New Non-Goldstone Collective Mode of BEC of Magnons in Superfluid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts><mml:mtext mathvariant="normal">−</mml:mtext><mml:mi mathvariant="normal">B</mml:mi></mml:math>

Človečko, M.; Gažo, E.; Kupka, Martin; Skyba, P.

doi:10.1103/physrevlett.100.155301

Cited by 18 publications

(16 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…If dissipation is small, the phase shift is small, α − α RF ≪ 1, and can be neglected. The neglected quadratic term (α − α RF ) 2 leads to the nonzero mass of the Goldstone boson -quantum of sound waves (phonon) in the magnon superfluid [21]; in 3 He-B the phonon mass, which is proportional to √ H RF , has been measured [22,23]. In the limit of small dissipation the main role of the RF field is to modify the profile of the GL free energy in (9) by adding the term:…”

mentioning

confidence: 99%

Magnon BEC in superfluid 3He-A

Bunkov

Volovik²

2009

Jetp Lett.

View full text Add to dashboard Cite

The new mode of magnetization precession in superfluid 3 He-A in a squeezed aerogel has been recently reported. We consider this mode in terms of the Bose-Einstein condensation (BEC) of magnons. The difference between magnon BEC states in 3 He-A and in 3 He-B is discussed. PACS:The discovery [1] and detailed investigations of the phase-coherent precession of magnetization in superfluid 3 He-B generated a search for similar phenomena in other systems. Superfluid 3 He-A could be a proper system. However, it was found that under typical conditions the coherent precession in 3 He-A is unstable [2] because of the convex shape of spin-orbit energy potential as function of magnetization [3,4]. It was suggested that the shape of potential can be inverted and thus the coherent precession can be stabilized if the orbital momentum of Cooper pairs in 3 He-A is oriented along the applied magnetic field [5]. Recently such orientation has been reached for 3 He-A immersed in the axially squeezed aerogel [6], and the first experiments with the coherently precessing state (CPS) of magnetization have been reported [7]. Here we discuss the phenomenon of the coherent precession of magnetization in superfluid 3 He-A in terms of the Bose-Einstein condensation (BEC) of magnons, and consider the difference between magnon BEC states in 3 He-A (CPS) and in 3 He-B (HPD). BEC is one of the most remarkable quantum phenomena. It corresponds to formation of collective quantum state, in which the macroscopic number of particles is governed by a single wave function. The formation of Bose-Einstein condensate was predicted by Einstein in 1925, for review see e.g. [8]. The almost perfect BEC state was observed in ultra could atomic gases. In Bose liquids, the BEC is strongly modified by interactions, but still remains the key mechanism for formation of coherent quantum state, which experiences the phenomenon of superfluidity: nondissipative superfluid current. In liquid 4 He the depletion of the condensate is very large: in the limit of zero temperature only about 10% of particles occupy the state with zero momentum. Nevertheless the whole liquid (100% of atoms) forms the 1) yuriy.bunkov@grenoble.cnrs.fr; volovik@boojum.hut.fi coherent quantum state at T = 0, so that the superfluid density equals the total density, ρ s (T = 0) = ρ. The latter is valid for any monoatomic superfluid system with translational invariance, including superfluid 3 He with the non BEC mechanism of coherent quantum state. If translational invariance is violated by impurities, crystal fields or other inhomogeneity, the superfluid component is suppressed:Superfluidity is a very general quantum property of matter at low temperatures, with variety of possible nondissipative superfluid currents, such as supercurrent of electric charge in superconductors; hypercharge supercurrent in the vacuum of Standard Model; supercurrent of color charge in a dense quark matter; etc. The origin of superfluidity is the spontaneous violation of the U (1) symmetry related to the conservation of ...

show abstract

mentioning

confidence: 99%

Magnon BEC in superfluid 3He-A

Bunkov

Volovik²

2009

Jetp Lett.

