Registered state and a two-dimensional Bose liquid of 4He in mesopores of hectorite.
Registered state and a two-dimensional Bose liquid of 4He in mesopores of hectorite.
复制标题
锂蒙脱石中孔中 4He 的注册态和二维玻色液体。
DOI：
10.1103/physrevb.52.1167
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Torii
中科院分区：
文献类型：
--
作者：
Wada;Inoue;Yano;Torii
用等量吸附热和热容方法研究了柱撑骨架层间距为17-20A的二维介孔中He原子的吸附和运动状态。由于中孔具有592msup2}/g的较大吸附面积，因此通过改变吸附原子的量进行了测量。结果表明，吸附原子集中在骨架层上的六角形注册位置，覆盖度高达0.4层。当覆盖度超过1.33+0.03层时，同位素效应对热容的影响和扭转振子的结果表明，{sup_4}He原子是超流的。在较低温度下，超流体的热容在T为二次项，在0.2或0.3K左右变为指数型，并与二维玻色粒子模型计算的二维声子和旋子热容进行了比较。比较表明，吸附原子的有效核直径为4-6A，并表明在2D吸附超流中原子间的关联比在体相干超流体中强得多。在完全吸附时，超流相变从{lambda}温度降低，这被认为是介孔大小对相干长度的影响。
In two-dimensional (2D) mesopores of hectorite that have an open spacing of 17--20 A between framework layers supported by pillars, the adsorption and motional state of {sup 4}He adatoms were studied by iso- steric heat of adsorption and heat capacity. These measurements were done by changing the amount of {sup 4}He adatoms, since the mesopores have quite a large adsorption area of 592{plus_minus}2 m{sup 2}/g. The results suggest that the adatoms are localized at hexagonal registered sites on the framework layers up to a coverage of 0.4 layer. At coverages exceeding 1.33{plus_minus}0.03 layers, the isotope effect on the heat capacity and the torsional oscillator result indicates superfluidity of the {sup 4}He adatoms. The heat capacity of the superfluid is quadratic in {ital T} at low temperatures and becomes exponential above around 0.2 or 0.3 K. The dependencies are compared with the 2D phonon and roton heat capacities of the model calculations for 2D Bose particles. The comparison shows the effective hard-core diameter of the adatoms to be 4--6 A, and indicates that the correlation among the atoms is much stronger in the 2D adsorbed superfluid than in bulk superfluid where the hard core is believed to be 2.56 A. Atmore » full adsorption, there was reduction of the superfluid transition {ital T}{sub {ital c}} from the {lambda} temperature, which was believed to be the effect of the size of the mesopores on the coherence length.« less