Construction of ultrahigh-resolution photoemission spectrometer with small spot size using laser as a photon source

我们构建了一台以激光为光子源的低温高分辨率光电发射光谱仪。我们实现了0.8 meV的无光能宽的能量分辨率，0.2度的角分辨率，4 K的最低样品温度，是目前世界上性能最高的PE光谱仪。利用该光谱仪，我们研究了低转变温度（low- tc）的超导体。我们观察到元素金属（Nb和Pb）的超导隙以及Pb中声子诱导的精细结构。我们从杂质引起的间隙各向异性变化中得出了Yni_2B_2C的各向异性s波超导性。我们提供了MgB_2存在多重间隙的光谱证据。我们测量了Ba_<1-x>K_xBiO_3中各向同性s波隙和正态赝隙。我们观察到Ba_8Si_<46>的超导间隙，并将其归类为弱耦合超导体。从2H-NbSe_2的角度分辨研究中，我们分辨出了所有由能带结构计算预测的费米表面片，并观察到FS片相关的超导性。

We have constructed a low-temperature and high-resolution photoemission (PE) spectrometer for using a laser as a photon source. We have achieved an energy resolution of 0.8 meV without an energy width of light\ an angular resolution of 0.2 degree, and the lowest sample temperature of 4 K, which are the highest performance of PE spectrometer in the world.Using this spectrometer, we have studied superconductors with a low transition temperature (low-Tc). We have observed a superconducting gap of elemental metals (Nb and Pb) as well as phonon-induced fine structures in Pb. We have concluded anisotropic s-wave superconductivity for Yni_2B_2C from an impurity-induced change in gap anisotropy. We have provided a spectroscopic evidence for a multiple gap of MgB_2. We have measured an isotropic s-wave gap and a normal-state pseudogap in Ba_<1-x>K_xBiO_3. We have observed the superconducting gap of Ba_8Si_<46> and classified it as a weak coupling superconductor. From angle-resolved study of 2H-NbSe_2, we have resolved all the Fermi surface sheets predicted by band structure calculations and have observed FS sheet dependent superconductivity.