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Study of the Impurity Effect in Superfluid Helim 3

超流Helim 3中杂质效应的研究

基本信息

批准号：
12640356
负责人：
YANO Hideo
金额：
$ 2.37万
依托单位：
OSAKA CITY UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640356/
关键词：
superfluid helium 3 impurity effect aerogel p-wave of Couper pairs nuclear demag.cryostat ultralow temperature NMR melting curve thermometer 超流動^3He ^3He融解圧温度計

项目摘要

We have investigated the impurity effect in the p-wave superfluidity by measuring the fourth sound in superfluid in aerogels. We utilized aerogels with porosities of 97.5, 98 and 98.5 % as impurities of 2.5, 2 and 1.5 %, respectively, for superfluid ^3He. For the fourth sound experiment we have developed the mold method of aerogel into a cell.The ^3He fluid was cooled with a new design of a nuclear demagnetization cryostat which was machined from an oxygen free copper (OFC) rod with high purity. The nuclear stage was mounted in a dilution refrigerator after a heat treatment. Precooling was performed with the dilution refrigerator down to 16 mK in a high magnetic field of 8 T and then the nuclear stage was demagnetized adiabatically to low fields. After that we obtained the lowest temperature of 45 μK and maintained temperature below 250 μK over one month.We have found results in the present study as follows:1.Both the superfluid density and the transition temperature of are reduced if impurities are applied.2.These are decreased systematically with increasing impurities.The results suggest that impurities more restrict the p-wave superfluidity than s-wave one.We have presented the results in international meetings and discussed the impurity effect in the superfluid We have also published the results in scientific journals.

我们通过测量气凝胶超流体中的第四声，研究了 p 波超流中的杂质效应。对于超流体 ^3He，我们使用孔隙率为 97.5%、98% 和 98.5% 的气凝胶，杂质分别为 2.5%、2% 和 1.5%。对于第四个声音实验，我们开发了将气凝胶模制成电池的方法。^3He流体采用新设计的核退磁低温恒温器进行冷却，该低温恒温器由高纯度的无氧铜（OFC）棒加工而成。热处理后将核级安装在稀释冰箱中。使用稀释制冷机在 8 T 的高磁场中预冷至 16 mK，然后将核级绝热退磁至低磁场。此后，我们获得了最低温度45 μK，并在一个月内保持温度低于250 μK。我们在本研究中发现以下结果：1.如果添加杂质，超流体密度和转变温度都会降低。2.随着杂质的增加，超流体密度和转变温度会系统性地降低。结果表明，杂质比横波超流性更能限制p波超流性。我们已经在国际会议上介绍了这一结果。并讨论了超流体中的杂质效应我们还在科学期刊上发表了结果。