Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Local Magnetic Measurements of Trapped Flux Through a Permanent Current
  Path in Graphite   Temperature and field dependent 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 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 $T_c\approx370$~K
as the one obtained from electrical resistance measurements on the same sample.
This sudden decrease of the phase is different from what is expected for a
ferromagnetic material. 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 and indicate
that magnetic force microscopy is suitable to localize them. Magnetic coupling
is excluded as origin of the observed phase signal.

11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio