Investigating quantum phase transitions using designer-anvil pressure cells

关联电子系统研究中的发现发生在已知低温态的边界上。除了外加磁场，压力可以精确控制晶格密度，是穿越量子物质相图和寻找新的物质状态的首选工具。该项目代表了高压砧座技术的一个根本性的出发点：我们将通过微光刻方法将引线和检测电路结构化到陶瓷砧座中。由此产生的设计师砧提供的可靠性，易用性和多功能性所需的一种新的调查到高压超导状态的原型相关电子超导体CeCu 2Si 2。在这种有趣的材料中，似乎有两种不同的机制可以在压力-温度相图的不同区域诱导超导性。这两种相互作用都起源于电子之间的库仑排斥，但是一种-有效的磁相互作用-在材料被调谐接近磁序的开始时占主导地位，而另一种-有效的电荷密度相互作用-在晶格的假定转变附近占主导地位，其中晶胞体积和晶格密度经历弱的一阶变化。为了研究CeCu 2Si 2和相关材料中的密度变化量子相变，将在100 kbar范围内对电阻率、热容和热膨胀的压力依赖性进行详细研究。虽然研究的配对机制可能在整个强相关电子场（包括高Tc超导体）中产生影响，但设想的高压技术将有利于对砧座条件下的运输或热力学实验感兴趣的大量研究人员。

Discovery in correlated electron systems research occurs on the boundary of known low temperature states. Next to applied magnetic field, pressure, which affords precise control over the lattice density, is the vehicle of choice for traversing quantum matter phase diagrams and seeking out novel states of matter. This project represents a radical departure in high pressure anvil cell technology: We will structure leads and detection circuits into ceramic anvils by microlithographic methods. The resulting designer anvils provide the reliability, ease of use and versatility necessary for a novel investigation into the high-pressure superconducting state of the archetypal correlated electron superconductor CeCu2Si2. In this intriguing material it appears that two distinct mechanisms can induce superconductivity in different regions of the pressure-temperature phase diagram. Both interactions originate in the Coulomb repulsion between electrons, but one - an effective magnetic interaction - dominates when the material is tuned close to the onset of magnetic order, while the other - an effective charge density interaction - prevails close to a putative transition of the lattice, in which the unit cell volume and hence the lattice density undergoes a weak first order change. In order to investigate the density change quantum phase transition in CeCu2Si2 and in related materials, a detailed study of the pressure dependence of resistivity, heat capacity and thermal expansion will be carried out into the 100 kbar regime. While the investigated pairing mechanism may have ramifications throughout the strongly correlated electron field, including the high-Tc superconductors, the envisaged high pressure technology will be beneficial for a large community of researchers interested in transport or thermodynamic experiments under anvil cell conditions.