Fermi surface of layered compounds and bulk charge density wave systems

Clerc, F.; Battaglia, Corsin; Cercellier, H.; Monney, Claude; Berger, H.; Despont, Laurent; Garnier, M. G.; Aebi, Philipp

doi:10.1088/0953-8984/19/35/355002

Cited by 46 publications

(40 citation statements)

References 71 publications

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“…More important than the change in photoemission intensity [21,22] is the modification of the graphene band structure by the potential exerted by the cluster superlattice. The most prominent effect is the renormalization of the group velocity expressed in highly anisotropic Dirac cones.…”

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confidence: 99%

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice

et al. 2010

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We present a new method to engineer the charge carrier mobility and its directional asymmetry in epitaxial graphene by using metal cluster superlattices self-assembled onto the moiré pattern formed by graphene on Ir(111). Angle-resolved photoemission spectroscopy reveals threefold symmetry in the band structure associated with strong renormalization of the electron group velocity close to the Dirac point giving rise to highly anisotropic Dirac cones. We further find that the cluster superlattice also affects the spectral-weight distribution of the carbon bands as well as the electronic gaps between graphene states. DOI: 10.1103/PhysRevLett.105.246803 PACS numbers: 73.20.Àr, 73.21.Cd, 73.22.Pr, 79.60.Ài Graphitic materials have attracted strong scientific interest because they exhibit exotic phenomena such as superconductivity or the anomalous quantum Hall effect [1]. Graphene (gr) is the building block of these materials; it is wrapped up into fullerenes, rolled up into carbon nanotubes, or stacked into 3D graphite. It presents a model system to investigate the influence of many-body interactions on the electron dynamics in these materials. In addition, the exceptional electronic mobility makes graphene a candidate material for next generation electronic devices [2]. Freestanding graphene is a zero-gap semiconductor. Because most electronic applications require a gap between valence and conduction bands, considerable effort has been spent to induce and control the opening of such a band gap [3][4][5][6].A related, and for applications equally relevant, issue is the ability to tailor the band dispersion. The speed with which information can be transmitted along a graphene layer depends on the charge carrier group velocity. Close to the K points, the bands of freestanding graphene have a linear dispersion well described by the relativistic Dirac equation for massless neutrinos. The resulting Dirac cones are trigonally warped due to the chiral nature of graphene charge carriers in the equivalent A and B carbon sublattices [7]. The ability to increase and tailor this anisotropy would open a manifold of new applications. Several theoretical studies suggest that this goal can be reached by applying an external periodic potential with nanometer period giving rise to highly anisotropic Dirac cones [8][9][10][11].Epitaxial graphene layers grown on lattice mismatched close-packed metal substrates, such as Pt (111) Here we demonstrate with angle-resolved photoemission spectroscopy (ARPES) that an Ir cluster superlattice grown on the gr=Irð111Þ-(9:32 AE 0:15 Â 9:32 AE 0:15) moiré structure [13,15] gives rise to significant group velocity and Dirac cone asymmetries. We attribute this to a much stronger periodic potential caused by the cluster superlattice than by the moiré itself. H decorated gr=Irð111Þ has been reported to give rise to band gap opening but not to the Dirac cone asymmetries reported here [6]. We thereby confirm theoretical predictions and present a new way to tailor the directionality of carrier mobilit...

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Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice

et al. 2010

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“…Experimentally, TiSe 2 samples consistently exhibit a characteristic and marked upturn in longitudinal resistivity that accompanies the CDW transition in TiSe 2 . This transport signature has been experimentally observed since the early experiments 3 and the sudden increase registered in ρ(T ) around T c is frequently used to track T c as a function of other experimental parameters 2,4 . According to the excitonic mechanism, in addition to contributions from scattering by CDW fluctuations in the vicinity of T c , that signature might be also directly related to the suppression of electronic states as the transition takes place.…”

Section: S-ie Mapping Chemical Potential To Doping Introduced By Cumentioning

confidence: 82%

Reproduction of the Charge Density Wave Phase Diagram in1T−TiSe2Exposes its Excitonic Character

et al. 2018

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Recent experiments suggest that excitonic degrees of freedom play an important role in precipitating the charge density wave (CDW) transition in 1T-TiSe2. Through systematic calculations of the electronic and phonon spectrum based on density functional perturbation theory, we show that the predicted critical doping of the CDW phase overshoots the experimental value by one order of magnitude. In contrast, an independent self-consistent many-body calculation of the excitonic order parameter and renormalized band structure is able to capture the experimental phase diagram in extremely good qualitative and quantitative agreement. This demonstrates that electron-electron interactions and the excitonic instability arising from direct electron-hole coupling are pivotal to accurately describe the nature of the CDW in this system. This has important implications to understand the emergence of superconductivity within the CDW phase of this and related systems.

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“…[1][2][3] Due to their layered structure, they can be easily intercalated by foreign atoms in their so-called van der Waals gap, providing a chemical parameter for tuning new phenomena. In this way, for instance, superconductivity can be enhanced or suppressed, sometimes in competition with CDW phases.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent photoemission on1T-TiSe2: Interpretation within the exciton condensate phase model

et al. 2010

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The charge-density-wave phase transition of 1T-TiSe 2 is studied by angle-resolved photoemission over a wide temperature range. An important chemical-potential shift which strongly evolves with temperature is evidenced. In the framework of the exciton condensate phase, the detailed temperature dependence of the associated order parameter is extracted. Having a mean-field-like behavior at low temperature, it exhibits a nonzero value above the transition, interpreted as the signature of strong excitonic fluctuations, reminiscent of the pseudogap phase of high-temperature superconductors. Integrated intensity around the Fermi level is found to display a trend similar to the measured resistivity and is discussed within the model.

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Fermi surface of layered compounds and bulk charge density wave systems

Cited by 46 publications

References 71 publications

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice

Reproduction of the Charge Density Wave Phase Diagram in1T−TiSe2Exposes its Excitonic Character

Temperature-dependent photoemission on1T-TiSe2: Interpretation within the exciton condensate phase model

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