Mercury-Based Cuprate High-Transition Temperature Grain-Boundary Junctions and SQUIDs Operating Above 110 Kelvin

Area of Science:

• Materials Science
• Condensed Matter Physics
• Superconductivity

Background:

• HgBa(2)CaCu(2)O(6+delta) (Hg-1212) is a high-temperature cuprate superconductor.
• Grain boundaries in superconductors can act as weak links, affecting critical current density.
• Superconducting Quantum Interference Devices (SQUIDs) are sensitive magnetic flux detectors.

Purpose of the Study:

• To investigate the superconducting transport properties of HgBa(2)CaCu(2)O(6+delta) films and grain-boundary junctions.
• To fabricate and characterize SQUIDs using these grain-boundary junctions.
• To assess the potential of these devices for practical applications.

Main Methods:

• Growth of HgBa(2)CaCu(2)O(6+delta) films on SrTiO(3) bicrystal substrates.
• Measurement of critical current density and zero-resistance temperature.
• Fabrication and testing of direct-current SQUIDs.

Main Results:

• HgBa(2)CaCu(2)O(6+delta) films exhibit zero-resistance temperatures around 120 K and high critical current densities (10^6 A/cm^2 at 100 K).
• Grain boundaries act as weak links, reducing critical current by up to three orders of magnitude.
• Fabricated SQUIDs operate up to 111.8 K and show clear magnetic field responses.

Conclusions:

• HgBa(2)CaCu(2)O(6+delta) grain-boundary junctions exhibit weak-link behavior suitable for SQUID fabrication.
• High operating temperatures of HgBa(2)CaCu(2)O(6+delta) SQUIDs make them promising for portable sensors and devices with non-conventional cooling.
• Further research can optimize these devices for enhanced performance and broader applications.