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Related Experiment Video

Updated: Feb 26, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids

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Excitations in Quantum Liquids.

Henry R Glyde1

  • 1Department of Physics and Astronomy, University of Delaware, Delaware, FRANCE.

Reports on Progress in Physics. Physical Society (Great Britain)
|July 14, 2017
PubMed
Summary
This summary is machine-generated.

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This review updates the understanding of elementary excitations in bulk liquid helium-4 (⁴He), focusing on how inelastic neutron scattering reveals collective and single-particle dynamics. It highlights the role of Bose-Einstein condensation in superfluidity and temperature-dependent properties.

Area of Science:

  • Condensed Matter Physics
  • Quantum Fluids
  • Low-Temperature Physics

Background:

  • The study of elementary excitations in quantum fluids like liquid helium-4 (⁴He) is crucial for understanding their unique properties.
  • Previous reviews in the early 1990s established foundational knowledge, necessitating an update on recent advancements.

Purpose of the Study:

  • To provide an updated review of the progress in measuring and interpreting elementary excitations in bulk liquid ⁴He over the past 25 years.
  • To synthesize current data, calculations, and understanding of these excitations, particularly since the early 1990s.

Main Methods:

  • Focus on inelastic neutron scattering (INS) as the primary experimental technique for probing excitations.
  • Analysis of both collective excitations (phonon-roton modes) and single-particle excitations.
Keywords:
******Bose-Einstein condensationcollective modesliquid 4Heneutron scattering

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Main Results:

  • Detailed characterization of the dynamic response of liquid ⁴He, from low-energy collective modes to high-energy single-particle excitations.
  • Determination of atomic momentum distribution and Bose-Einstein condensate fraction from single-particle excitations.
  • Emphasis on the significant role of Bose-Einstein condensation in shaping the phonon-roton mode and its temperature dependence.

Conclusions:

  • The review demonstrates the interplay between elementary excitations and macroscopic properties like superfluidity in ⁴He.
  • It highlights the utility of studying these excitations for testing fundamental calculations of quantum liquids.
  • Normal liquid ⁴He exhibits similarities with other quantum and classical liquids, offering broader comparative insights.