Yury Bunkov

Yury 'Mikhailovich Bunkov' is a Russian experimental physicist, specializing in condensed matter physics. He is known as one of the co-discoverers of the quantum spin liquid state.

Education and career

Bunkov, born into a family of geologists, graduated in 1968 from a special school for physics and mathematics in Moscow. In 1968 he also achieved first place in the Moscow Physics Olympiad and matriculated at the Moscow Institute of Physics and Technology, which was headed by Piotr Kapitza.
According to Bunkov, the "parametric echo" should be called the "Bunkov echo":
In 1974 he matriculated at the Kapitza Institute for Physical Problems, where he received in 1979 his Candidate of Sciences degree. A. S. Borovik-Romanov was Bunkov's thesis advisor. At the Kapitza Institute for Physical Problems, he was employed as a non-principal scientist from 1979 to 1985, a principal scientist from 1985 to 1986, and from 1986 to 1995 as a leading scientist. At the Kapitza Institute he constructed the Soviet Union's first nuclear demagnetization refrigerator.
In 1983 at the Kapitza Institute, quantum spin superfluidity was discovered by Bunkov, who was the team leader, with Vladimir Dmitriev and Yuri Mukharsky. Spin superfluidity manifested itself in NMR studies on ³helium-B as regions of coherent Larmor precession, with inhomogeneities in the precession caused by supercurrents in the spin similar to those in superconductivity and superliquid or Bose-Einstein condensates. Spin superfluidity is also a Bose-Einstein condensate of magnons. A theoretical explanation was given in the 1980s by the theorist Igor Akindinovich Fomin.
Bunkov wrote concerning his work at the Kapitza Institute:
At the Kapitza Institute, he received in 1985 his Russian Doctor of Sciences degree with a thesis on NMR studies on superfluid helium-3. At Grenoble's Institut Néel, belonging to the Centre National de la Recherche Scientifique (CNRS), he was employed from 1995 to 2004 as a Directeur de Recherche and since 2004 is employed as a Directeur de Recherche de 1^er classe. From 2008 to the present, he is a part-time professor at Kazan Federal University.
For many years Bunkov participated in the Soviet-Finnish project ROTA, in which the researchers discovered many different types of ³He vortices. He also made many visits to Lancaster University, where he participated in NMR experiments at record-setting low temperatures for ³He.
At CRTBT his research group cooled ³He to 100 K and, at such low temperatures, found in 1996 an energy deficit after a ³He neutron capture reaction. The energy deficit "appeared to arise from vortex creation via the Kibble-Zurek cosmological mechanism, in analogy with cosmic-string creation in the early Universe." He became the leader of the project ULTIMA, which has as its purpose the development of a dark-matter detector based on overcooled superfluid ³He.
In the ³He-B phase he experimentally discovered analogues to cosmological and quantum field theoretical phenomena, such as cosmological strings and Majorana quasiparticles. In the 1980s he and his colleagues detected Goldstone modes. In the 2000s he discovered Q-balls] in superfluid ³He.
He collaborated extensively with the theorist Grigori Efimovich Volovik. In 2008, Bunkov and his Japanese colleagues discovered coherent precession in the helium-3-A phase embedded in uniaxially deformed anisotropic aerogels.
Bunkov is internationally recognized for his research on quantum fluids and solids, superfluid ³He nuclear magnetic resonance

Selected publications

with A.S. Borovik-Romanov, V.V. Dmitriev, Yu.M. Mukharskiĭ: Long-lived induction signal in superfluid in ³-He, JETP Lett., vol. 40, no. 6, 1984, pp. 1033–1037
with V.V. Dmitriev, Yu.M. Mukharskiy: Twist oscillations of homogeneous precession domain in ³He-B, JETP Lett., vol. 43, 1986, pp. 168–171.
with A. S. Borovik-Romanov:, Harwood Academic Publ. 1990.
with V.V.Dmitriev, Yu.M. Mukharskiy, Low frequency oscillations of the homogeneously precessing domain in ³He-B, Physica B, vol. 178, 1992, pp. 196–201.
Persistent signal; coherent NMR state trapped by orbital texture, J. Low Temp. Phys., vol. 138, 2005, pp. 753–758,
with G.E. Volovik: Magnon condensation into a Q-ball in ³He-B, Phys. Rev. Lett., vol. 98, 2007, p. 265302.
Spin Supercurrent, J. of Magnetism and Magnetic Materials.
with T. Sato, T. Kunimatsu, K. Izumina, A. Matsubara, M. Kubota, T. Mizusaki: Coherent precession of magnetization in the superfluid ³He A-phase, Phys. Rev. Lett., vol. 101, 2008, p. 055301.
with G. E. Volovik: Bose-Einstein Condensation of Magnons in Superfluid ³He, J. Low Temperature Physics, vol. 150, 2008, pp. 135–144.
with G.E. Volovik: Magnon BEC in superfluid ³He-A, JETP Lett., vol. 89, 2009, pp. 306–310.
with G. E. Volovik: Magnon BEC and spin superfluidity: a ³He primer,
Spin superfluidity and magnons Bose-Einstein-Condensation, Physics Uspekhi, August 2010,
with G. E. Volovik: Spin superfluidity and magnon BEC, in: Int. Ser. Monogr. Phys. 156, 2013, pp. 253–311,
with Rasul Gazizuzin: Observation of Majorana Quasiparticles Surface States in Superfluid ³He-B by Heat Capacity Measurements,
with Vladimir Safonov: Magnon Condensation and Spin Superfluidity,
with A. Farhutdinov. A. Kuzmichev, T. R. Safin, P. M. Vetoshko, V. I. Belotelov. and V. I. Tagirov: The magnonic superfluid droplet at room temperature. arXiv preprint arXiv:1911.03708
Magnonic Superfluidity Versus Bose Condensation, Appl. Magn. Reson. vol. 51, 2020, pp. 1711–1721.
with A. N. Kuzmichev, T. R. Safin, P. M. Vetoshko, V. I. Belotelov, and M. S. Tagirov: Quantum paradigm of the foldover magnetic resonance, Scientific Reports, vol. 11, no. 1, 2021, pp. 1–8.