Comparison of the soft modes in tantalum dichalcogenides

Sugai, S.; Murase, K.; Uchida, S.; Tanaka, Shōji

doi:10.1016/0378-4363(81)90284-9

Cited by 45 publications

(57 citation statements)

References 13 publications

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“…Below 90 K, four new Raman modes appear at energy range lower than 85 cm −1 in Raman spectrum which are directly associated with the creation of the CDW superlattice over underlying crystal lattice45. However, in our measurements, we could not observe these peaks and the rigid-layer mode, because our Rayleigh rejection filter has a cut-off point above 80 cm −1 .…”

Section: Resultscontrasting

confidence: 55%

Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe2

Hajiyev

Cong

Qiu

et al. 2013

Sci Rep

133

126

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In this article, we report the first successful preparation of single- and few-layers of tantalum diselenide (2H-TaSe2) by mechanical exfoliation technique. Number of layers is confirmed by white light contrast spectroscopy and atomic force microscopy (AFM). Vibrational properties of the atomically thin layers of 2H-TaSe2 are characterized by micro-Raman spectroscopy. Room temperature Raman measurements demonstrate MoS2-like spectral features, which are reliable for thickness determination. E1g mode, usually forbidden in backscattering Raman configuration is observed in the supported TaSe2 layers while disappears in the suspended layers, suggesting that this mode may be enabled because of the symmetry breaking induced by the interaction with the substrate. A systematic in-situ low temperature Raman study, for the first time, reveals the existence of incommensurate charge density wave phase transition in single and double-layered 2H-TaSe2 as reflected by a sudden softening of the second-order broad Raman mode resulted from the strong electron-phonon coupling (Kohn anomaly).

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Section: Resultscontrasting

confidence: 55%

Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe2

Hajiyev

Cong

Qiu

et al. 2013

Sci Rep

133

126

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“…A Fourier transform of the time traces at this temperature, shown in Fig. 1(h), reveals the presence of coherent modes at 2.4 THz and 3.8 THz, corresponding to the CDW amplitude mode and an additional totally symmetric phonon mode, respectively [28][29][30] . The slow-rising 2.1 THz mode that has been observed in single-wavelength pump-probe experiments 30 is present in the data as well, but is merged in the Fourier transform with the amplitude mode peak.…”

Section: A Temperature Dependencementioning

confidence: 94%

Probing the coupling between a doublon excitation and the charge-density wave inTaS2by ultrafast optical spectroscopy

et al. 2016

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Recently, the switching between the different charge-ordered phases of 1T -TaS 2 has been probed by ultrafast techniques, revealing unexpected phenomena such as "hidden" metastable states and peculiar photoexcited charge patterns. Here, we apply broadband pump-probe spectroscopy with varying excitation energy to study the ultrafast optical properties of 1T -TaS 2 in the visible regime.By scanning the excitation energy in the near-IR region we unravel the coupling between different charge excitations and the low-lying charge-density wave state. We find that the amplitude mode of the charge-density wave exhibits strong coupling to a long-lived doublon state that is photoinduced in the center of the star-shaped charge-ordered Ta clusters by the near-IR optical excitation.

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“…In earlier work on bulk 1T-TaS2 [21], modes B1 and B2 were identified as C phase acoustic phonon modes arising primarily from the vibration of Ta atoms. While one may expect such a mode to soften in thin samples as interlayer interactions disappear, the growth in intensity of secondary surface modes that are separately resolved from the bulk modes is unique.…”

mentioning

confidence: 98%

Distinct surface and bulk charge density waves in ultrathin 1T−TaS2

Okamoto

et al. 2016

Phys. Rev. B

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We employ low-frequency Raman spectroscopy to study the nearly commensurate (NC) to commensurate (C) charge density wave (CDW) transition in 1T-TaS2 ultrathin flakes protected from oxidation. We identify new modes originating from C phase CDW phonons that are distinct from those seen in bulk 1T-TaS2. We attribute these to CDW modes from the surface layers. By monitoring individual modes with temperature, we find that surfaces undergo a separate, low-hysteresis NC-C phase transition that is decoupled from the transition in the bulk layers. This indicates the activation of a secondary phase nucleation process in the limit of weak interlayer interaction, which can be understood from energy considerations.

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Comparison of the soft modes in tantalum dichalcogenides

Cited by 45 publications

References 13 publications

Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe2

Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe2

Probing the coupling between a doublon excitation and the charge-density wave inTaS2by ultrafast optical spectroscopy

Distinct surface and bulk charge density waves in ultrathin 1T−TaS2

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