Development of Low Temperature Scanning Tunneling/Magnetic Force Microscope to Observe Magnetic Flux Lattice in High Temperature Superconductor

Pancake理论是描述高温超导体中磁通行为的著名理论之一，它预言了高温超导体中围绕磁通形成的涡旋-反涡对。我们研制了可以检测磁场力的低温扫描隧道显微镜，用于观测高温超导体中预测的涡旋-反涡旋对。在项目的第一年，我们对MFM的悬臂梁与超导体中的磁通相互作用进行了理论研究。确定了磁力显微镜检测磁通的合适条件。(2)研制了低温扫描隧道显微镜。在项目的第二年(即项目的最后一年)，(1)将低温扫描隧道显微镜改进为低温原子力显微镜。研制了一种新型的悬臂梁弯曲检测装置，可以在任何温度下工作。(2)几种能够检测磁力、静电场、侧向力等力的悬臂梁：用来测试所研制的装置的性能。

The Pancake theory that is one of the famous theory to describe the behavior of the magnetic flux in a high temperature superconductor predicts the formation of the vortex-antivortex pair around the magnetic flux in the high temperature superconductor. We develop the low temperature scanning tunneling microscope which can detect the magnetic force to observe the predicted vortex-antivortex pair in the high temperature superconductor.In the first year of the project, we did(1) Theoretical research of the interaction between the cantilever of MFM and a magnetic flux in a superconductor. The appropriate condition to detect the magnetic flux by MFM was determined.(2) The low temperature scanning tunneling microscope was developed. The apparatus give the preliminary results of the surface topology of the materials at liquid helium and liquid nitrogen temperatureIn the second year of the project (i.e., the last year of the project)(1) The low temperature scanning tunneling microscope was modified to low temperature atomic force microscope. A new mechanism was developed to detect the bending of the cantilever, which can work at any temperature.(2) Several types of cantilevers which can detect variety of force, i.e., magnetic force, static electric field, lateral force, etc. : to test the performance of the developed apparatus.