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Structural, electronic and vibrational properties of few-layer 2H- and 1T-TaSe2.

Yan JA, Cruz MA, Cook B, Varga K - Sci Rep (2015)

Bottom Line: We present first- principles calculations of structural phase energetics, band dispersion near the Fermi level, phonon properties and vibrational modes at the Brillouin zone center for different layer numbers, crystal phases and stacking geometries.Evolution of the Fermi surfaces as well as the phonon dispersions as a function of layer number reveals dramatic dimensionality effects in this CDW material.Our results indicate strong electronic interlayer coupling, detail energetically possible stacking geometries, and provide a basis for interpretation of Raman spectra.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Astronomy, and Geosciences, Towson University, 8000 York Road, Towson, Md 21252, USA.

ABSTRACT
Two-dimensional metallic transition metal dichalcogenides (TMDs) are of interest for studying phenomena such as charge-density wave (CDW) and superconductivity. Few-layer tantalum diselenides (TaSe2) are typical metallic TMDs exhibiting rich CDW phase transitions. However, a description of the structural, electronic and vibrational properties for different crystal phases and stacking configurations, essential for interpretation of experiments, is lacking. We present first- principles calculations of structural phase energetics, band dispersion near the Fermi level, phonon properties and vibrational modes at the Brillouin zone center for different layer numbers, crystal phases and stacking geometries. Evolution of the Fermi surfaces as well as the phonon dispersions as a function of layer number reveals dramatic dimensionality effects in this CDW material. Our results indicate strong electronic interlayer coupling, detail energetically possible stacking geometries, and provide a basis for interpretation of Raman spectra.

No MeSH data available.


Related in: MedlinePlus

Fermi surface for few-layer 2H-TaSe2 and 1T-TaSe2 as a function of layer number with SOC explicitly included.
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f6: Fermi surface for few-layer 2H-TaSe2 and 1T-TaSe2 as a function of layer number with SOC explicitly included.

Mentions: The evolutions of the Fermi surface topology as a function of layer number for both 2H and 1T phases are presented in Fig. 6, with SOC explicitly included. Overall, the Fermi surfaces of few-layer TaSe2 mimic their bulk. There is, however, a sharp change on the Fermi surface from monolayer to bilayer for both 2H and 1T phases. Specifically, the Fermi contours centered at M point evolve from 2H-1L (Fig. 6(a)) to 2H-2L (Fig. 6(c)), which begins to center at K point. From 1T-1L to 1T-2L, additional Fermi surface sheets show up at the BZ corner (K point), as depicted in Fig. 6(b,d). In addition, small Fermi surface sheets appear at around Γ in 1T-2L. Clearly, with reduced dimensions, the Fermi surface shows distinct topology from that in the bulk and thus is sensitive to the layer number as well as stacking geometry.


Structural, electronic and vibrational properties of few-layer 2H- and 1T-TaSe2.

Yan JA, Cruz MA, Cook B, Varga K - Sci Rep (2015)

Fermi surface for few-layer 2H-TaSe2 and 1T-TaSe2 as a function of layer number with SOC explicitly included.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644971&req=5

f6: Fermi surface for few-layer 2H-TaSe2 and 1T-TaSe2 as a function of layer number with SOC explicitly included.
Mentions: The evolutions of the Fermi surface topology as a function of layer number for both 2H and 1T phases are presented in Fig. 6, with SOC explicitly included. Overall, the Fermi surfaces of few-layer TaSe2 mimic their bulk. There is, however, a sharp change on the Fermi surface from monolayer to bilayer for both 2H and 1T phases. Specifically, the Fermi contours centered at M point evolve from 2H-1L (Fig. 6(a)) to 2H-2L (Fig. 6(c)), which begins to center at K point. From 1T-1L to 1T-2L, additional Fermi surface sheets show up at the BZ corner (K point), as depicted in Fig. 6(b,d). In addition, small Fermi surface sheets appear at around Γ in 1T-2L. Clearly, with reduced dimensions, the Fermi surface shows distinct topology from that in the bulk and thus is sensitive to the layer number as well as stacking geometry.

Bottom Line: We present first- principles calculations of structural phase energetics, band dispersion near the Fermi level, phonon properties and vibrational modes at the Brillouin zone center for different layer numbers, crystal phases and stacking geometries.Evolution of the Fermi surfaces as well as the phonon dispersions as a function of layer number reveals dramatic dimensionality effects in this CDW material.Our results indicate strong electronic interlayer coupling, detail energetically possible stacking geometries, and provide a basis for interpretation of Raman spectra.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Astronomy, and Geosciences, Towson University, 8000 York Road, Towson, Md 21252, USA.

ABSTRACT
Two-dimensional metallic transition metal dichalcogenides (TMDs) are of interest for studying phenomena such as charge-density wave (CDW) and superconductivity. Few-layer tantalum diselenides (TaSe2) are typical metallic TMDs exhibiting rich CDW phase transitions. However, a description of the structural, electronic and vibrational properties for different crystal phases and stacking configurations, essential for interpretation of experiments, is lacking. We present first- principles calculations of structural phase energetics, band dispersion near the Fermi level, phonon properties and vibrational modes at the Brillouin zone center for different layer numbers, crystal phases and stacking geometries. Evolution of the Fermi surfaces as well as the phonon dispersions as a function of layer number reveals dramatic dimensionality effects in this CDW material. Our results indicate strong electronic interlayer coupling, detail energetically possible stacking geometries, and provide a basis for interpretation of Raman spectra.

No MeSH data available.


Related in: MedlinePlus