High-pressure charge distribution in YBa2Cu3O6+y by NMR

通过 NMR 观察 YBa2Cu3O6 y 中的高压电荷分布

基本信息

批准号：
317319632
负责人：
Professor Dr. Jürgen Haase
金额：
--
依托单位：
Felix-Bloch-Institut für Festkörperphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/317319632?language=en
关键词：
pressure charge distribution YBa2Cu3O6+y NMR

项目摘要

We propose to quantitatively determine how the application of external pressure changes the local charge distribution in the CuO2 plane in the cuprate high-temperature superconductor YBa2Cu3O6+y. Pressure, chemically induced as well as externally applied, has a very prominent role in cuprate physics, since it not only induces the highest critical temperatures of superconductivity (Tc) in these materials, but even led to the discovery of new materials. However, it is not clear how pressure affects the changes in the properties of the cuprates. NMR is a very powerful probe in cuprate research, but its use with the necessary high pressures became available only very recently. In a first experiment in 2011, we showed the new capability with 17O NMR of YBa2Cu4O8 where we observed the vanishing of the pseudo gap features at about 7 GPa. Meanwhile, we have become world-leading in high-pressure NMR, having developed our own high-pressure NMR cells and also demonstrated their use with single crystal materials. Moreover, in 2014 we showed that the NMR quadrupole splittings at Cu and O provide a quantitative measure of local charges in the CuO2 plane in all cuprates, and that this distribution sets the maximum achievable Tc. This relates the charge distribution, which is a material chemistry parameter, to the superfluid density, a property measured at very low temperatures in superconducting samples, reproducing Uemura's famous relation. Consequently, we are now in a position to find out what happens to the charge and its distribution in the cuprates at pressures that change Tc significantly. With the proposed research it will be revealed whether indeed a change in doping or an intraplanar charge redistribution between Cu and O, or suppression of charge order that is believed to compete with superconductivity is responsible for the change in Tc. The results will not only clarify the role of pressure in cuprate physics, but also help in understanding what sets the maximum Tc. Furthermore, we will be able to quantitatively investigate a possible formation of static charge density waves in these materials, and their response to external pressure.

我们建议定量确定外部压力的应用如何改变Cuo2平面中的局部电荷分布，高温超导体YBA2CU3O6+y。压力（化学诱导和外部应用）在铜质物理学中具有非常重要的作用，因为它不仅在这些材料中诱导了超导性（TC）的最高临界温度，而且甚至导致了新材料的发现。但是，尚不清楚压力如何影响丘比特的特性变化。 NMR是铜研究研究中非常有力的探测器，但是它与必要的高压一起使用，直到最近才能使用。在2011年的第一个实验中，我们展示了新的功能，其中17o nmr的YBA2CU4O8 NMR在大约7 GPA处观察到了伪间隙特征的消失。同时，我们已经开发了自己的高压NMR细胞，在高压NMR中成为世界领先的，并且还证明了它们与单晶材料的使用。此外，在2014年，我们展示了Cu和O的NMR四极分裂提供了所有丘脑中CuO2平面中局部电荷的定量度量，并且此分布设置了最大可实现的TC。这将电荷分布（即物质化学参数）与超流体密度（在超导样品中非常低的温度下测量的特性）相关联，重现了Uemura著名的关系。因此，我们现在可以找出电荷会发生什么及其在铜矿中的分布发生的情况，这会大大改变TC的压力。通过拟议的研究，将揭示出Cu和O之间掺杂或载液内电荷重新分布的情况，还是抑制与超导性竞争的电荷顺序是导致TC的变化。结果不仅将阐明压力在铜物理学中的作用，还可以帮助理解最大TC的原因。此外，我们将能够定量研究这些材料中静态电荷密度波的可能形成，及其对外部压力的反应。