Primary Role of the Barely Occupied States in the Charge Density Wave Formation of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>NbSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Shen, Dawei; Zhang, Y.; Yang, Liqiu; Jia, Wei; Ou, H. W.; Dong, J. K.; Xie, B. P.; He, Chi; Zhao, Jun; Zhou, Bo; Arita, Masashi; Shimada, Kenya; Namatame, H.; Takeuchi, Masaki; Shi, Jianping; Feng, D. L.

doi:10.1103/physrevlett.101.226406

Cited by 64 publications

(40 citation statements)

References 28 publications

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“…The calculated electronic band structure is in fairly good agreement with the ab initio band structures obtained by other methods 21,22,[43][44][45][46] and measured in angle-resolved photoemission experiments. [46][47][48][49][50] Some observed differences from the previous calculations performed using other methods are at the same level as the differences among them. We do not expect that this uncertainty in the determination of the band structure could lead to notable effects on the calculated excitation spectra.…”

Section: A Electronic Band Structurementioning

confidence: 73%

Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2H-NbSe2

2012

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We present a study of the electron dynamics in the layered compound 2H -NbSe 2 . First-principles calculations are used to obtain the band structure employed in the evaluation of the loss function with inclusion of local-field (LF) effects. Two different symmetry directions [(100) and (010)] were explored in the hexagonal basal plane. In both cases, a low-energy charge-carrier plasmon (CCP) at ∼1 eV presenting a negative dispersion over a wide momentum transfer range is found, in agreement with recent experimental results [Wezel et al., Phys. Rev. Lett. 107, 176404 (2011)]. On the contrary, in the (001) perpendicular direction, the CCP has negative dispersion at small momenta only, presenting strong positive dispersion at larger momenta. Our calculations reveal that this behavior can be explained without invoking many-body effects, as long as band structure effects are properly included in the evaluation of the excitation spectra. In addition to this CCP mode, we find another one with an arclike oscillating dispersion along the perpendicular direction, as well as the appearance of a CCP replica at high momenta due to LF effects.

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Section: A Electronic Band Structurementioning

confidence: 73%

Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2H-NbSe2

2012

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“…Several independent studies tried to locate the CDW gap using angle-resolved photoemission spectroscopy (ARPES). [5][6][7][8][9] These studies however found either Fermi surface nesting inconsistent with the CDW wave vector or no Fermi surface nesting at all. As such these studies were not conclusive concerning the origin of the charge density wave instability in TMD.…”

Section: Introductionmentioning

confidence: 73%

Anharmonic suppression of charge density waves in 2H-NbS2

et al. 2012

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The temperature dependence of the phonon spectrum in the superconducting transition-metal dichalcogenide 2H-NbS 2 is measured by diffuse and inelastic x-ray scattering. A deep, wide, and strongly temperature-dependent softening of the two lowest-energy longitudinal phonon bands appears along the M symmetry line in reciprocal space. In sharp contrast to the isoelectronic compound 2H-NbSe 2 , the soft phonons energies are finite, even at very low temperature, and no charge density wave instability occurs, in disagreement with harmonic ab initio calculations. We show that 2H-NbS 2 is at the verge of the charge density wave transition and its occurrence is only suppressed by the large anharmonic effects. Moreover, the anharmonicity and the electron phonon coupling both show a strong in-plane anisotropy.

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“…In 2H-NbSe 2 the vector Q ≈ a * /3 is shorter than the radius of the Fermi surface centered at the Γ-point. Changes in DOS at the CDW transition for the three symmetric pairs of points inside the Fermi surface were directly detected in the ARPES experiment [19]. (Actually, in [19] the map of all the spots paired with the Q-vector was obtained for the whole BZ; the pattern has the hexagonal symmetry).…”

Section: A Cdw Instability: Above and Below Tcdwmentioning

confidence: 99%

Strong electron-lattice coupling as the mechanism behind charge density wave transformations in transition-metal dichalcogenides

Gor’kov

2012

Phys. Rev. B

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We consider single band of conduction electrons interacting with displacements of the transitional ions. In the classical regime strong enough coupling transforms the harmonic elastic energy for an ion to the one of the well with two deep minima, so that the system is described in terms of Ising spins. Inter-site interactions order spins at lower temperatures. Extension to the quantum regime is discussed. Below the CDW-transition the energy spectrum of electrons remains metallic because the structural vector Q and the FS sizes are not related. Large values of the CDW gap seen in the tunneling experiments correspond to the energy of the minima in the electron-ion two-well complex. The gap is defined through the density of states (DOS) inside the electronic bands below the CDW transition. We focus mainly on electronic properties of transition-metal dichalcogenides.

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Primary Role of the Barely Occupied States in the Charge Density Wave Formation ofNbSe2

Cited by 64 publications

References 28 publications

Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2H-NbSe2

Role of band structure and local-field effects in the low-energy collective electronic excitation spectra of 2H-NbSe2

Anharmonic suppression of charge density waves in 2H-NbS2

Strong electron-lattice coupling as the mechanism behind charge density wave transformations in transition-metal dichalcogenides

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