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Dramatic Plasmon Response to the Charge-Density-Wave Gap Development in 1T-TiSe_{2}.
Zijian Lin1,2, Cuixiang Wang1,2, A Balassis3
1Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Physical Review Letters
|November 14, 2022
Summary
1T-TiSe2 exhibits charge density wave (CDW) properties. This study reveals plasmon damping mechanisms, challenging exciton insulator theories and highlighting plasmon tunability in CDW materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- 1T-TiSe2 is a prominent charge density wave (CDW) material.
- It is considered a candidate for exciton insulator behavior, suggested by plasmon softening.
- Understanding its electronic properties is key to exploring novel quantum phenomena.
Purpose of the Study:
- To investigate the temperature-dependent plasmon behavior in 1T-TiSe2.
- To clarify the role of plasmons in the CDW transition and exciton condensation.
- To determine the damping mechanisms of plasmons in this material.
Main Methods:
- High-resolution electron energy loss spectroscopy (HREELS).
- Systematic temperature-dependent measurements.
- Analysis of plasmon and phonon modes.
Main Results:
- Plasmon and phonon modes were clearly resolved.
- Landau damping of plasmons at finite momentums was observed, refuting plasmon softening for exciton condensation.
- Plasmon lifetime at zero momentum showed strong correlation with band gap evolution during the CDW transition.
- Interband transitions near the Fermi level act as a significant plasmon damping channel in the normal phase, suppressed in the CDW phase.
Conclusions:
- The findings do not support the exciton condensation picture based on plasmon softening in 1T-TiSe2.
- Plasmon damping is strongly influenced by the opening of the CDW gap.
- This work reveals significant tunability of plasmons in semimetals and small-gap semiconductors like 1T-TiSe2.
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