Superconductor-insulator transitions in three-dimensional indium-oxide at high pressures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Superconductor-insulator transitions (SIT) are typically studied in 2D systems.
• Existing 2D studies show behaviors inconsistent with theoretical expectations.
• Amorphous indium-oxide (InOx) offers a 3D system to investigate SIT.

Purpose of the Study:

• To investigate the magnetic-field-tuned superconductor-insulator transition (HSIT) in a 3D amorphous indium-oxide (InOx) powder.
• To understand the role of granularity and pressure in controlling the HSIT.
• To characterize the anomalous metallic phases and the nature of the insulating-like state.

Main Methods:

• Utilized a pressure-packed amorphous indium-oxide (InOx) powder.
• Applied hydrostatic pressure up to ~25 GPa.
• Applied magnetic fields to induce and study the HSIT.
• Measured resistivity and critical fields (Hc).

Main Results:

• Observed anomalous metallic phases with high and low resistivity saturations, identified as 'failed insulator' and 'failed superconductor'.
• Superconductivity became robust above ~6 GPa, with critical temperature (Tc) tunable by pressure.
• A quantum critical point was identified at ~25 GPa.
• Magnetic fields induced a HSIT from a superconducting state to a weakly insulating state below Pc.
• The insulating-like state exhibited superconducting character, quenched at higher fields.

Conclusions:

• Granularity in 3D InOx powder plays a crucial role in controlling the HSIT.
• Anomalous metallic phases are manifestations of superconducting fluctuations.
• The 3D system provides a complementary platform to 2D systems for studying HSIT.
• The insulating-like state in the HSIT retains superconducting characteristics.