“…Surface elastic properties of Bi 2 Te 3 were studied at room temperature with the use of a tandem type Brillouin spectrometer (JRS Scientific Instruments), ensuring the contrast of 10 10 53 . A detailed description of the experimental setup can be found in 65 – 68 . The light source used was an Nd:YAG single-mode diode-pumped laser of power 200 mW, emitting the second harmonics of the length λ 0 = 532 nm (Excelsior Spectra Physics).…”
It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
“…Surface elastic properties of Bi 2 Te 3 were studied at room temperature with the use of a tandem type Brillouin spectrometer (JRS Scientific Instruments), ensuring the contrast of 10 10 53 . A detailed description of the experimental setup can be found in 65 – 68 . The light source used was an Nd:YAG single-mode diode-pumped laser of power 200 mW, emitting the second harmonics of the length λ 0 = 532 nm (Excelsior Spectra Physics).…”
It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
“…A detailed description of the experimental setup can be found in Refs. 33 , 34 . Figure 8 Schematic illustration of the sample holder for the surface phonon investigations.…”
High resolution Brillouin spectroscopy was used for the first time to study the dispersion and anisotropy of surface phonons in the single crystal of topological insulator Bi2Te3. Two surface acoustic waves have been observed, which distinguishes this material from other metals or nontransparent materials. The modes were assigned as Rayleigh waves. The obtained results were then simulated by Finite Element Method. The layered structure of the unit cell proposed in simulation reproduced quite well experimental results of the modes dispersion and anisotropy.
“…Furthermore, holey piezoelectric SAW PnCs forming an acoustic cavity for electro‐acoustically generated elastic waves were utilized to realize a one‐port Love SAW resonator operating in the gigahertz . The second strategy consists of PnCs formed by a periodic array of local resonators on a free surface, known also as pillar‐based PnCs, which offer several advantages over holey or inclusion‐based PnCs. Foremost, pillars can work both as periodic scatterers, resulting in Bragg bandgaps, and as local resonators, introducing narrow subwavelength bandgaps .…”
Section: Surface and Membrane Hypersonic 2d Pncsmentioning
confidence: 99%
“…Going further, frequency‐domain BLS proved structure‐induced zone folding and formation of gigahertz Bragg and local resonance acoustic bandgaps for thermally populated SAWs pillar‐based PnCs made out of Si or LiNbO 3. A similar type of PnC was recently utilized for the first experimental realization of a Si‐compatible GHz filter made out in an all‐dielectric platform . The third strategy enabling the modification of SAWs dispersion is based on the nanoparticle–substrate contact resonance.…”
Section: Surface and Membrane Hypersonic 2d Pncsmentioning
confidence: 99%
“…Furthermore, confining the elastic field minimizes losses. Such 2D PnCs have been realized on free surfaces of homogenous or layered media or on thin membranes to gain a control over surface acoustic waves (SAWs) (surface PnCs) [12,[25][26][27]41,[62][63][64][65] or Lamb plate waves (membrane PnCs), [14,35,36,66,67] respectively. In the following, we present different strategies for the modification of the phonon dispersion in PnCs and show resulting phenomena from the viewpoint of the experimental techniques employed for their investigation.…”
Section: Surface and Membrane Hypersonic 2d Pncsmentioning
The central concept in phononics is the tuning of the phonon dispersion relation, or phonon engineering, which provides a means of controlling related properties such as group velocity or phonon interactions and, therefore, phonon propagation, in a wide range of frequencies depending on the geometries and sizes of the materials. Phononics exploits the present state of the art in nanofabrication to tailor dispersion relations in the range of GHz for the control of elastic waves/phonons propagation with applications toward new information technology concepts with phonons as state variable. Moreover, phonons provide an adaptable approach for supporting a coherent coupling between different state variables, and the development of nanoscale optomechanical systems during the last decade attests this prospect. The most extended approach to manipulate the phonon dispersion relation is introducing an artificial periodic modulation of the elastic properties, which is referred to as phononic crystal (PnC). Herein, the focus is on the recent experimental achievements in the fabrication and application of 2D PnCs enabling the modification of the dispersion relation of surface and membrane modes, and presenting phononic bandgaps, waveguiding, and confinement in the hypersonic regime. Furthermore, these artificial materials offer the potential of modifying and controlling the heat flow to enable new schemes in thermal management.
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