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High Pressure Transport Measurements on Strongly Correlated Electron Systems

强相关电子系统的高压输运测量

基本信息

批准号：
EP/D059844/1
负责人：
Emma Pugh
金额：
$ 17.65万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FD059844%2F1
关键词：
Pressure Transport Measurements Strongly Correlated

项目摘要

A conventional phase transition, e.g. the melting of a solid to liquid as heat is applied, involves moving from an ordered, low entropy state to a disordered, high entropy state when temperature is increased. Quantum phase transitions are different in that the change of phase brings with it no change in entropy at zero Kelvin and thus we are effectively moving from one (conventional) ordered state, to another (subtle or hidden ) ordered state. The transformation can occur at fixed temperature and as a function of some other control parameter, such a hydrostatic pressure or chemical composition. When the transitions occur the nature of the ordered state can be dramatically altered producing unconventional superconductivity and other new forms of novel quantum order which deviate from the standard low temperature theory of matter known as Landau's Fermi Liquid theory. Such ordered states can occur, for example, in systems that are on the border of magnetic long range order. The aim is to investigate current open questions on a number of materials close to magnetic instabilities which are likely to exhibit novel forms of quantum order and unconventional forms of superconductivity by use of high pressure and low temperature techniques. The work will also lead to advancements in high pressure diamond anvil cell techniques, in particular with respect to resistivity and AC-susceptibility methods. The grant will also allow for improvements in cryogenic methods with the completion of a new double stage adiabatic demagnetisation refrigerator capable of achieving a base temperature of 2-5 mK. Temperatures below 50 mK may be necessary to observe the new quantum states of interest.

传统的相变，例如当加热时固体熔化成液体，当温度升高时，涉及从有序的低熵状态到无序的高熵状态的转变。量子相变的不同之处在于，在零开尔文时，相变不会带来熵的变化，因此我们实际上是从一个(传统的)有序状态转移到另一个(微妙的或隐藏的)有序状态。这种转变可以在固定的温度下发生，也可以作为一些其他控制参数的函数，如静水压力或化学成分。当跃迁发生时，有序状态的性质可能会发生巨大的变化，产生非传统的超导和其他新的量子有序形式，这些新形式背离了标准的低温物质理论，即朗道的费米液体理论。例如，这种有序状态可能出现在磁性长程有序的边界上的系统中。其目的是利用高压和低温技术，研究一些接近磁不稳定性的材料的当前悬而未决的问题，这些材料可能表现出新的量子有序形式和非传统形式的超导电性。这项工作还将导致高压金刚石压腔技术的进步，特别是在电阻率和交流敏感度方法方面。这笔赠款还将改进低温方法，完成一台新的双级绝热去磁制冷机，该制冷机能够达到2-5MK的基准温度。低于50mK的温度可能是观察新的感兴趣的量子态所必需的。