Abstract
The heat capacity of a small number of atoms dissolved in a submonolayer film has been measured. The measured heat capacity is finite and suggests that atoms are mobile in an areal density regime higher than that of the phase, where films are believed to be solid. At higher areal densities, the measured heat capacity is proportional to and depends on the number of atoms. These behaviors are anomalous to that of a two-dimensional Fermi fluid and cannot be explained by uniform melting of films. One possible explanation for these anomalous behaviors is that helium atoms exhibit fluidity only inside the domain walls of the adsorption structure, and the dissolved atoms gather in them and behave as a one-dimensional Fermi fluid or as Dirac fermions, depending on the structure of the domain walls. The behaviors of the measured heat capacity strongly suggest this possibility.
- Received 16 August 2022
- Revised 2 November 2022
- Accepted 23 December 2022
DOI:https://doi.org/10.1103/PhysRevB.107.L020505
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