Elastic properties and phonon spectra of quasi-two-dimensional VSe2

Gospodarev, I. A.; Eremenko, A. V.; Ignatova, T. V.; Kamarchuk, G. V.; Kolobov, I. G.; Minaev, P. A.; Syrkin, E. S.; Feodosyev, S. B.; Fil, V. D.; Soreau-Leblanc, A.; Molinié, Philippe; Faulques, Eric

doi:10.1063/1.1542414

Cited by 10 publications

(8 citation statements)

References 3 publications

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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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Section: A Stability Of Undistorted Vse2 Layers Withmentioning

confidence: 86%

Section: Monolayer Bilayermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

2017

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“…It has been proposed that the presence of charge density waves could cause the quenching of monolayer ferromagnetism due to the band gap opening induced by Peierls distortion 19 . Phonon spectra of several VSe 2 and similar systems were also considered theoretically 20,21 . This modeling motivates us to study interplay between magnetism and structural phase transitions in VSe 2 .…”

Section: Introductionmentioning

confidence: 99%

Structural phase transitions in VSe₂: energetics, electronic structure and magnetism

Pushkarev

Mazurenko

Boukhvalov

2019

Phys. Chem. Chem. Phys.

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First principles calculations of magnetic and electronic properties of VSe 2 describing the transition between two structural phases (H,T) were performed. Results of the calculations evidence rather low energy barrier ( 0.60 eV for monolayer) for transition between the phases. The energy required for the deviation of Se atom or whole layer of selenium atoms on a small angle up to 10 • from initial positions is also rather low, 0.32 and 0.19 eV/Se, respectively. The changes in band structure of VSe 2 caused by these motions of Se atoms should be taken into account for analysis of the experimental data. Simulations of the strain effects suggest that the experimentally observed T phase of VSe 2 monolayer is the ground state due a substrate-induced strain. Calculations of the difference in total energies of ferromagnetic and antiferromagnetic configurations evidence that the ferromagnetic configuration is the ground state of the system for all stable and intermediate atomic structures. Calculated phonon dispersions suggest visible influence of magnetic configurations on vibrational properties. arXiv:1909.11134v2 [cond-mat.str-el]

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“…This value is close to the previously reported value of 2.67 km/s. [52] In general, defects and imperfect contact can reduce the coherence of acoustic waves and induce different frequencies, which is independent of the material thickness. [49,53] Moreover, as shown in Fig.…”

Section: Interfacial Coherent Acoustic Phonon (Cap) Dynamics In Vbhsmentioning

confidence: 99%

Ultrafast Interfacial Carrier Dynamics and Persistent Topological Surface States in VSe2/Bi2Se3 Van Der Waals Heterojunctions

Park

Jeon

Chun

et al. 2022

Preprint

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Vanadium diselenide (VSe2) has recently been highlighted as an efficient 2D electrode owing to its extra-high conductivity, thickness-controllability, and van der Waals epitaxial contact. However, as the electrode, applications of VSe2 to various material systems are still lacking. Here, by employing ultrafast time-resolved spectroscopy, we study VSe2-thickness-dependent interfacial effects in heterostructures with topological insulator Bi2Se3 that is severely affected by contact with conventional 3D electrodes. Our results particularily show unaltered Dirac surface state of Bi2Se3 against forming junctions with VSe2, efficient ultrafast hot electron transfer from VSe2 to Bi2Se3 across the interface, significantly shortened metastable carrier lifetimes in Bi2Se3 due to dipole interactions enabling efficient current flow, and the electronic level shift (~tens meV) of bulk states of Bi2Se3 caused by interfacial interactions, which is ~10 times lower compared to conventional 3D electrodes, implying weak Fermi level pinning. Our observations confirm VSe2 as an ideal electrode for efficient Bi2Se3-based-applications with full utilization of topological insulator characteristics.

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Elastic properties and phonon spectra of quasi-two-dimensional VSe2

Cited by 10 publications

References 3 publications

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Structural phase transitions in VSe₂: energetics, electronic structure and magnetism

Ultrafast Interfacial Carrier Dynamics and Persistent Topological Surface States in VSe2/Bi2Se3 Van Der Waals Heterojunctions

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Elastic properties and phonon spectra of quasi-two-dimensional VSe2

Cited by 10 publications

References 3 publications

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

Structural phase transitions in VSe2: energetics, electronic structure and magnetism

Ultrafast Interfacial Carrier Dynamics and Persistent Topological Surface States in VSe2/Bi2Se3 Van Der Waals Heterojunctions

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Structural phase transitions in VSe₂: energetics, electronic structure and magnetism