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Quantum Nucleation

量子成核

基本信息

批准号：
08240203
负责人：
SATOH Takeo
金额：
$ 50.82万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

Quantum nucleation is a kind of macroscopic quantum phenomenon accompanying the decay of metastable system described with a macroscopic variable, that is, the radius of a nucleus of the stable phase. The concept of quantum nucleation is currently applied in various field of physics. So, it is extremely important to obtain the unambiguous evidence of the phenomenon.The system of superfluid supersaturated ィイD13ィエD1He-ィイD14ィエD1He mixture is apparently the most prominent and unique system for observing the bulk quantum nucleation, in a condensed matter. Firstly, wall effects may be negligible because of the difference of zero-point energy between ィイD13ィエD1He and ィイD14ィエD1He atoms. That is, any surface is unlikely to be effective in nucleating the ィイD13ィエD1He-concentrated phase (c-phase). Secondly, our invented method to realize a supersaturated state of the ィイD13ィエD1He-dilute phase (d-phase) is a pressure sweep method, in which we can control the sweep rate so slowly that the almost quasis … More tatic condition is realized.Here, we report the results of the systematic study of the phase separation from supersaturated superfluid ィイD13ィエD1He-ィイD14ィエD1He mixtures of d-phase. The amount of critical supersaturation, ΔXィイD23ィエD2,cr was determined in the wide ranges of the temperature (400μK - 500mK) and the pressure (0 - 8kg・f/cmィイD12ィエD1). With the data we constructed the surface of critical supersaturation, ΔXィイD23ィエD2,cr (T,P), which enable us to recognize the overall features of critical supersaturation in superfluid ィイD13ィエD1He-ィイD14ィエD1He mixtures. The main specific features observed are as follows.(i) Below about 10mK, ΔXィイD23ィエD2,cr is almost independent of temperature.(ii) Above about 10mK, ΔXィイD23ィエD2,cr increases with temperature.The first fact was analyzed with the theory by Nakamura et al. semi-quantitably. It is shown that the phase-separation observed by us below about 10mK is triggered by quantum nucleation. The second fact suggests the effect of dissipation on the nucleation process. Burmistrov and Satoh theoretically discussed that effect by considering the second sound mode and the diffusion of ィイD13ィエD1He atoms in the d-phase. Our recent experimental investigation on the dynamics of the interface between the c-and d-phases strongly supports that consideration. Less

量子成核是伴随着亚稳系统衰变的一种宏观量子现象，用一个宏观变量，即稳定相的核半径来描述。量子成核的概念目前已应用于物理学的各个领域。因此，获得这一现象的明确证据至关重要。超流体过饱和イD13 D1 He-イD14 D1 He混合物系统显然是观察凝聚态物质中体量子成核的最突出和独特的系统。第一，壁效应可以忽略不计，这是因为在D13和D14两个原子之间存在零点能的差异。也就是说，任何表面都不可能有效地使α-D13 β-D1 He-浓缩相（c-相）成核。第二，我们发明的实现氦D13氦D1 He稀相（d相）过饱和状态的方法是压力扫描方法，其中我们可以控制扫描速率如此之慢，使得几乎准饱和的氦D13氦D1 He稀相（d相）的过饱和状态可以通过压力扫描方法来实现。 ...更多信息本文报道了超流超流体D_13He_（13）He-D_14He_（14）He_（11）He混合物中d相的相分离的系统研究结果。在温度（400μK -500 mK）和压力（0 - 8 kg·f/cm ~ 2·cm ~（-1）范围内测定了临界过饱和度ΔX_（23）_（24利用这些数据，我们构造了临界过饱和曲面ΔX_（13）_（14）_（13）_（14）_（13）_（14）_（13）_观察到的主要具体特点如下。(i)在10 mK以下，ΔX_（max）D_（23）_（max）D_（23）_（max）几乎与温度无关。(ii)在10 mK以上，ΔX_（max）D_（23）D_（2，cr）随温度的升高而增大，第一个事实用中村等人的理论进行了半定量分析。结果表明，在10 mK以下所观察到的相分离是由量子成核所触发的。第二个事实表明了耗散对成核过程的影响。Burmistrov和Satoh从理论上讨论了这种效应，考虑了第二声模和d相中的D13-D1 He原子的扩散。我们最近的实验研究之间的c-和d-阶段的界面的动力学强有力地支持这一考虑。少