Size effects in superfluid 3He films.
Size effects in superfluid 3He films.
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超流体 3He 薄膜中的尺寸效应。
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
Richardson
中科院分区：
文献类型：
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作者：
Freeman;Richardson
本文讨论了两个相关的问题。一个是小几何形状对{sup 3}He超流相的影响，另一个是{sup 3}He准粒子在表面的散射性质。我们进行测量的300 nm厚的薄膜的{sup 3}他通过限制紧密间隔的聚酯薄膜之间的液体。通过两种方法同时探测流体。核磁共振监测系统的自旋动力学，产生的信息，我们确定超流体相。在这种情况下，液体信号必须与吸附表面层的信号分离，通过自旋交换将其平均。流体的流体动力学响应由扭摆的周期和阻尼确定，扭摆产生基底的振荡运动。在正常和超流相一样，这种响应强烈依赖于准粒子与表面相互作用的微观细节。我们比较的超流测量的金斯堡-朗道模型，其中的顺序参数消失在墙壁（扩散边界条件）。超流转变温度、超流密度和核磁共振频移的计算结果与理论计算值吻合较好。与理论雅阁，我们发现超流{ital A}相在很宽的压力和温度范围内被壁稳定，在此范围内{ital B}相在体相中是稳定的。然而，与计算相反，我们没有观察到{ital A}-{ital B}相界。在这些实验中，通过引入少量的{sup 4}He来修改{sup 3} He-衬底界面。{sup 4}低温下，He优先沉积在表面，这种效应会持续到形成几个原子深的层为止。«少
This paper addresses two related problems. One is the effect of small geometries on the superfluid phases of {sup 3}He, and the other is the nature of the scattering of {sup 3}He quasiparticles at surfaces. We perform measurements on 300-nm-thick films of {sup 3}He created by confining the liquid between closely spaced Mylar sheets. The fluid is probed simultaneously by two methods. Nuclear magnetic resonance monitors the spin dynamics of the system, yielding information with which we identify the superfluid phase. In this case, the liquid signal must be separated from that of the adsorbed surface layer, with which it is averaged by spin exchange. The hydrodynamic response of the fluid is determined from the period and damping of a torsion pendulum, which generates oscillatory motion of the substrate. In the normal and superfluid phases alike, this response is strongly dependent on microscopic details of the quasiparticle interactions with the surface. We compare the superfluid measurements to the Ginzburg-Landau model in which the order parameter vanishes at the walls (the diffusive boundary condition). Results for the superfluid transition temperature, the superfluid density, and the NMR frequency shift are in good quantitative agreement with the theory. Also in accord with themore » theory, we find that the superfluid {ital A} phase is stabilized by the walls over a wide range of pressures and temperatures at which the {ital B} phase is stable in bulk. In contrast with the calculations, however, we do not observe the {ital A}-{ital B} phase boundary. The {sup 3}He-substrate interface is modified in these experiments by the introduction of small quantities of {sup 4}He. {sup 4}He plates out preferentially on the surfaces at low temperatures, an effect that persists until a layer several atoms deep has been built up.« less