dependent electron-phonon coupling constant, Ω is the volume of the film, N σ (E) = N S (E + σh) where σ = ±1 for σ =↑ / ↓, and ζ(5) is the Riemann zeta function. The analytical estimate of the bulk value of G q−ph is [8,16] 17), we note that the electron-magnon thermalization process can dominate the electron-phonon process at low temperatures, whereas electron-phonon is the dominating mechanism at high temperatures. As a result there can be a crossover temperature, where both heat conductances are equal to each other.…”

“…1, based on a thin-film normal metal (N) or a thin-film superconductor (S) in contact with a thin-film ferromagnetic insulator (FI). It can be a part of some low-temperature thermometric device, such as a thermoelectric radiation detector (TED) [8,9]. When such devices are operated, they are often brought out of equilibrium via a process involving absorption of an electromagnetic field with power P γ .…”

Thermal, electric and spin transport in superconductor/ferromagnetic-insulator structures

“…The self-energies are defined in Eqs. (33) and (34). In the superconducting state, the form of the spin-flip and spin-orbit contributions to the collision integrals differ due to their different properties under time reversal.…”

“…Even though spectral properties of S/FI have been intensively studied for a long time, only recently it has been realized that spin-split superconductors may find applications in spintronics, thermoelectricity, and sensors [3,28,29,30,31,32,33,34]. To understand the physics underlying these applications one needs to consider nonequilibrium phenomena.…”

Nonlocal thermoelectric effects in high-field superconductor-ferromagnet hybrid structures

“…Recently, large spin-dependent thermoelectric effects have been predicted [5,6] and observed [7][8][9] in high-field superconductor-ferromagnet tunnel junctions. These thermoelectric effects are predicted to lead to exceptional thermoelectric figures of merit ZT ∼ 40 in optimized structures [10], and can be potentially applied in high-resolution thermometers [11], radiation detectors [12] and coolers [13]. Spin-dependent thermoelectric effects in these structures are linked to coupled long-range spin and heat transport [14][15][16][17], which can be driven either by voltage or thermal bias [5].…”