Resonance absorption of microwaves in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>He</mml:mi><mml:mspace width="0.3em" /><mml:mi>II</mml:mi></mml:mrow></mml:math>: Evidence for roton emission

Rybalko, A. S.; Rubets, S. P.; Rudavskiı̆, É. Ya.; Tikhiy, V. A.; Tarapov, S. I.; Golovashchenko, R. V.; Деркач, В. Н.

doi:10.1103/physrevb.76.140503

Cited by 58 publications

(73 citation statements)

References 16 publications

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“…Let the line width be the distance between the points, which located on both sides from the line center, and for which the intensity of a signal is about 0.8 of the background one (the signal far from the line). Then it follows from the experiment [1,2] that the line width is about 50 kHz at T = 1.8 K and decreases, at lower T, to the resolving power of a spectroscope (≃ 30 kHz). Moreover, the width stops to decrease at T < ∼ 1.6 K and approaches a constant ≃ 30 kHz.…”

Section: Width Of the Roton Absorption Linementioning

confidence: 92%

“…. dR (1) N dR (2) N are the phase volumes of all nuclei and all electrons, Ψ i and Ψ f are the wave functions (WFs) of the initial and final states of helium, respectively, E f − E (0) i = E c is the energy of a c-phonon, and ω = 2πν. The explicit formula forF follows from the perturbation operator…”

Section: Probability Of the Creation Of A Circular Phonon By The mentioning

confidence: 99%

“…We now evaluate these contributions quantitatively for the roton line and conditions of the experiment [1,2]. According to [3], the relation J l−1 (Q 1 R d ) ≈ 1/27.831 is valid at l = l rot = 66.…”

Section: ∂ ∂R1mentioning

confidence: 99%

“…In the recent works [1,2], an unconventional effect was discovered. In a dielectric disk-shaped resonator placed in liquid 4 He, the azimuth (l-)modes were excited.…”

mentioning

confidence: 99%

“…It is necessary to take into account that the EM field of a disk-shaped resonator has the circular (c-) symmetry and is concentrated only near the disk according to measurements [1] and the theory [3]. Since namely the EM field induces the transition, the latter must be characterized by the c-symmetry.…”

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confidence: 99%

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Theory of a supernarrow roton absorption line in the spectrum of a disk-shaped microwave resonator

Локтев

Tomchenko

2010

Phys. Rev. B

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We calculate the probability of the creation of a circular phonon (c-phonon) in He II by a cphoton of the resonator. It is shown that this probability has sharp maxima at frequencies, where the effective group velocity of the c-phonon is equal to zero; the density of states of c-phonons strongly grows at such frequencies. For He II, these frequencies correspond to a roton and a maxon. From the probability of the c-roton creation, we calculate the roton line width which is found to approximately agree with the experimental one. We conclude that the roton line observed in the super-high-frequency (SHF) absorption spectrum of helium is related to the creation of c-rotons. A possible interpretation of the Stark effect observed for the roton line is also proposed. Keywords: liquid 4 He, microwave resonator, circular roton, supernarrow absorption line. I. INRODUCTIONIn the recent works [1,2], an unconventional effect was discovered. In a dielectric disk-shaped resonator placed in liquid 4 He, the azimuth (l-)modes were excited. These modes are of the "whispering-gallery" type and represent a superposition of standing and running resonance electromagnetic (EM) waves of the SHF range in a narrow frequency interval. At the roton frequency ν rot = ∆ rot /2π = 180.3 GHz, the supernarrow absorption line with the width △ν ≃ 50 kHz was observed in the SHF spectrum of the resonator. This width is by six orders less than that of a roton peak measured in neutron experiments and is comparable with the width of line in the Mössbauer effect. It was assumed in [2] that the line is related to the Van Hove singularity caused by a high density of states of plane (p-) rotons near the roton minimum of the dispersion curve. In this case, however, one is faced with the problem to satisfy the momentum conservation law, since the p-roton momentum is greater than the momentum of a p-photon with the same energy by six orders. Therefore, it was supposed [2] that the excess momentum of a p-roton is transferred to helium as a whole.To clarify this and other points, it is necessary to calculate the probability of the creation of a roton and the widths and the forms of lines for various possible processes, and then to choose a process explaining the experiment. It is necessary to take into account that the EM field of a disk-shaped resonator has the circular (c-) symmetry and is concentrated only near the disk according to measurements [1] and the theory [3]. Since namely * Electronic address: vloktev@bitp.kiev.ua † Electronic address: mtomchenko@bitp.kiev.ua the EM field induces the transition, the latter must be characterized by the c-symmetry. In [3], it was shown that a phonon near a disk possesses also the c-symmetry. Therefore, we assume that the narrow line corresponds to the creation of a c-roton by the EM field of the resonator. Below, we will find the probability of this process and the width of the corresponding absorption line. A number of results required for calculations was obtained in [3]; formulas (N) from that work will be denoted...

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Section: Width Of the Roton Absorption Linementioning

confidence: 92%

Section: Probability Of the Creation Of A Circular Phonon By The mentioning

confidence: 99%

Section: ∂ ∂R1mentioning

confidence: 99%

“…In the recent works [1,2], an unconventional effect was discovered. In a dielectric disk-shaped resonator placed in liquid 4 He, the azimuth (l-)modes were excited.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Theory of a supernarrow roton absorption line in the spectrum of a disk-shaped microwave resonator

Локтев

Tomchenko

2010

Phys. Rev. B

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Microwave Spectroscopy of Condensed Helium at the Roton Frequency

et al. 2009

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Some Mechanisms of “Spontaneous” Polarization of Superfluid He-4

Tomchenko

2009

J Low Temp Phys

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Previously, a quantum "tidal" mechanism of polarization of the atoms of He-II was proposed, according to which, as a result of interatomic interaction, each atom of He-II acquires small fluctuating dipole and multipole moments, oriented chaotically on the average.In this work, we show that, in the presence of a temperature or density gradient in He-II, the originally chaotically oriented tidal dipole moments of the atoms become partially ordered, which results in volume polarization of He-II. It is found that the gravitational field of the Earth induces electric induction △ϕ ∼ 10 −7 V in He-II (for vessel dimensions of the order of 10 cm). We study also the connection of polarization and acceleration, and discuss a possible nature of the electric signal △ϕ ≈ k B △T /2e observed by A. S. Rybalko in experiments with second sound.

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Resonance absorption of microwaves inHeII: Evidence for roton emission

Cited by 58 publications

References 16 publications

Theory of a supernarrow roton absorption line in the spectrum of a disk-shaped microwave resonator

Theory of a supernarrow roton absorption line in the spectrum of a disk-shaped microwave resonator

Microwave Spectroscopy of Condensed Helium at the Roton Frequency

Some Mechanisms of “Spontaneous” Polarization of Superfluid He-4

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