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Refractive Index Modulation in Monolayer Molybdenum Diselenide
Melissa Li1, Souvik Biswas1, Claudio U Hail1
1Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States.
Nano Letters
|September 1, 2021
Summary
Monolayer molybdenum diselenide (MoSe2) shows tunable refractive index via Fermi level modulation. This gating enables control over optical properties, paving the way for advanced photonics applications.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Optoelectronics
Background:
- Two-dimensional transition metal dichalcogenides exhibit tunable excitonic resonances.
- Monolayer molybdenum diselenide (MoSe2) shows promise for light modulation.
- Previous studies focused on reflectivity, not permittivity or index modulation.
Purpose of the Study:
- Investigate gate-tunability of complex refractive index in monolayer MoSe2.
- Study doping dependence of excitonic resonances (A and B) from 4 to 150 K.
- Explore epsilon-near-zero response and metallic-to-dielectric transitions.
Main Methods:
- Fermi level modulation via electrostatic gating.
- Cryogenic temperature measurements (4–150 K).
- Analysis of excitonic resonances and complex refractive index.
Main Results:
- Demonstrated large gate-tunability of complex refractive index in monolayer MoSe2.
- Observed temperature- and carrier-dependent epsilon-near-zero permittivity.
- Showcased a transition from metallic to dielectric behavior near the A exciton energy.
- Attributed refractive index control to tunable radiative and non-radiative decay channels.
Conclusions:
- Monolayer MoSe2 offers dynamic control over its refractive index.
- The material shows potential for emerging photonics applications.
- Gating-induced modulation of excitonic properties is key to optical control.
