Field-Tuned Superconductor-Insulator Transition with and without Current Bias

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• The superconductor-insulator transition (SIT) is a fundamental phenomenon in low-dimensional electron systems.
• Understanding the critical behavior of SIT is crucial for developing novel electronic devices.

Purpose of the Study:

• To investigate the magnetic-field-tuned superconductor-insulator transition in ultrathin beryllium films.
• To determine the critical exponents and universality classes of the transition under different bias current conditions.

Main Methods:

• Utilized quench condensation to prepare ultrathin beryllium films near 20 K.
• Performed finite-size scaling analysis in the zero-current limit and with applied dc bias currents.
• Measured critical sheet resistance and scaling exponent products.

Main Results:

• In the zero-current limit, the scaling exponent product (nuz) was found to be 1.35+/-0.10, with a critical sheet resistance (R(c)) of approximately 1.2R(Q) (where R(Q) is the quantum of resistance).
• In the presence of dc bias currents below the zero-field critical currents, nuz decreased to 0.75+/-0.10.
• The distinct exponent values indicate different universality classes for field-tuned transitions with and without dc bias.

Conclusions:

• The superconductor-insulator transition in ultrathin beryllium films is sensitive to the presence of bias current.
• The observed changes in critical exponents suggest that dc bias current drives the system into a different universality class.
• This finding has implications for the fundamental understanding of quantum phase transitions in disordered superconductors.