Regensburg 2019 – wissenschaftliches Programm
TT 57.11: Vortrag
Donnerstag, 4. April 2019, 17:45–18:00, H7
Local Magnetic Measurements of Trapped Flux Through a Permanent Current Path in Graphite — •Markus Stiller, José Barzola-Quiquia, Pablo D. Esquinazi, and Christian E. Precker — Felix-Bloch Institute for Solid-state Physics, Universität Leipzig, Linnestr. 5, D-04103, Germany
Measurements of the electrical resistance of different natural graphite samples suggest the existence of superconductivity at room temperature in some regions of the samples. To verify whether dissipationless electrical currents are responsible for the trapped magnetic flux, we localized them using magnetic force microscopy on a natural graphite sample in remanent state after applying a magnetic field. The results indicate that at room temperature a permanent current flows at the border of the trapped flux region. The current path vanishes at the same transition temperature Tc=370 K as the one obtained from electrical resistance measurements on the same sample. Magnetic coupling is excluded as origin of the observed phase signal. Time-dependent measurements of the signal show the typical behavior of flux creep of a permanent current flowing in a superconductor. The overall results support the existence of room-temperature superconductivity at certain regions in the graphite structure.