Direct determination of Debye temperature and electron-phonon interaction in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mo>−</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">VSe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Kamarchuk, G. V.; Khotkevich, A. V.; Bagatsky, V. M.; Ivanov, V. G.; Molinié, Philippe; Leblanc, A.; Faulques, Eric

doi:10.1103/physrevb.63.073107

Cited by 22 publications

(10 citation statements)

References 20 publications

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“…While no phonon properties of VS 2 have been reported in the literature, it is possible to infer the electron-phonon coupling constant if we assume the validity of the BCS mean-field theory, 24 as was done for VSe 2 . 25 Using the formula that relates the d band binding energy ⑀ 0 = 0.273 eV ͑at the M point͒ to the CDW transition temperature T CDW = 305 K and , k B T CDW = 1.14⑀ 0 e −1/ , we obtain = 0.42, which is larger than that for VSe 2 , consistent with the higher transition temperature of VS 2 . However, we note two important aspects of our data: ͑1͒ given the momentum dependence of ⑀ 0 we obtain a 20% variation in over the Brillouin-zone points probed, a variation that is caused by the momentum dependence of the electronic structure, not of the phonon properties of VS 2 ; ͑2͒ only the vanadium electrons, in the d 1 configuration, form the Fermi surface of VS 2 , while the sulfur bands lie at higher binding energies.…”

Section: B Electron-phonon Couplingmentioning

confidence: 54%

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

et al. 2010

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We report on the electronic structure and Fermi surfaces of the transition-metal dichalcogenide 1T-VS 2 in the low-temperature charge-density-wave ͑CDW͒ ordered phase. Using soft x-ray angle-resolved photoemission spectroscopy ͑ARPES͒, we investigate the in-plane and out-of-plane vanadium-and sulfur-derived band dispersions and identify k z dispersions in this layered system. Core-level photoemission and x-ray absorption spectroscopy show that vanadium electrons are in the d 1 configuration while 2p-3d resonant ARPES shows only 3d-derived dispersive bands near the Fermi level. Comparison of energy-and angle-dependent data with band-structure calculations reveals renormalization of the 3d bands, but no lower Hubbard band, a signature of the rather weak electron-electron correlations in VS 2 . High-resolution temperature-dependent low-energy ARPES measurements show the opening of an energy gap at the Fermi level that is attributed to the condensation of the CDW phase. The results indicate a CDW transition in the absence of nesting for 1T-VS 2

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Section: B Electron-phonon Couplingmentioning

confidence: 54%

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

et al. 2010

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“…Using mean field theory, we estimated the Curie temperature of the bulk structure to be approximately 39 K and 17 K without a Hubbard-U and with U eff = 1.0 eV, respectively, which is significantly below the charge density transition temperature of 100 -110 K (see Table S1 and the corresponding text in the Supplemental Information). [40][41][42][43][44][45][46] A ferromagnetic ground state is thus not inconsistent with experimental evidence since undistorted 1T-VSe 2 is not stable in the temperature regime in which it would be ferromagnetic.…”

Section: A Stability Of Undistorted Vse2 Layers Withmentioning

confidence: 86%

“…For the 1Tpolytype, T c is predicted to be 35 K for optPBE and U eff = 1.0 eV, and 14 K for optB86b and U eff = 2.5 eV (∆E mag = 11 meV), which is below the experimentally observed charge density wave (CDW) transition temperature of 100 -110 K (onset). [40][41][42][43][44][45][46][52][53][54][55][56] This means that the magnetic transformation in the 1T-structure is unlikely to be observable as the 1T-polytype is unstable at such low temperatures.…”

Section: Monolayer Bilayermentioning

confidence: 99%

“…19,20,22,24,26,[30][31][32][33][34] * davej@uoregon.edu Bulk VSe 2 has been subject to extensive experimental studies due to its ability to intercalate ions [35][36][37][38][39] and its charge density wave (CDW). [40][41][42][43][44][45][46] Few-layer VSe 2 nanosheets were successfully synthesized using liquid exfoliation. 47 These nanosheets retain the CDW and the metallic properties of its bulk analog, but their magnetic properties were reported to be different: the sheets are ferromagnetic at room temperature, whereas bulk VSe 2 exhibits temperature independent paramagnetism.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

