Thermodynamics of magnon gases and Bose-Einstein condensation driven by pure spin currents
Final Report Abstract
This project is devoted to the experimental study of the thermodynamic characteristics of magnon gases and magnon kinetics in different systems driven by pure spin currents. The main goals of the project are to understand in detail physical processes in magnon gases under the influence of pure spin current, to develop approaches enabling the observation of current-driven roomtemperature Bose-Einstein condensates (BEC) of magnons, to study the characteristics of such condensates and to find mechanisms that enable their control and manipulation. In the course of the project implementation we were able to identify the physical mechanisms responsible for the instability of the quasi-equilibrium state of the current-driven magnon gas. In particular, we have shown that the main factor responsible for the instability is the strong attractive magnon-magnon interaction in current-driven systems. We have elaborated an approach, which allowed us to minimize this interaction and have shown that it enables the formation of stable spatially extended BEC driven by pure spin currents. The observed condensates are characterized by high temporal and spatial coherence and are stable in a broad range of the densities of the magnon gas. Our findings open new avenues for the studies of magnon BEC by demonstrating an approach enabling creation of magnon BEC without breaking the equilibrium between lowenergy and high-energy magnons. The simple and robust driving method based on the utilization of the spin-Hall effect at the micrometer scale enables implementation of a large variety of new experiments.
Publications
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Controllable excitation of quasi-linear and bullet modes in a spin-Hall nano-oscillator. Applied Physics Letters, 114(4).
Divinskiy, B.; Demidov, V. E.; Urazhdin, S.; Freeman, R.; Rinkevich, A. B. & Demokritov, S. O.
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Excitation of coherent second sound waves in a dense magnon gas. Scientific Reports, 9(1).
Tiberkevich, V.; Borisenko, I. V.; Nowik-Boltyk, P.; Demidov, V. E.; Rinkevich, A. B.; Demokritov, S. O. & Slavin, A. N.
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Magnon Laser. Ukrainian Journal of Physics, 64(10), 938.
Nowik-Boltyk, P.; Borisenko, I. V.; Demidov, V. E. & Demokritov, S. O.
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Brillouin light scattering of spin waves inaccessible with free-space light. Physical Review Research, 2(3).
Freeman, Ryan; Lemasters, Robert; Kalejaiye, Tomi; Wang, Feng; Chen, Guanxiong; Ding, Jinjun; Wu, Mingzhong; Demidov, Vladislav E.; Demokritov, Sergej O.; Harutyunyan, Hayk & Urazhdin, Sergei
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Direct evidence of spatial stability of Bose-Einstein condensate of magnons. Nature Communications, 11(1).
Borisenko, I. V.; Divinskiy, B.; Demidov, V. E.; Li, G.; Nattermann, T.; Pokrovsky, V. L. & Demokritov, S. O.
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Spatial separation of degenerate components of magnon Bose–Einstein condensate by using a local acceleration potential. Scientific Reports, 10(1).
Borisenko, I. V.; Demidov, V. E.; Pokrovsky, V. L. & Demokritov, S. O.
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Evidence for spin current driven Bose-Einstein condensation of magnons. Nature Communications, 12(1).
Divinskiy, B.; Merbouche, H.; Demidov, V. E.; Nikolaev, K. O.; Soumah, L.; Gouéré, D.; Lebrun, R.; Cros, V.; Youssef, Jamal Ben; Bortolotti, P.; Anane, A. & Demokritov, S. O.
