Studies of Two Dimensional Quantum Fluids and Solids with Low Temperature LEED and STM

采用比热法研究了石墨吸附氦-3 （3He）和氦-4 （4He）的第一层和第二层低温量子相图。发现了二维3He的理论上意想不到的多体凝聚。此外，3He和4He的第二层均存在相应的固相，这也是第一性原理计算未曾预料到的。该相可能是具有零点缺陷的低密度量子固体。利用低温STM首次成功地对石墨上的单层氪进行了实距成像，确定了氪的吸附位点为石墨蜂窝晶格的空心位点。成功地完成了在稀释冰箱温度下工作的LEED仪器的可行性研究。

Low temperature quantum phase diagrams of the first and second layers of helium-3 (3He) and helium-4 (4He) adsorbed on graphite were studied by specific heat measurements. Theoretically unexpected many-body condensation of two-dimensional 3He was discovered. In addition, the existence of a commensurate solid phase in the second layer of both 3He and 4He was confirmed, which had also been unexpected from the first-principles calculations. This phase is presumably a low-density quantum solid with zero-point defectons.We succeeded in the first real-space imaging of monolayer of Krypton adsorbed on graphite with low temperature STM and confirmed the adsorption site of Kr to be the hollow site of graphite honeycomb lattice. A feasibility study of development of a LEED instrument which works at dilution refrigerator temperatures was successfully finished.