{"title":"A review of giant correlation-length effects via proximity and weak-links coupling in a critical system: 4He near the superfluid transition","authors":"J. Perron, M. Kimball, F. Gasparini","doi":"10.1088/1361-6633/ab3df5","DOIUrl":null,"url":null,"abstract":"We review measurements of 4He near the superfluid transition in arrangements whereby an array of weak links couple relatively larger, more bulk-like 4He regions. In contrast to experiments which focus on the dependence of the superflow on the chemical potential difference across the links, these studies focus on the specific heat of both the weak links and that of the larger coupled regions, as well as the behavior of the superfluid fraction within the weak links. The data show unexpected results which reflect a very long range coupling as well as modification of the weak link itself due to the proximity to bulk-like helium. One finds that while the three-dimensional correlation length , where , is involved in these long-range effects, the distance over which these can be seen is of the order of 100 to 1000 times . These results call into question our understanding of the meaning of the correlation length at a critical point as the ‘range’ over which information can propagate. These studies are the first to measure the thermodynamic properties of weak links for a critical system where fluctuations are important. They differ in essential ways with expectations from mean-field considerations. We compare results with other 4He measurements, with superconductors and the theoretical calculations of the Ising model.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":null,"pages":null},"PeriodicalIF":19.0000,"publicationDate":"2019-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"4","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Reports on Progress in Physics","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1088/1361-6633/ab3df5","RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 4
Abstract
We review measurements of 4He near the superfluid transition in arrangements whereby an array of weak links couple relatively larger, more bulk-like 4He regions. In contrast to experiments which focus on the dependence of the superflow on the chemical potential difference across the links, these studies focus on the specific heat of both the weak links and that of the larger coupled regions, as well as the behavior of the superfluid fraction within the weak links. The data show unexpected results which reflect a very long range coupling as well as modification of the weak link itself due to the proximity to bulk-like helium. One finds that while the three-dimensional correlation length , where , is involved in these long-range effects, the distance over which these can be seen is of the order of 100 to 1000 times . These results call into question our understanding of the meaning of the correlation length at a critical point as the ‘range’ over which information can propagate. These studies are the first to measure the thermodynamic properties of weak links for a critical system where fluctuations are important. They differ in essential ways with expectations from mean-field considerations. We compare results with other 4He measurements, with superconductors and the theoretical calculations of the Ising model.
期刊介绍:
Reports on Progress in Physics is a highly selective journal with a mission to publish ground-breaking new research and authoritative invited reviews of the highest quality and significance across all areas of physics and related areas. Articles must be essential reading for specialists, and likely to be of broader multidisciplinary interest with the expectation for long-term scientific impact and influence on the current state and/or future direction of a field.