Condensed Matter Physics Seminar: Tuneable receiver of sub-THz signals based on an antiferromagnet
Dr. Andrei Slavin, Oakland University
Abstract: Antiferromagnetic (AFM) materials have natural resonance frequencies in the sub-THz or THz frequency range. Thus, it is tempting to use antiferromagnets (AFM) as active layers in THz-frequency detectors. Recently [1], it has been shown theoretically that a dielectric AFM having bi-axial anisotropy, such as NiO, can be used for the resonance quadratic rectification of a linearly polarized AC spin current of THz frequency, and could have a sensitivity in the range of 100–1000 V/W.
We present analytical and numerical data illustrating the performance of a possible electrically tunable resonance THz-frequency receiver based on an AFM crystal having the frequency of the antiferromagnetic resonance (AFMR) in the THz-frequency range [2]. The receiver is based on a layered structure consisting of a layer of a uniaxial AFM crystal and two layers of a heavy metal (HM). The conversion of the received AC signal into an output DC signal is done using the inverse spin Hall effect in the (AFM/HM) bilayer. An additional bias DC current in the bottom HM layer can be used for the tuning of the AFMR frequency of the system, and for a partial regeneration of the system losses. The AFMR frequency can be continuously tuned in a substantial frequency interval (of about 0.5 THz) by varying the magnitude of the DC electric current. It is shown that the AC sensitivity of the proposed AFM/HM-based detector is comparable to the sensitivity of the modern sub-millimeter-wave detectors based on the Schottky and Gunn diodes, and that the received DC signals are well above the level of the thermal noise for the AC signals having power of the order of several microwatts.
_________________________________________________________________
[1] R. Khymyn et al., AIP Adv. 7, 055931 (2017)
[2] A. Safin et al., Appl. Phys. Lett. 117, 222411 (2020).
Andrei Slavin received PhD degree in Physics in 1977 from the St. Petersburg Technical University, St. Petersburg, Russia. Dr. Slavin developed a state-of-the-art theory of spin-torque oscillators, which has numerous applications in the theory of current-driven magnetization dynamics in magnetic nanostructures. His current research support includes multiple grants from the U.S. Army, DARPA, SRC and the National Science Foundation. This research involves international collaborations with leading scientists in many countries, including Germany, Ukraine, France, Italy, and the United States. Dr. Slavin is a frequently invited speaker at magnetism conferences around the world. Andrei Slavin is Fellow of the American Physical Society, Fellow of the IEEE, and Distinguished Professor and Chair of the Physics Department at the Oakland University, Rochester, Michigan, USA.