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Chen, A. S.; Bunkov, Yuri M.; Godfrin, H.; Schanen, R.; Scheffler, Falk

doi:10.1023/a:1022554415394

Cited by 8 publications

(5 citation statements)

References 6 publications

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“…The size of the Q-ball grows with Q, and the frequency starts to decrease. This behavior is in agreement with the observation that the Persistent Signal starts to grow from the linear spin wave localized in the texture [12,13]. During the downward frequency sweep, the spin wave frequency is trapped by the rf field and after that the amplitude of the signal grows significantly (Fig.…”

supporting

confidence: 91%

“…These are not the only possible Q-balls. In the Grenoble experiments [12] the formation of many different Q-balls have been observed. They are generated by spin waves in the broad range of frequencies.…”

Section: Figmentioning

confidence: 99%

“…For small β one has M 2 ⊥ ∼ r 2 Q l Q SQ ∼ ξ D l Q S/κ, which gives the frequency shift of the Q-ball as a function of the transverse magnetization: Fig.1 shows the formation of Q-balls generated by several spin wave modes. The signals were recorded at a temperature T = 0.22T c , pressure 29 bar and different amplitudes of the rf field (for details, see [12]). By applying different gradients of magnetic field we are able to localize the positions of the Q-balls.…”

mentioning

confidence: 99%

“…2 the experimental results for the Q-balls A and B are compared with the theoretical estimations in Eqs. (12) and (13). The solid line corresponds to Eq.…”

mentioning

confidence: 99%

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Magnon Condensation into aQBall inHe3−B

Bunkov

Volovik

2007

Phys. Rev. Lett.

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The theoretical prediction of Q-balls in relativistic quantum fields is realized here experimentally in superfluid 3 He-B. The condensed-matter analogs of relativistic Q-balls are responsible for an extremely long lived signal of magnetic induction -the so-called Persistent Signal -observed in NMR at the lowest temperatures. This Q-ball is another representative of a state with phase coherent precession of nuclear spins in 3 He-B, similar to the well known Homogeneously Precessing Domain which we interpret as Bose condensation of spin waves -magnons. At large charge Q, the effect of self-localization is observed. In the language of relativistic quantum fields it is caused by interaction between the charged and neutral fields, where the neutral field provides the potential for the charged one. In the process of self-localization the charged field modifies locally the neutral field so that the potential well is formed in which the charge Q is condensed.PACS numbers: 67.57. Fg, 05.45.Yv, 11.27.+d Keywords: non-topological soliton, Q-ball, spin superfluidity A Q-ball is a non-topological soliton solution in field theories containing a complex scalar field φ. Q-balls are stabilized due to the conservation of the global U (1) charge Q [1]: they exist if the energy minimum develops at nonzero φ at fixed Q. At the quantum level, Q-ball is formed due to suitable attractive interaction that binds the quanta of φ-field into a large compact object. In some modern SUSY scenarios Q-balls are considered as a heavy particle-like objects, with Q being the baryon and/or lepton number. For many conceivable alternatives, Q-balls may contribute significantly to the dark matter and baryon contents of the Universe, as described in review [2]. Stable cosmological Q-balls can be searched for in existing and planned experiments [3].The Q-ball is a rather general physical object, which in principle can be formed in condensed matter systems. In particular, Q-balls were suggested in the atomic BoseEinstein condensates [4]. Here we report the observation of Q-balls in NMR experiments in superfluid 3 He-B, where the Q-balls are formed as special states of phase coherent precession of magnetization. The role of the Qcharge is played by the projection of the total spin of the system on the axis of magnetic field, which is a rather well conserved quantity at low temperature. At the quantum level, this Q-ball is a compact object formed by magnons -quanta of the corresponding φ-field. Two types of coherent precession of magnetization have been observed in in superfluid3 He-B. The first state known as the Homogeneously Precessing Domain (HPD) was discovered in 1984 [5]. This is the bulk state of precessing magnetization which exhibits all the properties of spin superfluidity and Bose condensation of magnons (see Reviews [6,7]). These include in particular: spin supercurrent which transports the magnetization (analog of the mass current in superfluids and electric supercurrent in superconductors); spin current Josephson effect and phase-slip process...

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supporting

confidence: 91%

Section: Figmentioning

confidence: 99%

mentioning

confidence: 99%

“…2 the experimental results for the Q-balls A and B are compared with the theoretical estimations in Eqs. (12) and (13). The solid line corresponds to Eq.…”

mentioning

confidence: 99%

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Magnon Condensation into aQBall inHe3−B

Bunkov

Volovik

2007

Phys. Rev. Lett.

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“…5 shows numerical simulations of the spatial distribution of magnon density inside thel texture for different Q in one dimensional case. Note another feature of Qballs: with increasing number Q of the trapped magnons the potential well itself becomes modified by magnons and finally it is overwhelmingly determined by Q. Simultanious formation of many different Q-balls has been observed in CW NMR 25 . They are generated by spin waves in the broad range of frequencies.…”

Section: Magnon Condensation Into Q-ballmentioning

confidence: 97%

Bose-Einstein Condensation of Magnons in Superfluid 3He

Bunkov

Volovik

2007

J Low Temp Phys

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The possibility of Bose-Einstein condensation of excitations has been discussed for a long time. The phenomenon of the phase-coherent precession of magnetization in superfluid 3 He and the related effects of spin superfluidity are based on the true Bose-Einstein condensation of magnons. Several different states of coherent precession has been observed in 3 He-B: homogeneously precessing domain (HPD); persistent signal formed by Q-balls at very low temperatures; coherent precession with fractional magnetization; and two new modes of the coherent precession in compressed aerogel. In compressed aerogel the coherent precession has been also found in 3 He-A. Here we demonstrate that all these cases are examples of a Bose-Einstein condensation of magnons, with the magnon interaction term in the Gross-Pitaevskii equation being provided by different types of spin-orbit coupling in the background of the coherent precession.

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Spin-Orbital Dynamics in the B-Phase of Superfluid Helium-3

Bunkov

Golo

2004

Journal of Low Temperature Physics

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Cited by 8 publications

References 6 publications

Magnon Condensation into aQBall inHe3−B

Magnon Condensation into aQBall inHe3−B

Bose-Einstein Condensation of Magnons in Superfluid 3He

Spin-Orbital Dynamics in the B-Phase of Superfluid Helium-3

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