Vertical Quantum Confinement in Bulk MoS₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Quantum confinement effects are typically studied in lower-dimensional materials.
• Bulk materials offer unique platforms for exploring quantum phenomena when confinement is induced.

Purpose of the Study:

• To experimentally observe and characterize quantum confinement states in bulk molybdenum disulfide (MoS2).
• To investigate the nature of quantum well states (QWSs) and their energy dependence in bulk MoS2.
• To understand the role of preparation methods in inducing quantum confinement.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was used to probe the electronic band structure.
• Density functional theory (DFT) calculations were employed to support experimental observations.

Main Results:

• Quantum well states (QWSs) resulting from vertical quantum confinement were observed at the Γ̅ point of bulk MoS2.
• The binding energy of QWSs exhibited a linear dependence on the quantum number (n), deviating from the quadratic behavior of 2DEGs.
• Mechanical exfoliation was identified as the preparation method leading to the observed confinement.

Conclusions:

• Bulk MoS2 can exhibit quantum confinement effects, leading to observable quantum well states.
• The linear energy-binding energy relationship suggests a parabolic-like quantum well potential.
• This discovery opens possibilities for studying intersubband transitions and fundamental quantum phenomena in multilayer MoS2 stacks.