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

TL;DR

This study investigates the magnetoresistance of graphite with micro-constrictions, revealing hysteresis loops indicative of granular superconductivity at interfaces, with effects amplified in narrower constrictions and at higher temperatures.

Contribution

It provides experimental evidence of granular superconductivity at graphite interfaces using transport measurements on micro-constricted samples.

Findings

Hysteresis loops in magnetoresistance suggest granular superconductivity.

Narrower constrictions enhance the hysteresis effect.

Superconducting behavior persists at higher temperatures in smaller constrictions.

Abstract

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.