Fig1. Big-momentum and Ultralow-temperature Laser angle resolved photoemission spectroscopy

Angle Resolved Photoemission Spectroscopy (ARPES) is a powerful tool to detect the electronic structure directly in the condensed matter physics and material science. In the frontiers of physics research, such as high temperature superconductivity mechanism, the origin of the classical resistivity, spin characters and edge state of topological insulators, ARPES plays the very important roles.
Deep ultraviolet laser is an important light source with very high flux, very high energy resolution. Its use in the ARPES will push this experimental method to higher level. But there are two obvious deficiencies which restrict the further applications of laser ARPES. One is that the photo energy of the laser is not big enough to measure the electron structures around the corner of Bullion zone, where some key information should be measured to clarify some important physical questions. On the other hand, the lowest temperature of the sample (~ 10K) is still a little high. These two factors not only limit the development of the AREPS technology, but also restrict the research of many important physical phenomena.
The goal of our new project is to break down these two limits. In the base of our rich deep ultraviolet laser ARPES experience, we will push our new laser ARPES to another high level: develop the first big-momentum and ultralow-temperature laser ARPES in the world. This new instrument will include three important parts:
1) New deep ultraviolet laser source. The energy of photo will reach 7.5eV which is big enough to measure the electronic structure around the antinode region. 7.5eV photo energy of the new laser is record high in the solid state laser. It will be the first using in our new system in the world.
2) He-3 ultralow-temperature cryostat. The lowest temperature of sample will be lower than 1K, reach about 600-800mK. This is the lowest sample temperature in the APPES experiments all over the world till now. Around this low temperature, many important advanced physical researches, like high temperature superconductivity mechanism, quantum transition and heavy fermion superconductivity, will be further carried on.
3) New R8000 analyzer. It is the best analyzer in the world which can get less than 0.1meV energy resolution. It will be installed in our new system.
This development of new laser ARPES will ensure our leading position of ARPES technology in the world. Many important physical researches will be carried out and much more important results will be published…..