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

为了弄清高温超导体中准粒子的起源，我们在日本东北大学建立了一台新的超高分辨率角分辨光电发射光谱仪。该光谱仪由(1)电子-能量分析仪，(2)光源，(3)分析室，(4)样品制备室组成。在分析仪方面，我们改进了半球形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精确的灵敏度标定。在光源方面，我们搭建了双差动泵浦系统和紫外滤光器，可以通过He放电灯的紫外线，但完全阻挡了电灯的残留气体。对于样品室，我们开发了一种可变角度机械手，可以在低温下相对于分析仪旋转角度。为了有效地进行ARPES实验，我们在样品制备室周围设计了一个样品传递系统。为了提高测量时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。通过这些努力，我们最终实现了以下高性能：(1)能量分辨率：1.3meV,(2)动量分辨率：0.005Å^<-1>,(3)最低温度：3.7K,(4)测量期间的真空度：2x10^<-11>Torr。利用这台超高分辨率光谱仪，我们对以下受试者进行了高分辨率ARPES测量。1) bi基高温超导体的费米面、超导隙和赝隙的观测。(2)三层超导体bi2222.3上Bogoliubov准粒子的直接观察(3)空穴掺杂高温超导体色散中结的起源。(4) mgb_2中多重超导间隙的直接观测（2.5）bi基高温超导体能量色散的磁同位素效应观测。6)电子掺杂高温超导体非单调d_x2_<-y2>波超导隙的直接观测。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