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

我们已经建立了一个低温和高分辨率的光电子能谱（PE）使用激光作为光子源。在没有光的能量宽度的情况下，我们获得了0.8meV的能量分辨率，0.2度的角分辨率，最低样品温度为4K，这是目前世界上性能最好的PE谱仪，我们用它研究了低转变温度（low-Tc）超导体。我们观察到了元素金属（Nb和Pb）的超导能隙以及Pb中声子诱导的精细结构。从杂质引起的禁带各向异性的变化，我们得出了YNi_2B_2C的各向异性s波超导电性。为MgB_2的多重能隙提供了光谱证据。我们测量了Ba_ K_xBiO_3晶体的各向同性s波带隙和正常态赝带隙<1-x>。我们观察到Ba_8Si_3的超导能隙<46>，并将其归类为弱耦合超导体。通过对2 H-NbSe_2的角分辨研究，我们解决了所有由能带结构计算预测的费米面片，并观察到了FS片依赖的超导电性。

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.