View full text Add to dashboard Cite

show abstract

“…, b q ; x) are the hypergeometric functions, ξ(t) is the size of the vortex core, R ρ (t) is the condensate size in radial direction (ρ), and R z (t) is the condensate size in axial direction (ẑ). The wave function (10) has integration domain defined by 1…”

Section: Equations Of Motionmentioning

confidence: 99%

“…The interest in this problem is motivated by the fact that these oscillations can be measured in the laboratory by moving the atomic cloud out of its equilibrium configuration by using the Feshbach resonance in order to modulate the scattering length [1][2][3][4][5]. These oscillations are also studied in other physical systems such as two-species condensates [6], BCS-BEC crossover [7][8][9], and superfluid Helium [10]. From the theoretical point of view, we are interested on how the size of the vortex core oscillates with respect to the external dimensions of the cloud.…”

Section: Introductionmentioning

confidence: 99%

Coupling vortex dynamics with collective excitations in Bose-Einstein condensates

Teles¹,

Bagnato²,

Santos³

2013

Phys. Rev. A

View full text Add to dashboard Cite

Here we analyze the collective excitations as well as the expansion of a trapped Bose-Einstein condensate with a vortex line at its center. To this end, we propose a variational method where the variational parameters have to be carefully chosen in order to produce reliable results. Our variational calculations agree with numerical simulations of the Gross-Pitaevskii equation. The system considered here turns out to exhibit four collective modes of which only three can be observed at a time depending of the trap anisotropy. We also demonstrate that these collective modes can be excited using well stablished experimental methods such as modulation of the s-wave scattering length.

show abstract

“…From a different point of view, the spontaneously formed coherent precession can be considered in the language of an out-of-equilibrium BoseEinstein condensate (BEC) of quasiparticles 15 , which for the case of 3 He-B are optical magnons. The spontaneous breaking of time translation symmetry leads to spin current Josephson effect, to quantized vortices in the magnon BEC and to the new NG mode -the propagating oscillations of the phase of precession [16][17][18][19][20][21][22][23] , which represents the usual phonon mode of the magnon BEC in the out-of-equilibrium BEC language 15 . In experiments, the out-of-equilibrium magnon BEC in superfluid 3 He arises when the system is either continuosly driven with an external transverse RF magnetic field H rf ⊥ H or after a short transverse RF field pulse is applied.…”

Section: Introductionmentioning

confidence: 99%

Effective Minkowski-to-Euclidean signature change of the magnon BEC pseudo-Goldstone mode in polar 3He

Nissinen

Volovik

2017

Jetp Lett.

View full text Add to dashboard Cite

We discuss the effective metric experienced by the Nambu-Goldstone mode propagating in the broken symmetry spin-superfluid state of coherent precession of magnetization. This collective mode represents the phonon in the RF driven or pulsed out-of-equilibrium Bose-Einstein condensate (BEC) of optical magnons. We derive the effective BEC free energy and consider the phonon spectrum when the spin superfluid BEC is formed in the anisotropic polar phase of superfluid 3 He, experimentally observed in uniaxial aerogel 3 He-samples. The coherent precession of magnetization experiences an instability at a critical value of the tilting angle of external magnetic field with respect to the anisotropy axis. From the action of quadratic deviations around equilibrium, this instability is interpreted as a Minkowski-to-Euclidean signature change of the effective phonon metric. We also note the similarity between the magnon BEC in the unstable region and an effective vacuum scalar "ghost" condensate.

show abstract

New Non-Goldstone Collective Mode of BEC of Magnons in SuperfluidHe3−B

Cited by 18 publications

References 12 publications

Magnon BEC in superfluid 3He-A

Magnon BEC in superfluid 3He-A

Coupling vortex dynamics with collective excitations in Bose-Einstein condensates

Effective Minkowski-to-Euclidean signature change of the magnon BEC pseudo-Goldstone mode in polar 3He

Contact Info

Product

Resources

About