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Wave transport in random media: the ballistic to diffusive transition
Z Q Zhang1, I P Jones, H P Schriemer
1Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Summary
Wave transport in scattering media transitions from ballistic to diffusive behavior. This study reveals an abrupt crossover around three mean free paths, validated by theory and ultrasonic experiments.
Area of Science:
- Wave physics
- Condensed matter physics
- Acoustics
Background:
- Understanding wave transport through scattering media is crucial for various applications.
- Distinguishing between ballistic and diffusive transport is key to characterizing wave propagation.
- Previous models often struggle to accurately describe the transition in thin samples.
Purpose of the Study:
- To investigate wave transport characteristics in a strongly scattering medium.
- To analyze the transition from ballistic to diffusive behavior as a function of sample thickness.
- To compare theoretical predictions with experimental data.
Main Methods:
- First-principles calculation of frequency correlation and time-domain intensity.
- Experimental investigation using an ultrasonic technique.
- Separation of ballistic and scattered wave components.
Main Results:
- Good agreement between theory, diffusion approximation, and experiment for thicknesses > 4 mean free paths.
- Systematic differences observed in thinner samples.
- Abrupt crossover in scattered peak arrival time at L/l ≈ 3, marking the transition.
Conclusions:
- The study successfully characterizes the transition from ballistic to diffusive wave transport.
- A crossover point around three mean free paths is identified and validated.
- The developed theoretical framework and experimental method provide accurate descriptions of wave transport across various sample thicknesses.