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Low-frequency interlayer phonon dynamics and photoinduced terahertz absorption in black phosphorus
Optics Express
|September 23, 2025
Summary
Terahertz spectroscopy reveals low-frequency interlayer phonon modes in black phosphorus (BP). These modes show temperature-dependent anharmonic coupling and enhanced THz absorption under photoexcitation, crucial for understanding BP
Area of Science:
- Condensed Matter Physics
- Materials Science
- Spectroscopy
Background:
- Black phosphorus (BP) exhibits strong interlayer coupling due to wavefunction overlap, influencing its electronic and optical properties.
- Understanding phonon dynamics is essential for elucidating the complex many-body physics in BP.
Purpose of the Study:
- To investigate the low-frequency interlayer phonon modes in black phosphorus using terahertz (THz) spectroscopy.
- To explore the temperature-dependent behavior and photoexcitation effects on these phonon modes.
Main Methods:
- Steady-state and time-resolved terahertz (THz) spectroscopy were employed to probe phonon dynamics.
- Analysis of THz spectra to identify phonon modes and their coupling behaviors.
Main Results:
- Two distinct low-frequency interlayer phonon modes were identified at 6 and 8.5 meV.
- Anharmonic phonon coupling behavior, indicated by temperature-dependent red shifts, was observed below 150 K.
- Photoexcitation led to significantly increased THz absorption due to enhanced Drude components and phonon oscillator strengths.
Conclusions:
- Interlayer phonon dynamics play a critical role in the electronic and optical properties of black phosphorus.
- The observed anharmonic coupling and non-equilibrium effects provide insights into the many-body physics of BP.
