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Interaction of microwaves with superfluid flow in HeII
The absorption of 40–200GHz electromagnetic waves in liquid helium at temperatures 1.4–2.8K is investigated experimentally. The spectrum of oscillations of the “whispering gallery” modes of a dielectric disk-shaped resonator immersed in liquid helium is recorded. Superfluid flows in HeII is produced...
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| Published in: | Low temperature physics (Woodbury, N.Y.) N.Y.), 2008-04, Vol.34 (4), p.254-261 |
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| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | The absorption of 40–200GHz electromagnetic waves in liquid helium at temperatures 1.4–2.8K is investigated experimentally. The spectrum of oscillations of the “whispering gallery” modes of a dielectric disk-shaped resonator immersed in liquid helium is recorded. Superfluid flows in HeII is produced artificially using two “heat guns.” A narrow microwave absorption line has been detected at a frequency corresponding to the excitation energy of a single roton. It has been determined that the character of the resonance line changes radically as the velocity vs of the superfluid flow increases: microwave absorption was replaced by induced microwave emission, which was seen as a sharp intensification of the high frequency signal. The effect can be explained qualitatively on the basis of a two-level model of HeII. An abrupt change in the velocity of the superfluid flow is observed with continual increase of the power delivered to the heat gun. This could attest to quantization of vs. It is shown that the superfluid flow has a low-frequency effect on a microwave which outwardly is manifested as modulation of microwave oscillations. Possible reasons for this effect are analyzed. |
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| ISSN: | 1063-777X 1090-6517 |
| DOI: | 10.1063/1.2911649 |