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arXiv · 1805.04188

Maxon and roton measurements in nanoconfined $^4$He

Matthew S. Bryan·Paul E. Sokol
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Abstract

We investigate the behavior of the collective excitations of adsorbed $^4$He in an ordered hexagonal mesopore, examining the crossover from a thin film to a confined fluid. Here we present the inelastic scattering results as a function of filling at constant temperature. We find a monotonic transition of the maxon excitation as a function of filling. This has been interpreted as corresponding to an increasing density of the adsorbed helium, which approaches the bulk value as filling increases. The roton minimum exhibits a more complicated behavior that does not monotonically approach bulk values as filling increases. The full pore scattering resembles the bulk liquid accompanied by a layer mode. The maxon and roton scattering, taken together, at intermediate fillings does not correspond to a single bulk liquid dispersion at negative, low, or high pressure.

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Matthew S. Bryan, Paul E. Sokol. 2018-05-10. Maxon and roton measurements in nanoconfined $^4$He. https://doi.org/10.1103/physrevb.97.184511

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