Low-Temperature 2D/2D Ohmic Contacts in WSe₂ Field-Effect Transistors as a Platform for the 2D Metal-Insulator...

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Two-dimensional (2D) materials like tungsten diselenide (WSe2) exhibit unique electronic properties.
• Understanding the metal-insulator transition in 2D systems is crucial for fundamental physics and device applications.
• High-quality encapsulation and contacts are essential for accurate measurements of 2D electronic phenomena.

Purpose of the Study:

• To fabricate and characterize hexagonal boron nitride (hBN)-encapsulated WSe2 Hall bars for studying the 2D metal-insulator transition.
• To investigate the temperature and carrier density dependence of conductivity in WSe2 devices.
• To explore the role of electron-electron interactions and disorder in quantum phase transitions within 2D materials.

Main Methods:

• Fabrication of multiterminal WSe2 Hall bars encapsulated with hexagonal boron nitride (hBN).
• Development of 2D/2D low-temperature Ohmic contacts for precise electrical measurements.
• Characterization of device conductivity (σ) as a function of temperature (T) and carrier density (ns) down to 0.25 K.

Main Results:

• Demonstrated Ohmic behavior in WSe2 devices at temperatures as low as 0.25 K, minimizing current-heating effects.
• Achieved accurate carrier density determination due to high-quality hBN encapsulation and ideal Hall-bar geometry.
• Observed conductivity scaling behavior consistent with a quantum phase transition driven by electron-electron interactions and disorder-induced magnetic moments.

Conclusions:

• The fabricated hBN-encapsulated WSe2 platform is suitable for investigating 2D metal-insulator transitions.
• Findings suggest a quantum phase transition influenced by both electron interactions and disorder.
• The contact engineering approach provides a pathway for future studies on 2D transition metal dichalcogenides.