2017

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With the emergence of graphene and other two-dimensional (2D) materials, transition metal dichalcogenides have been intensely investigated as potential 2D materials using experimental and theoretical methods. VSe2 is an especially interesting material since its bulk modification exhibits a charge density wave (CDW), the CDW is retained even for few-layer nanosheets, and monolayers of VSe2 are predicted to be ferromagnetic. In this work, we show that electron correlation has a profound effect on the magnetic properties and dynamic stability of VSe2 monolayers and bilayers. Including a Hubbard-U term in the DFT calculations strongly affects the magnetocrystalline anisotropy in the 1T-VSe2 structure, while leaving the 2H-polytype virtually unchanged. This demonstrates the importance of electronic correlations for the electrical and magnetic properties of 1T-VSe2. The Hubbard-U term changes the dynamic stability and the presence of imaginary modes of ferromagnetic 1T-VSe2 while affecting only the amplitudes in the non-magnetic phase. The Fermi surface of non-magnetic of 1T-VSe2 allows for nesting along the CDW vector, but plays no role in ferromagnetic 1T-VSe2. Following the eigenvectors of the soft modes in non-magnetic 1T-VSe2 monolayers yields a CDW structure with a 4×4 supercell and Peierls-type distortion in the atomic positions and electronic structure. The magnetic order indicates the potential for spin density wave structures.

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“…15 The synthesis and characterization of the layered structure of bulk VSe 2 and its superconducting properties have also been investigated experimentally. 16,17 A recent theoretical study on the electronic and magnetic properties of monolayers of VS 2 and VSe 2 18 concluded that the magnetic properties of these structures can be controlled by applying strain.…”

Section: ■ Introductionmentioning

confidence: 99%

Stable, Single-Layer MX₂ Transition-Metal Oxides and Dichalcogenides in a Honeycomb-Like Structure

2012

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Recent studies have revealed that single-layer transition-metal oxides and dichalcogenides (MX 2 ) might offer properties superior to those of graphene. So far, only very few MX 2 compounds have been synthesized as suspended single layers, and some of them have been exfoliated as thin sheets. Using first-principles structure optimization and phonon calculations based on density functional theory, we predict that, out of 88 different combinations of MX 2 compounds, several of them can be stable in free-standing, single-layer honeycomb-like structures. These materials have two-dimensional hexagonal lattices and have top-view appearances as if they consisted of either honeycombs or centered honeycombs. However, their bonding is different from that of graphene; they can be viewed as a positively charged plane of transition-metal atoms sandwiched between two planes of negatively charged oxygen or chalcogen atoms. Electron correlation in transition-metal oxides was treated by including Coulomb repulsion through LDA + U calculations. Our analysis of stability was extended to include in-plane stiffness, as well as ab initio, finite-temperature molecular dynamics calculations. Some of these single-layer structures are direct-or indirect-band-gap semiconductors, only one compound is half-metal, and the rest are either ferromagnetic or nonmagnetic metals. Because of their surface polarity, band gap, high in-plane stiffness, and suitability for functionalization by adatoms or vacancies, these single-layer structures can be utilized in a wide range of technological applications, especially as nanoscale coatings for surfaces contributing crucial functionalities. In particular, the manifold WX 2 heralds exceptional properties promising future nanoscale applications.

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Direct determination of Debye temperature and electron-phonon interaction in1T−VSe2

Cited by 22 publications

References 20 publications

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Stable, Single-Layer MX₂ Transition-Metal Oxides and Dichalcogenides in a Honeycomb-Like Structure

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Direct determination of Debye temperature and electron-phonon interaction in1T−VSe2

Cited by 22 publications

References 20 publications

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

Absence of nesting in the charge-density-wave system1T-VS2as seen by photoelectron spectroscopy

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Stable, Single-Layer MX2 Transition-Metal Oxides and Dichalcogenides in a Honeycomb-Like Structure

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Product

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Stable, Single-Layer MX₂ Transition-Metal Oxides and Dichalcogenides in a Honeycomb-Like Structure