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

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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.