Suppression of Superfluidity of 4He in a Nanoporous Glass by Preplating a Kr Layer
Suppression of Superfluidity of 4He in a Nanoporous Glass by Preplating a Kr Layer
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通过预镀 Kr 层抑制纳米多孔玻璃中 4He 的超流性
DOI：
10.1143/jpsj.80.084604
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发表时间：
2011
影响因子：
1.7
通讯作者：
Keiya Shirahama
中科院分区：
文献类型：
--
作者：
Yoshiyuki Shibayama;Keiya Shirahama
纳米多孔介质中的氦作为一种具有无序和约束的玻色体系引起了人们的广泛关注。在这里，我们研究了通过预镀单层氪来改变多孔结构如何影响吸附或限制在纳米多孔凝胶玻璃中的4he的超流体性质，这种玻璃具有直径为5.8 nm的三维相互连接的纳米孔网络。氮的吸附和解吸等温线表明，单层预镀的Kr将有效孔径减小到4.7 nm，孔径分布比裸Gelsil样品的尖锐分布扩大了约8倍。用扭振仪研究了单层Kr预镀前后吸附膜态和加压液态的超流体性质。在膜态下，预镀Kr可使超流转变温度和超流密度降低约10%。薄膜超流动性的抑制归因于4he原子的量子局域化，这是由预镀引起的孔径分布的加宽引起的基底电位的随机性。在高压液相中，预镀Kr能使超流体密度ρ增大10%，而在所有压力下，超流体密度ρ均减小2%。ρsmi的意外增强可能表明存在未知的受限he紊乱效应。
Helium in nanoporous media has attracted much interest as a model Bose system with disorder and confinement. Here we have examined how a change in porous structure by preplating a monolayer of krypton affects the superfluid properties of4He adsorbed or confined in a nanoporous Gelsil glass, which has a three-dimensional interconnected network of nanopores of 5.8 nm in diameter. Isotherms of adsorption and desorption of nitrogen show that monolayer preplating of Kr decreases the effective pore diameter to 4.7 nm and broadens the pore size distribution by about eight times from the sharp distribution of the bare Gelsil sample. The superfluid properties were studied by a torsional oscillator for adsorbed film states and pressurized liquid states, both before and after the monolayer Kr preplating. In the film states, both the superfluid transition temperatureTcand the superfluid density decrease about 10% by Kr preplating. The suppression of film superfluidity is attributed to the quantum localization of4He atoms by the randomness in the substrate potential, which is caused by the preplating-induced broadening of the pore size distribution. In the pressurized liquid states, the superfluid density ρsis found to increase by 10% by Kr preplating, whereasTcis decreased by 2% at all pressures. The unexpected enhancement of ρsmight indicate the existence of an unknown disorder effect for confined4He.