Local magnetic measurements of permanent current paths in a natural graphite crystal

TL;DR

This study provides magnetic evidence of persistent current paths in natural graphite at room temperature, supporting the hypothesis of localized superconductivity near 370 K, using magnetic force microscopy to visualize flux trapping.

Contribution

It demonstrates the use of magnetic force microscopy to localize and confirm room-temperature superconducting regions in natural graphite, correlating magnetic and electrical transition data.

Findings

Persistent current flows at room temperature in graphite

Current paths vanish at transition temperature ~370 K

Method effectively localizes superconducting regions

Abstract

A recently reported transition in the electrical resistance of different natural graphite samples suggests the existence of superconductivity at room temperature. To check whether dissipationless electrical currents are responsible for the trapped magnetic flux inferred from electrical resistance measurements, we localized them using magnetic force microscopy on a natural graphite sample in remanent state after applying a magnetic field. The obtained evidence indicates 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 $T_c \simeq 370~$K as the one obtained from electrical resistance measurements on the same sample. The overall results support the existence of room-temperature superconductivity at certain regions in the graphite structure and show that the used method is suitable to localize the superconducting regions.