Development of ultrahigh-resolution photoemission spectrometer and study of quasiparticles in high-temperature superconductors

为了阐明高温超导体中准粒子的起源，我们在东北大学建造了一台新的超高分辨率角度分辨光电子能谱(ARPES)。该光谱仪由(1)电子能量分析器、(2)光源、(3)分析室和(4)样品制备室组成。在分析仪方面，我们改进了半球部分和电子透镜系统的电稳定性，并对CCD相机和二维光电子探测器进行了准确的灵敏度标定。在光源方面，我们构建了一个双差分泵浦系统和一个真空紫外滤光器，它可以透过来自He放电灯的紫外线，但完全阻挡来自放电灯的残余气体。对于样品室，我们研制了一种变角机械手，它可以在低温下相对于分析仪旋转角度。为了有效地执行ARPES实验，我们使用了Devel…更多的人在样品制备室周围运行了样品转移系统。为了提高测量过程中的真空度和实现低温，我们用氦循环低温恒温器构建了多壁辐射屏蔽体。通过这些努力，我们最终获得了如下的高性能：(1)能量分辨率：1.3 MeV；(2)动量分辨率：0.005Å^&lt；-1；；(3)最低温度：3.7K；利用这台超高分辨率能谱仪，我们进行了以下方面的高分辨率ARPES测量：1)观测铋系高温超导体的费米面、超导能隙和赝隙；2)直接观测三层超导体上的Bogoliubov准粒子；Bi2223.3)阐明空穴掺杂高温超导体色散中扭结的来源；4)直接观测MgB_2中的多个超导能隙；2.5)观测Bi基高温超导体能量色散中的磁性同位素效应。6)直接观测非单调dx2&lt；-y2&gt；电子掺杂高温超导体中的波超导带隙。较少

In order to clarify the origin of quasiparticles in high-temperature superconductors, we have constructed a new ultrahigh-resolution angle-resolved photoemission (ARPES) spectrometer at Tohoku University. The spectrometer consists of (1) electron-energy analyzer, (2) light source, (3) analysis chamber, and (4) sample preparation chamber. As for the analyzer, we have improved the electric stability of the hemispherical part and the electron lens system, and also performed accurate sensitivity calibration of the CCD camera and the two-dimensional photoelectron detector. As for the light source, we have constructed a double differential pumping system as well as a VUV-filter which can pass ultraviolet-ray from the He discharge lamp but completely blocks residual gasses from the lamp. As for the sample chamber, we have developed a variable-angle manipulator which can rotate the angle with respect to the analyzer at low temperature. To effectively perform the ARPES experiment, we have devel … More oped a sample transfer system around the sample preparation chamber. To improve the vacuum during the measurement and to achieve low temperature, we have constructed multi-wall radiation shields with He-cycling cryostat. By making these efforts, we have finally achieved high performances as follows : (1) energy resolution : 1.3meV, (2) momentum resolution : 0.005Å^<-1>, (3) lowest temperature : 3.7K, and (4) vacuum during measurements : 2x10^<-11>Torr. By using this ultrahigh-resolution spectrometer, we have performed high-resolution ARPES measurements on following subjects.1)Observation of Fermi surface, superconducting gap, and pseudogap in Bi-based high-temperature superconductors.2)Direct observation of Bogoliubov quasiparticles on a triple-layered superconductor Bi2223.3)Elucidation of the origin of kink in the dispersion in hole-doped high-temperature superconductors.4)Direct observation of multiple-superconducting gaps in MgB_2.5)Observation of magnetic isotope effect in energy dispersion of Bi-based high-temperature superconductors.6)Direct observation of nonmonotonic d_x2_<-y2> wave superconducting gap in electron-doped high-temperature superconductors. Less