Abstract
The adaptation of systems to external influences is of broad interest. We study the influence of microwave signals of different shapes on the magnetoacoustic wave system with a giant nonlinearity in canted antiferromagnet FeBO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> at room temperature, which is close to its phase transition to the paramagnetic state. The classical nonlinear system obeys external deterministic signals; the modulation response describes the shape of these signals. In response to a noisy spectrum, the system shows self-organization, and mode competition selects one excited mode while suppressing others. With an increase in the power of the external signal, another self-organization is observed in the form of a narrow peak at the frequency of the fundamental minimum. This represents the first observation of the macroscopic quantum statistical phenomenon, Bose-Einstein condensation of magnetoacoustic wave quanta in a wave system with a high level of thermal fluctuations. The resulting picture of adaptation can analogously be transferred to many other adaptive wave systems, including large scale adaptive wave systems in the natural environment.
Highlights
Adaptive systems encompass phenomena across many diverse environments and a wide range of sciences [1]–[3]
We study the adaptation of a system of magnetoacoustic waves (MAWs) in antiferromagnetic iron borate (FeBO3) to external alternating magnetic fields as an extremely convenient and simple model with mathematical analogies in many other nonlinear wave systems
Where cs is the sound velocity, H describes the efficiency of linear interaction between magnetic and acoustic subsystems, ωsw,k ≈ γ [Hs (Hs + HDM ) + H 2 +2]1/2 is the frequency of the spin wave, Hs is the static magnetic field, HDM is the Dzyaloshinskiı-Moriya field, and α is the non-uniform exchange constant
Summary
Adaptive systems encompass phenomena across many diverse environments and a wide range of sciences [1]–[3]. Safonov et al.: Adaptation of Fluctuating Magnetoacoustic System to External Signals system self-organized leading to competition of modes and the excitation of only one mode. All these phenomena can be described within the framework of the classical wave formalism [6], [7]. We found that weak wave turbulence leads to energy flux down the spectrum and excitation of coherent vibrations at the lowest eigenfrequency of the sample This is a quantum statistical effect known as quasi-equilibrium Bose-Einstein condensation (BEC) of MAW quanta at the fundamental minimum of the spectrum. We show that a macroscopic quantum phenomenon is observed in a system that appears to be classical in terms of both the excitation level and fluctuations
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