Atomically thin superfluid helium films on solid hydrogen

• Published in: Physical review letters Vol. 67; no. 9; pp. 1118 - 1121
• Main Authors: SHIRRON, P. J, MOCHEL, J. M
• Format: Journal Article
• Language: English
• Published: Ridge, NY American Physical Society 26-08-1991
• Subjects: 08 HYDROGEN; 080800 - Hydrogen- Properties & Composition; 640450 - Fluid Physics- Superfluidity; ADSORPTION ISOTHERMS; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Condensed matter: structure, mechanical and thermal properties; ELEMENTS; EVEN-EVEN NUCLEI; Exact sciences and technology; Films (including physical adsorption); FLUIDS; HELIUM 4; HELIUM II; HELIUM ISOTOPES; HYDROGEN; ISOTHERMS; ISOTOPES; LIGHT NUCLEI; NONMETALS; NUCLEI; Physics; QUANTUM FLUIDS; Quantum fluids and solids; liquid and solid helium; SORPTIVE PROPERTIES; STABLE ISOTOPES; SURFACE PROPERTIES; THIN FILMS; THIRD SOUND; VAN DER WAALS FORCES; WETTABILITY; Liquid solid interface; Support; Hydrogen; Chemical bond; Crystals; Superfluid; Kosterlitz Thouless transition; Coverage rate; Experimental study; Helium; Thin film; Sound velocity; Adsorption; Van der Waals interaction; Isotherm; Chemical potential; Third sound
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.67.1118

We have measured both adsorption isotherms and third-sound resonance of atomically thin {sup 4}He films on solid hydrogen. We find helium more weakly bound to a hydrogen surface than to other rare-gas surfaces, with a van der Waals cofficient of 4.6{plus minus}0.4 K (layers){sup 3}. We have also measured third sound, at 0.18 K, down to a total helium coverage of 0.45{plus minus}0.01 atomic layer, indicating an inert coverage at {ital T}=0 K of 0.29 atomic layer or less. In common with other weak-binding substrates we also see depressions in third-sound velocity near half-layer intervals.