Superconducting Vortex-Charge Measurement Using Cavity Electromechanics.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Magnetic field penetration into superconductors forms flux vortices.
• Flux vortices are predicted to possess charged cores and generate dipole electric fields.
• Charge trapping in vortices is amplified in high-temperature superconductors (HTS).

Purpose of the Study:

• To directly detect and quantify charges within flux vortices in HTS.
• To utilize a sensitive cavity-electromechanical device for probing vortex properties.
• To investigate charge trapping mechanisms in high-temperature superconducting materials.

Main Methods:

• Integration of a mechanical resonator made of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (HTS) into a microwave circuit.
• Development of a cavity-electromechanical device leveraging the sensitivity of microwave cavities.
• Measurement of the electromechanical response of the resonator to detect vortex charges.

Main Results:

• Direct detection of charges within single flux vortices was achieved.
• The surface electric dipole moment per vortex core was quantified as approximately 30 $|e|a_{B}$.
• A vortex charge per CuO$_{2}$ layer of 3.7 × 10$^{-2}$|$e$ was determined.

Conclusions:

• The study provides direct experimental evidence for charged vortex cores in HTS.
• The developed cavity-electromechanical technique offers a sensitive method for probing superconducting phenomena.
• Quantification of vortex charge offers insights into charge dynamics in high-temperature superconductors.