Observation of folded Fermi surface in the pseudogap state of high-Tc superconductor

我们用角分辨光电子能谱研究了高T_c超导体的赝隙态，得到了如下实验结果。(1)我们观察到与超导和赝隙相对应的两个不同的能隙共存。(2)阐明了多层铜酸盐的能隙结构，发现了一个与T_c成正比的参数。(3)在电子掺杂的铜酸盐中，随着退火温度的增加，伪隙消失。这表明了超导和伪隙之间的竞争。

We have investigated the pseudogap state of high-Tc superconductors by angle-resolved photoemission spectroscopy and have obtained experimental results as below. (1) We have observed a coexistence of two distinct energy gaps corresponding to the superconducting and pseudogap. (2) The energy gap structure of the multilayer cuprate has been clarified and we have found a parameter which scales with Tc. (3) While the Tc increases by annealing in the electron-doped cuprates, a disappearance of the psedogap has been observed. This indicates a competition between the superconductivity and the pseudogap.