Metal to Insulator Quantum-Phase Transition in Few-Layered ReS₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Rhenium disulfide (ReS2) possesses a direct band gap suitable for optoelectronics.
• The 1T'-structure of ReS2 leads to anisotropic properties and potential non-trivial topology.
• Understanding the electronic behavior of few-layered ReS2 is crucial for device applications.

Purpose of the Study:

• To investigate the anisotropic Raman response and transport properties of few-layered ReS2 field-effect transistors.
• To elucidate the mechanism behind the electric-field induced metallic state in ReS2.
• To explore the potential of ReS2 for electronic device applications.

Main Methods:

• Exfoliation of few-layered ReS2 on SiO2.
• Fabrication and characterization of ReS2 field-effect transistors.
• Measurement of anisotropic Raman response and transport properties (resistivity, conductivity) as a function of temperature and electron density.
• Scaling analysis of conductivity.

Main Results:

• ReS2 behaves as an n-type semiconductor with increasing carrier mobility at lower temperatures.
• At high electron densities, ReS2 exhibits a metallic T(2)-dependence upon cooling.
• The electric-field induced metallic state in ReS2 arises from a second-order metal-to-insulator transition driven by electronic correlations.

Conclusions:

• The electronic band structure of 1T'-ReS2 is sensitive to perpendicular electric fields.
• The observed metallic state is attributed to electronic correlations, differing from percolation mechanisms.
• The gate-induced metallic state in ReS2 provides a pathway for creating ohmic contacts and metallic interconnects in transition metal dichalcogenide devices.