Kiss T, Shimojima T, Ishizaka K, Chainani A, Togashi T, Kanai T, Wang X-Y, Chen C-T, Watanabe S, Shin S
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Rev Sci Instrum. 2008 Feb;79(2 Pt 1):023106. doi: 10.1063/1.2839010.
We have developed a low temperature ultrahigh resolution system for polarization dependent angle-resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet (vuv) laser (hnu=6.994 eV) as a photon source. With the aim of addressing low energy physics, we show the system performance with angle-integrated PES at the highest energy resolution of 360 mueV and the lowest temperature of 2.9 K. We describe the importance of a multiple-thermal-shield design for achieving the low temperature, which allows a clear measurement of the superconducting gap of tantalum metal with a T(c)=4.5 K. The unique specifications and quality of the laser source (narrow linewidth of 260 mueV, high photon flux), combined with a half-wave plate, facilitates ultrahigh energy and momentum resolution polarization dependent ARPES. We demonstrate the use of s- and p-polarized laser-ARPESs in studying the superconducting gap on bilayer-split bands of a high T(c) cuprate. The unique features of the quasi-continuous-wave vuv laser and low temperature enables ultrahigh-energy and -momentum resolution studies of the spectral function of a solid with large escape depth. We hope the present work helps in defining polarization dependent laser excited angle-resolved photoemission spectroscopy as a frontier tool for the study of electronic structure and properties of materials at the sub-meV energy scale.
我们开发了一种用于偏振相关角分辨光电子能谱（ARPES）的低温超高分辨率系统，该系统使用真空紫外（vuv）激光（hnu = 6.994 eV）作为光子源。为了研究低能物理，我们展示了该系统在360 μeV的最高能量分辨率和2.9 K的最低温度下的角积分光电子能谱性能。我们描述了实现低温的多重热屏蔽设计的重要性，这使得能够清晰测量Tc = 4.5 K的钽金属的超导能隙。激光源的独特规格和品质（260 μeV的窄线宽、高光子通量），与一个半波片相结合，有助于实现超高能量和动量分辨率的偏振相关ARPES。我们展示了利用s偏振和p偏振激光ARPES研究高温超导铜酸盐双层分裂能带的超导能隙。准连续波光uv激光和低温的独特特性使得能够对具有大逃逸深度的固体的光谱函数进行超高能量和动量分辨率的研究。我们希望目前的工作有助于将偏振相关激光激发角分辨光电子能谱定义为在亚毫电子伏特能量尺度下研究材料电子结构和性质的前沿工具。
