Superconducting Behavior of Interfaces in Graphite: Transport Measurements of Micro-constrictions

Understand

We have studied the magnetoresistance (MR) of thin highly oriented pyrolytic graphite mesoscopic samples without and with micro-constrictions of different widths between the voltage electrodes.

• The MR for fields parallel to the c-axis shows an anomalous hysteresis loop compatible with the behavior expected for granular superconductors.
• The smaller the constriction width the larger is the anomalous hysteresis and the higher the temperature for its observation.
• Our results support the existence of granular superconductivity probably embedded at interfaces between crystalline graphite regions.