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Gate-Controlled Terahertz Modulation in Graphene-Integrated Bi2Se3 Microstructure
Chihun In1,2, Sumin Lee3,4, Deepti Jain5
1Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany.
Nano Letters
|December 9, 2025
Summary
Terahertz spectroscopy reveals how graphene influences Bi2Se3 Dirac plasmon polaritons. Large graphene polarizability allows significant control over this coupled mode using moderate gate voltages.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Spectroscopy
Background:
- Terahertz (THz) spectroscopy probes collective oscillations of free charge carriers in 2D materials.
- The resonant response in THz spectra is linked to 2D plasmon modes.
Purpose of the Study:
- Investigate the spectral extinction of THz waves transmitted through graphene-integrated Bi2Se3 microstructures.
- Characterize the control of Bi2Se3 Dirac plasmon polaritons (DPPs) by graphene via gate voltage.
Main Methods:
- Utilized THz spectroscopy to measure spectral extinction.
- Employed electromagnetic wave simulations to analyze the coupled plasmon modes.
- Varied bias voltage to control sheet conductance and particle density.
Main Results:
- Observed consistent spectral modulation with varying particle density, matching simulation results.
- Characterized the coupling between Bi2Se3 DPPs and graphene.
- Demonstrated up to 70% control of the Bi2Se3 DPP mode using a -1 to 1 V gate voltage range due to large graphene polarizability.
Conclusions:
- Graphene's polarizability significantly influences Bi2Se3 DPPs.
- Provides insights into interlayer long-range Coulomb interactions in Dirac materials.
- Highlights potential for gate-tunable THz devices based on coupled Dirac materials.
