Experimental evidence for a collective insulating state in two-dimensional superconductors

Area of Science:

• Condensed matter physics
• Materials science
• Superconductivity

Background:

• Disordered thin films exhibit complex electronic properties under external stimuli.
• Superconductivity is sensitive to magnetic fields, often degrading with increasing field strength.
• Understanding the transition from superconducting to insulating states is crucial for novel electronic applications.

Purpose of the Study:

• To experimentally investigate the current-voltage characteristics of amorphous indium oxide thin films in strong magnetic fields.
• To determine the critical magnetic field (B(c)) at which superconductivity is suppressed.
• To explore the nature of the insulating state and its conduction properties at low temperatures.

Main Methods:

• Fabrication of disordered, superconducting, thin films of amorphous indium oxide.
• Measurement of current-voltage characteristics under varying magnetic field strengths (B).
• Differential conductance measurements in the insulating phase as a function of temperature.

Main Results:

• Superconductivity in the films degrades with increasing magnetic field strength.
• A critical magnetic field (B(c)) was identified, beyond which the films transition to an insulating state.
• Differential conductance in the insulating phase abruptly vanished below a specific temperature, revealing a conduction threshold.

Conclusions:

• A new collective state emerges in two-dimensional superconductors subjected to strong magnetic fields.
• The observed conduction threshold in the insulating phase provides evidence for distinct electronic ordering.
• These findings contribute to the fundamental understanding of quantum phase transitions in disordered superconductors.