Weak Dimensionality Dependence and Dominant Role of Ionic Fluctuations in the Charge-Density-Wave Transition of 
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Bianco, Raffaello; Monacelli, Lorenzo; Calandra, Matteo; Mauri, Francesco; Errea, Ion

doi:10.1103/physrevlett.125.106101

Cited by 49 publications

(45 citation statements)

References 55 publications

(68 reference statements)

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“…[ 2 ] In single layer, contradictory results have been reported as ML NbSe 2 on top of Graphene shows a strong increase of T CDW with respect to the bulk, [ 14 ] while ML NbSe 2 grown on top of SiO 2 shows a 3 × 3 CDW with a similar T CDW as in the bulk. Recent first‐principles calculations [ 32 ] confirm the second behavior. It has been shown that electron doping by FET strengthen T CDW , [ 10 ] it is however unclear if a change of ordering vector occurs.…”

Section: Emergence Of 2 × 2 Charge Orderingmentioning

confidence: 78%

“…At a doping of 0.4 electrons/Nb, the region of instability shifts at the M and M ′ points, in qualitative agreement with experimental findings. It is known that [ 32 ] the CDW in NbSe 2 arises from an interplay between Fermi surface effects and ionic fluctuations related to anharmonicity. Fermi surface effects determine the ordering vector, while the occurrence of the CDW is mostly related to phonon–phonon scattering.…”

Section: Emergence Of 2 × 2 Charge Orderingmentioning

confidence: 99%

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Misfit Layer Compounds: A Platform for Heavily Doped 2D Transition Metal Dichalcogenides

Leriche

Palacio-Morales

Campetella

et al. 2020

Adv Funct Materials

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Transition metal dichalcogenides (TMDs) display a rich variety of instabilities such as spin and charge orders, Ising superconductivity, and topological properties. Their physical properties can be controlled by doping in electric double‐layer field‐effect transistors (FET). However, for the case of single layer NbSe2, FET doping is limited to ≈1 × 1014 cm−2, while a somewhat larger charge injection can be obtained via deposition of K atoms. Here, by performing angle‐resolved photoemission spectroscopy, scanning tunneling microscopy, quasiparticle interference measurements, and first‐principles calculations it is shown that a misfit compound formed by sandwiching NbSe2 and LaSe layers behaves as a NbSe2 single layer with a rigid doping of 0.55–0.6 electrons per Nb atom or ≈6 × 1014 cm−2. Due to this huge doping, the 3 × 3 charge density wave is replaced by a 2 × 2 order with very short coherence length. As a tremendous number of different misfit compounds can be obtained by sandwiching TMDs layers with rock salt or other layers, this work paves the way to the exploration of heavily doped 2D TMDs over an unprecedented wide range of doping.

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Section: Emergence Of 2 × 2 Charge Orderingmentioning

confidence: 78%

Section: Emergence Of 2 × 2 Charge Orderingmentioning

confidence: 99%

Misfit Layer Compounds: A Platform for Heavily Doped 2D Transition Metal Dichalcogenides

Leriche

Palacio-Morales

Campetella

et al. 2020

Adv Funct Materials

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“…Finally, recent calculations of the shape of the Kohn anomaly in the transition metal dichalcogenides propose different mechanisms affecting the momentum dependence of its EPC. Among them mode-mode coupling and induced critical fluctuations [12,13], as well as anharmonicity in the soft mode phonon dispersion of 2H-NbSe 2 [41,42] have been proposed. Note that in that respect our hybridization model is a special case of mode-mode coupling theories.…”

Section: Influence Of the Soft Phonon Mode Hybridization In The Momentioning

confidence: 99%

Momentum-dependent electron-phonon coupling in charge density wave systems

2021

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Many charge density wave (CDW) systems exhibit q(T ) electron-hole modulations continuously varying with T and saturating upon cooling at an incommensurate value even if the maximum occurring in the electron-hole Lindhard response does not exhibit such a thermal shift. Using a simple RPA argument we show that the experimental q(T ) can be understood if the electron-phonon coupling (EPC) g(q), necessary to set coupled electronic and structural modulations, is momentum dependent. In this analysis, the sense of variation of q(T ) depends upon the sign of ∂g(q) ∂q and its amplitude of thermal variation is controlled by the electron-hole coherence length (or CDW rigidity) in the modulation direction. This model quantitatively accounts for the thermal dependence of q(T ) in the one-dimensional (1D) CDW system K 0.3 MoO 3 (blue bronze) both in its CDW ground state and in its pretransitional CDW fluctuation regime. We suggest that such a general analysis can be extended to account for the q(T ) dependence observed in other 1D and 2D CDW systems such as the transition metal di-and trichalcogenides as well as the lanthanide and rare-earth tritellurides. Using a detailed analysis of the low frequency phonon spectrum of the blue bronze, we then propose a new scenario for the q dependent EPC, where g(q) is due to a momentum-dependent hybridization between the critical phonon branch bearing the Kohn anomaly and other low-lying phonon branches. This allows obtaining a sign of ∂g(q) ∂q in agreement with that deduced from the analysis of q(T ). Finally, we propose that similar hybridization effects could also be relevant for other 1D and 2D CDW systems exhibiting a thermally dependent modulation.

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“…More recently, the vdW forces holding the two-dimensional layers collectively in NbSe bulk were shown to be the case 2 in which CDW directly related to Fermi surface in the 2H-NbSe structure. To the best of our knowledge, it was well-known that a key factor for the high-T superconductivity depends upon the large Fermi surface topology (FST) size.…”

Section: Introductionmentioning

confidence: 99%

Effect of substitution on the superconducting phase of transition metal dichalcogenide Nb(Se$$_{x}$$S$$_{1-x}$$)$$_{2}$$ van der Waals layered structure

Tsuppayakorn‐aek

Pluengphon

Phansuke

et al. 2021

Sci Rep

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By means of first-principles cluster expansion, anisotropic superconductivity in the transition metal dichalcogenide Nb(Se$$_{x}$$ x S$$_{1-x}$$ 1 - x )$$_{2}$$ 2 forming a van der Waals (vdW) layered structure is observed theoretically. We show that the Nb(Se$$_{0.5}$$ 0.5 S$$_{0.5}$$ 0.5 )$$_{2}$$ 2 vdW-layered structure exhibits minimum ground-state energy. The Pnnm structure is more thermodynamically stable when compared to the 2H–NbSe$$_{2}$$ 2 and 2H–NbS$$_{2}$$ 2 structures. The characteristics of its phonon dispersions confirm its dynamical stability. According to electronic properties, i.e., electronic band structure, density of states, and Fermi surface indicate metallicity of Nb(Se$$_{0.5}$$ 0.5 S$$_{0.5}$$ 0.5 )$$_{2}$$ 2 . The corresponding superconductivity is then investigated through the Eliashberg spectral function, which gives rise to a superconducting transition temperature of 14.5 K. This proposes a remarkable improvement of superconductivity in this transition metal dichalcogenide.

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Weak Dimensionality Dependence and Dominant Role of Ionic Fluctuations in the Charge-Density-Wave Transition of NbSe2

Cited by 49 publications

References 55 publications

Misfit Layer Compounds: A Platform for Heavily Doped 2D Transition Metal Dichalcogenides

Misfit Layer Compounds: A Platform for Heavily Doped 2D Transition Metal Dichalcogenides

Momentum-dependent electron-phonon coupling in charge density wave systems

Effect of substitution on the superconducting phase of transition metal dichalcogenide Nb(Se$$_{x}$$S$$_{1-x}$$)$$_{2}$$ van der Waals layered structure

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