Low-Detectable-Power Cooled Terahertz-Frequency Signal Detector Based on an Antiferromagnetic Tunnel Junction

In this paper, we present a theoretical proposal of a terahertz-frequency signal detector based on the $\mathrm{Pt} / \mathrm{Ir}_{0.2} \mathrm{Mn}_{0.8} / \mathrm{MgO} / \mathrm{Pt}$ antiferromagnetic tunnel junction (ATJ), which can exhibit a sufficiently high signal-to-noise ratio and low detectable input ac power at cryogenic temperatures. The detector is an active device employing a dc current-driven terahertz-frequency oscillations of the junction tunneling anisotropic magnetoresistance (TAMR). When an external ac signal current is applied to the junction, the detector output de voltage is generated when the frequency of the current-driven TAMR oscillations and the input ac signal frequency are equal. Here, we extend our previously developed temperature-dependent model of an ATJ-based signal detector by choosing the better impedance matching condition between the detector and an external electrodynamic system and by considering a stronger temperature dependence of the TAMR. We numerically calculate the output dc voltage, the signal-to-noise ratio, and the minimum detectable ac power for the detector operating in the presence of low-frequency Johnson-Nyquist thermal noise, and find that the minimum detectable ac power can drop to about 10 pW or less at liquid helium temperature (4.2 K) and to about 20 pW or less at 77 K for a detector operating at some “optimal” frequency $\sim 0.2 \mathrm{THz}$. The obtained results can be useful for the development and optimization of terahertz signal detectors based on antiferromagnetic spintronic nanostructures.