Bunkov Yu M, Kuzmichev A N, Safin T R, Vetoshko P M, Belotelov V I, Tagirov M S
M-Granat, Russian Quantum Center, Bolshoy Bulvar, 42, Skolkovo, Moscow, Russia, 121205.
Kazan Federal University, Kazan, Russia, 420008.
Sci Rep. 2021 Apr 7;11(1):7673. doi: 10.1038/s41598-021-87196-w.
The explosive development of quantum magnonics requires the consideration of several previously known effects from a new angle. In particular, taking into account the quantum behavior of magnons is essential at high excitations of the magnetic system, under the conditions of the so-called phenomenon of "foldover" (bi-stable) magnetic resonance. Previously, this effect was considered in the quasi-classical macrospin approximation. However, at large angles of magnetization precession, the magnon density exceeds the critical value for the formation of a magnon Bose condensate (mBEC). Naturally, this purely quantum phenomenon does not exist in the classical approximation. In addition, mBEC leads to superfluid transfer of magnetization, which suppresses the macroinhomogeneity of the samples. The experiments presented in the article show that quantum phenomena well describes the experimental results of nonlinear magnetic resonance in yttrium iron garnet. Thus, we remove the questions that arose earlier when considering this effect without taking into account quantum phenomena. This discovery paves the way for many quantum applications of supermagnonics, such as the magnetic Josephson effect, long-range spin transport, Q-bits, quantum logic, magnetic sensors, and others.
量子磁振子学的迅猛发展需要从新的角度考虑几个先前已知的效应。特别是，在磁系统的高激发下，即在所谓的“折叠”（双稳态）磁共振现象的条件下，考虑磁振子的量子行为至关重要。以前，这种效应是在准经典宏观自旋近似中考虑的。然而，在大的磁化进动角度下，磁振子密度超过了形成磁振子玻色凝聚（mBEC）的临界值。自然地，这种纯粹的量子现象在经典近似中并不存在。此外，mBEC导致磁化的超流体转移，这抑制了样品的宏观不均匀性。文章中展示的实验表明，量子现象很好地描述了钇铁石榴石中非线性磁共振的实验结果。因此，我们消除了早期在不考虑量子现象的情况下考虑这种效应时出现的问题。这一发现为超磁振子学的许多量子应用铺平了道路，如磁约瑟夫森效应、长程自旋输运、量子比特、量子逻辑、磁传感器等。
