Coherent optical phonons in a Bi2Se3 single crystal measured via transient anisotropic reflectivity

Norimatsu, Katsura; Hu, Jianbo; Goto, Atsuko; Igarashi, Kyushiro; Sasagawa, T.; Nakamura, Kazutaka G.

doi:10.1016/j.ssc.2012.12.023

Cited by 24 publications

(26 citation statements)

References 31 publications

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“…The ratios of decay rate to mode frequency, i.e., Fano factor [24] for both modes, are almost the same. Note that a similar observation has been reported for coherent phonons in Bi 2 Se 3 [25,26], however, initial amplitudes of the coherent modes obtained by anisotropic detection, i.e., the subtraction of two orthogonal components of the reflected linear polarized light, were reported to be almost equal.…”

Section: Resultssupporting

confidence: 83%

“…As a result, no fully symmetric mode with equal diagonal elements can be detected by anisotropic detection; however, the amplitude of fully symmetric phonons in Ref. [26] was comparable with that of E (II) g mode. This can be due to either unbalanced photodiodes, or coupling to the "b" component of the A 1g Raman tensor and excludes the possibility to compare polarizabilities of the modes correctly from the anisotropic transient reflectivity alone.…”

Section: Resultsmentioning

confidence: 87%

“…We have to stress here that the generation of lowsymmetry coherent phonons in Bi 2 Te 3 is suppressed but not prohibited. Indeed, it is appropriate to mention that in Bi 2 Se 3 and Sb 2 Te 3 topological insulators, which are isomorphic to Bi 2 Te 3 , both E (I) g and E (II) g modes have been detected [25,26,33] using anisotropic detection scheme. To access the anisotropic reflectivity change, after reflecting from the sample, the probe beam is analyzed into polarization components parallel and perpendicular to that of the pump, R || and R ⊥ , and their difference is recorded with two balanced photodiodes.…”

Section: Resultsmentioning

confidence: 99%

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Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

2015

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We have studied the polarization dependence of coherent phonons in the topological insulator Bi 2 Te 3 . Using polarization-dependent femtosecond pump-probe spectroscopy, we measured coherent phonons as a function of angle when the pump and probe polarizations were fixed, and the crystal orientation was rotated. For isotropic detection, depending on the spot position, oscillations either from only low-and high-frequency phonons of A 1g symmetry, or in addition from the mode at 3.6 THz were observed. All the modes were found to be independent of the orientation of electric field vector with respect to the crystal axes testifying to their full symmetry while no modes of lower symmetry appeared in any polarization geometry. For anisotropic detection both modes of E g symmetry could be detected, but their amplitudes were considerably smaller than those of A 1g symmetry. To clarify the coherent phonon assignment and the process of coherent phonon generation in Bi 2 Te 3 , the time-domain measurements were complemented by spontaneous Raman scattering. The comparison of frequency-and time-domain results and the polarization dependence suggest that the 3.6 THz mode belongs to crystalline Te arising due to tellurium segregation. A discrepancy between the time-and frequency-domain data is discussed.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

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Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

2015

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“…Coherent phonons are widely used to study phonon dynamics for a wide variety of materials such as semimetals, [1][2][3][4][5] semiconductors, [6][7][8][9][10][11][12][13] superconductors, [14][15][16][17] and topological insulators, [18][19][20][21] with pump-probe type time-resolved reflectivity measurements. An ultrashort pump pulse coherently excites optical phonons which oscillate in phase and modulate the electric susceptibility.…”

Section: Introductionmentioning

confidence: 99%

“…Also, several experiments showed that the phonon oscillation often shifted from the sine or cosine oscillations and its phase was dependent on the materials and phonon modes. 4,20,30 Thus, the generation mechanism for coherent phonons is still controversial, especially for the opaque region where both the light absorption and Raman processes coexist.…”

Section: Introductionmentioning

confidence: 99%

Influence of pulse width and detuning on coherent phonon generation

2015

Self Cite

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We investigated the coherent phonon generation mechanism by irradiation of an ultrashort pulse with a simple two-level model. Our derived formulation shows that both impulsive stimulated Raman scattering (ISRS) and impulsive absorption (IA) simultaneously occur and phonon wave packets are generated in the electronic ground and excited states by ISRS and IA, respectively. We identify the dominant process from the amplitude of the phonon oscillation. For short pulse widths, the ISRS is very small and becomes larger as the pulse width increases. We also show that the initial phase is dependent on the pulse width and the detuning.

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Revealing the Substrate Dependent Ultrafast Phonon Dynamics in Bi₂Se₃ Thin Films

Saini

Tailor

Sharma

et al. 2022

Adv Materials Inter

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The bulk carrier excitation influences the phonon dynamics, which can alter and modulate the surface charge density of topological insulators such as bismuth selenide (Bi2Se3). This work investigates the charge carrier and phonon dynamics in Bi2Se3 grown on various substrates. The orientation of the substrate, the size of the crystallites, and the misfit of the lattice affect the carrier and phonon dynamics. Bi2Se3 thin films are grown under the same growth conditions on SiO2, Si(111), and SiN. Bi2Se3 overlayers exhibit substrate‐dependent charge carrier relaxation channels and phonon dynamics. It is evident from Raman spectroscopy and ultrafast transient absorption spectroscopy that the heterointerface interactions of all three samples affect the vibration modes of Bi2Se3 and coherent acoustic phonon oscillations in the NIR range. At 13.6, 41.2, and 34.4 GHz, the vibration modes of SiO2, Si(111), and SiN are equivalent. The propagation depth of phonon waves is shown by measuring the speed of sound in Bi2Se3 overlayers on SiO2, Si(111), and SiN. This study demonstrates that the surface and bulk‐bound charge carriers of a topological insulator determine the frequency and velocity of the generated sound.

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Coherent optical phonons in a Bi2Se3 single crystal measured via transient anisotropic reflectivity

Cited by 24 publications

References 31 publications

Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

Influence of pulse width and detuning on coherent phonon generation

Revealing the Substrate Dependent Ultrafast Phonon Dynamics in Bi₂Se₃ Thin Films

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Coherent optical phonons in a Bi2Se3 single crystal measured via transient anisotropic reflectivity

Cited by 24 publications

References 31 publications

Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

Polarization dependence of coherent phonon generation and detection in the three-dimensional topological insulatorBi2Te3

Influence of pulse width and detuning on coherent phonon generation

Revealing the Substrate Dependent Ultrafast Phonon Dynamics in Bi2Se3 Thin Films

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Product

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Revealing the Substrate Dependent Ultrafast Phonon Dynamics in Bi₂Se₃ Thin Films