Bandgap Characteristics of a 3D Phononic Meta Material Composed of Ordered Quantum Dots
The authors demonstrated an artificial material composed of ordered semiconductor quantum dots (QDs) with functional acoustic properties. The phononic bandgap of this three-dimensional (3D) artificial crystal was characterized by Raman and transient reflectivity spectroscopies. The Raman spectra exhibited interferometric patterns caused by the coherent interference of acoustic-phononrelated Raman signals, revealing the structural information of the crystal. In addition, the acoustic tunneling in the QD crystal was studied by the transient spectroscopy with the picosecond ultrasonic technique. The measured signals indicated that the QDs are responsible for the scatterings of the acoustic phonons at the bandgap frequency, while the QD crystal serves as a phononic meta material for low-frequency phonons.
KeywordsAcoustic Phonon Optical Pump Coherent Phonon SiGe Alloy Average Sound Velocity
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