Charge density wave transition in single-layer titanium diselenide

Chen, Peng-Jen; Chan, Yang-Hao; Fang, Xing; Zhang, Yi; Chou, M. Y.; Hussain, Zahid; Fedorov, A. V.; Chiang, T.‐C.

doi:10.1038/ncomms9943

Cited by 241 publications

(275 citation statements)

References 28 publications

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“…This is a feature common to the entire class of LTMD materials [47,48]. A similar CDW phase transition has been observed experientially in TiSe 2 , a compound iso-structural and isoelectronic to TiS 2 , with transition temperatures reported to be as large as 200 K and 232 K, respectively for bulk and monolayers [49]. The experimental evidence for the CDW phase was explained with an excitonic mechanism without invoking FS nesting and Jahn-Teller distorsion [50,51].…”

Section: (B)supporting

confidence: 73%

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂

Dolui¹,

Sanvito²

2016

EPL

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Density functional theory and density functional perturbation theory are used to investigate the electronic and vibrational properties of TiS2. Within the local density approximation the material is a semimetal both in the bulk and in the monolayer form. Most interestingly we observe a Kohn anomaly in the bulk phonon dispersion, which turns into a charge density wave instability when TiS2 is thinned to less than four monolayers. Such instability, however, disappears when one calculates the electronic structure with a functional, such as the LDA+U, which returns an insulating ground state. In this situation charge-doping or strain does not bring back the charge density wave instability, whereas the formation of the TiSSe alloy does.

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Section: (B)supporting

confidence: 73%

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂

Dolui¹,

Sanvito²

2016

EPL

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“…However, upon further cooling the resistivity reaches an anomalous maximum [7], after which a weak metallic behavior is observed. By contrast, ARPES finds an insulating low-T phase, with a gap of approximately 0.15 eV [9][10][11][12][13][14]. In the high-T phase ARPES has not been able to conclude whether the system is semimetallic or semiconducting due to the very small indirect (possibly negative) gap.…”

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confidence: 93%

Critical Role of the Exchange Interaction for the Electronic Structure and Charge-Density-Wave Formation in TiSe2

et al. 2017

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We show that the inclusion of screened exchange via hybrid functionals provides a unified description of the electronic and vibrational properties of TiSe 2 . In contrast to local approximations in density functional theory, the explicit inclusion of exact, nonlocal exchange captures the effects of the electron-electron interaction needed to both separate the Ti-d states from the Se-p states and stabilize the charge-densitywave (CDW) (or low-T) phase through the formation of a p-d hybridized state. We further show that this leads to an enhanced electron-phonon coupling that can drive the transition even if a small gap opens in the high-T phase. Finally, we demonstrate that the hybrid functionals can generate a CDW phase where the electronic bands, the geometry, and the phonon frequencies are in agreement with experiments. DOI: 10.1103/PhysRevLett.119.176401 The charge density wave (CDW) instability is a common phenomenon in layered semimetallic transition metal dichalcogenides (TMDs) [1] and has attracted considerable interest over the years, from both the experimental and the theoretical side. The CDW phase is often found to compete with superconductivity and thus plays a similar role as the antiferromagnetic phase in strongly correlated heavy fermion systems or in high-T c cuprates [2][3][4][5]. This intriguing similarity has stimulated the search for a better understanding of the physical mechanism behind the CDW instability in TMDs [6].The CDW instability in TiSe 2 is one of the most studied and debated. On the experimental side, neutron diffraction [7] and x-ray scattering [8] have established the existence of a commensurate 2 × 2 × 2 structural transition at 200 K. This is confirmed by angle resolved photo emission spectroscopy (ARPES) as well as by transport measurements [7], where an abrupt increase in resistivity is found at the same temperature. However, upon further cooling the resistivity reaches an anomalous maximum [7], after which a weak metallic behavior is observed. By contrast, ARPES finds an insulating low-T phase, with a gap of approximately 0.15 eV [9][10][11][12][13][14]. In the high-T phase ARPES has not been able to conclude whether the system is semimetallic or semiconducting due to the very small indirect (possibly negative) gap. Theoretically, this fact makes TiSe 2 an ideal candidate to exhibit an excitonic insulator phase [9,[15][16][17] for which the CDW transition is driven by a purely electronic instability. Some recent experiments [18] partly support this scenario. On the other hand, excitonic correlations alone are insufficient as demonstrated in Ref. [19].Additional experimental evidence for the CDW instability has been provided by vibrational spectra as a function of temperature. A complete softening of an optical phonon at the L point has been observed in inelastic x-ray scattering experiments [20]. In Raman and infrared (IR) spectroscopy the transition is detected by the appearance of a large number of new modes [21,22], some of which can be related to the CDW transition ...

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“…Moreover, the substrate screening also changes the nature of Coulomb interactions in graphene on top of either dielectric materials or metals and hence modifies the bands further 13,18 . Besides graphene, several recent experiments have revealed new interesting physical properties in a monoand a few-layer TMDs such as series of phase transitions and novel superconductivity, being different from those shown in their bulk forms [19][20][21][22][23][24][25][26][27][28][29][30][31] . Formation of charge density waves (CDWs) in three-dimensional metallic TMDs has attracted interests for the last couple of decades and origins of CDWs in some materials are still not settled yet 32,33 .…”

Section: Introductionmentioning

confidence: 99%

Quasiparticle energy bands and Fermi surfaces of monolayer NbSe2

Kim

Son

2017

Phys. Rev. B

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A quasiparticle band structure of a single layer 2H-NbSe2 is reported by using first-principles GW calculation. We show that a self-energy correction increases the width of a partially occupied band and alters its Fermi surface shape when comparing those using conventional mean-field calculation methods. Owing to a broken inversion symmetry in the trigonal prismatic single layer structure, the spin-orbit interaction is included and its impact on the Fermi surface and quasiparticle energy bands are discussed. We also calculate the doping dependent static susceptibilities from the band structures obtained by the mean-field calculation as well as GW calculation with and without spinorbit interactions. A complete tight-binding model is constructed within the three-band third nearest neighbour hoppings and is shown to reproduce our GW quasiparticle energy bands and Fermi surface very well. Considering variations of the Fermi surface shapes depending on self-energy corrections and spin-orbit interactions, we discuss the formations of charge density wave (CDW) with different dielectric environments and their implications on recent controversial experimental results on CDW transition temperatures.

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Charge density wave transition in single-layer titanium diselenide

Cited by 241 publications

References 28 publications

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂

Critical Role of the Exchange Interaction for the Electronic Structure and Charge-Density-Wave Formation in TiSe2

Quasiparticle energy bands and Fermi surfaces of monolayer NbSe2

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Charge density wave transition in single-layer titanium diselenide

Cited by 241 publications

References 28 publications

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS 2

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS 2

Critical Role of the Exchange Interaction for the Electronic Structure and Charge-Density-Wave Formation in TiSe2

Quasiparticle energy bands and Fermi surfaces of monolayer NbSe2

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Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂

Dimensionality-driven phonon softening and incipient charge density wave instability in TiS ₂