Excitonic instability in transition metal dichalcogenides.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Transition-metal dichalcogenide (TMDC) monolayers are 2D materials with unique electronic properties.
• Lack of inversion symmetry in TMDCs, caused by factors like substrate presence or electric fields, leads to phenomena like tilted massive Dirac Hamiltonians.
• Janus materials are a specific class of TMDCs that lack inversion symmetry.

Purpose of the Study:

• To investigate the properties of excitons in TMDC monolayers that lack inversion symmetry.
• To explore the potential of these materials for hosting the exciton insulator phase.
• To analyze the excitonic contribution to optical conductivity and associated selection rules.

Main Methods:

• Theoretical exploration of exciton properties in non-centrosymmetric TMDC monolayers.
• Analysis of exciton binding energies relative to the electronic band gap.
• Investigation of optical conductivity and selection rules influenced by excitonic effects.

Main Results:

• Exciton binding energies in these materials can exceed the electronic band gap.
• This suggests TMDC monolayers lacking inversion symmetry are promising for the exciton insulator phase.
• The study analyzes the impact of excitons on optical conductivity and selection rules.

Conclusions:

• TMDC monolayers lacking inversion symmetry possess unique exciton characteristics.
• Their potential for the exciton insulator phase is significant due to high exciton binding energies.
• Understanding these excitonic properties is crucial for future optoelectronic applications.