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Journal of Zhejiang University SCIENCE A 2007 Vol.8 No.7 P.1065-1076

http://doi.org/10.1631/jzus.2007.A1065


Studying creation of bulk elementary excitation by heaters in superfluid helium-II at low temperatures


Author(s):  ZAKHARENKO A. A.

Affiliation(s):  International Institute of Zakharenko Waves, Krasnoyarsk 660037, Russia

Corresponding email(s):   aazaaz@inbox.ru

Key Words:  Superfluid helium-II, Bulk elementary excitations (BEEs), Low temperatures, Cooper pairing phenomenon, Non-dispersive Zakharenko waves


ZAKHARENKO A. A.. Studying creation of bulk elementary excitation by heaters in superfluid helium-II at low temperatures[J]. Journal of Zhejiang University Science A, 2007, 8(7): 1065-1076.

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author="ZAKHARENKO A. A.",
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T1 - Studying creation of bulk elementary excitation by heaters in superfluid helium-II at low temperatures
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DOI - 10.1631/jzus.2007.A1065


Abstract: 
In this paper, the obtained experimental results concerning creation of bulk elementary excitations (BEEs) in isotopically pure liquid 4He at low temperatures ~60 mK are discussed. Positive rotons’ (R+-rotons) creation by a pulsed heater was studied. Signals were recorded for the following quantum processes: quantum evaporation of 4He-atoms from the free liquid-helium surface by the BEEs of the liquid helium-II, and BEEs reflection from the free surface back into the bulk liquid. Typical signals are shown, and ratios of signal amplitudes are evaluated. For long heater pulses from 5 to 10 μs, appearance of the second atomic cloud consisting of evaporated 4He-atoms was observed in addition to the first atomic cloud. It is thought that the first atomic cloud of the evaporated helium atoms consists of very fast 4He-atoms with energies ~35 K evaporated by positive rotons with the special energies ~17 K (~2ER~2×8.6 K with ER representing the roton minimum energy) corresponding to the third non-dispersive Zakharenko wave. The second cloud of slower 4He-atoms was created by surface elementary excitations (SEEs or ripplons) possessing the special energies ~7.15 K representing the binding energy. It was assumed that such SEEs can be created by phonons incoming to the liquid surface with special energies ~6.2 K corresponding to the first non-dispersive Zakharenko wave, which can interact at the liquid surface with the same phonons already reflected from the surface for long heater pulses. Also, some pulsed-heater characteristics were studied in order to better understand the features of such heaters in low temperature experiments.

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