Superconductor-insulator quantum phase transition in disordered FeSe thin films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Thin Film Physics

Background:

• Epitaxial iron selenium (FeSe) thin films exhibit unique electronic properties.
• Understanding the impact of disorder on superconductivity is crucial for materials science.
• Two-dimensional electronic transport phenomena are key areas of condensed matter research.

Purpose of the Study:

• To investigate the evolution of two-dimensional electronic transport in FeSe thin films as disorder increases.
• To characterize the superconductor-insulator transition (SIT) in these films.
• To determine the nature of the quantum phase transition and its governing mechanisms.

Main Methods:

• Fabrication of epitaxial FeSe thin films with controlled disorder by varying film thickness.
• Measurement of two-dimensional electronic transport properties.
• Finite-size scaling analysis in the critical regime, utilizing the Bose-glass model.
• Tuning the SIT with an applied magnetic field.

Main Results:

• Increasing disorder, induced by reducing film thickness, leads to a superconductor-insulator transition.
• The transition is identified as a continuous quantum phase transition.
• Finite-size scaling analysis supports the Bose-glass model and reveals a critical-exponent product of approximately 7/3.
• The same critical-exponent product is observed when the SIT is tuned by a magnetic field.

Conclusions:

• The superconductor-insulator transition in FeSe thin films is governed by quantum percolation.
• The findings strongly support a continuous quantum phase transition mechanism.
• The study highlights the role of disorder in tuning the electronic properties of FeSe thin films.