4He Fluid in Extremely Narrow 1D Channels 1.5 nm in Diameter
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To examine whether one-dimensional (1D) helium quantum fluid is realized in narrower channels than those studied previously, we have measured heat capacities of 4He adsorbed in nanoporous material FSM with straight 1D channels 1.5 nm in diameter. From the heat of desorption for adsorbed 4He, the coverage n f, up to which 4He film grows in the channels, is determined to be 15.4 μmol/m2 using the Frenkel-Halsey-Hill model. At coverages sufficiently below n f, the temperature dependence of the 4He heat capacity has a shoulder, above which adsorbed 4He is delocalized from the substrate. On the other hand, the depression of the heat capacity indicating quantum effects has not been observed up to n f, which suggests that 4He film in the channels remains amorphous-like normal fluid. Just above n f, the quantum effect is observed in 4He adatoms on the grain surface of FSM powder, which indicates that 1.5 nm channels are slightly below the limit required to realize quantum effect in the inside 4He fluid.
Keywords4He film One-dimensional state Quantum fluid Nano-scale channel
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- 3.N. Wada, Y. Minato, T. Matsushita, M. Hieda, J. Low Temp. Phys. (2010) in this volume Google Scholar