Interplay between electron-electron interaction and electron-phonon coupling near the Fermi surface of1T−TaS2

Abstract

We present a detailed high-resolution angle-resolved photoemission study of the electronic band structure of the room-temperature quasicommensurate charge-density-wave phase of 1T-TaS 2 . In particular, we show that no crossings of the Fermi level are visible in the complete Brillouin zone, indicating that an electron-electron correlation-induced pseudogap in the Ta 5d derived band exists already above the Mott localization-induced transition at 180 K. Moreover, we find that the electronic structure is governed by at least two quasiparticle peaks, which can be assigned to electrons from starlike shells of Ta atoms within the distorted crystal lattice. These peaks show quasilocalized ͑dispersionless͒ behavior in parts of the Brillouin zone where the one-particle band is unoccupied and they follow the one-particle dispersion in the occupied part. In order to address the question of possible Fermi-surface ͑FS͒ nesting, we scanned the remaining remnant FS and found regions with a considerable decrease of spectral weight. However, we find no clear evidence for FS nesting.

Pressure Induced Superconductivity in Pristine1T−TiSe2

“…On the contrary, the pressure does not change total concentration of electrons per unit cell in TiSe 2 layers, but rather enhances the two-band character of the system by increasing the number of electrons and holes in Ti-and Se-derived bands, respectively [22,23]. The positive R H reflects the fact that the effective mass of holes in the valence band is approximately 1=20 of the effective mass of electrons in the conduction band [24][25][26]. This large asymmetry is evidently compensated in Cu-intercalated materials, even for Cu concentrations much lower than those required for the superconductivity to set in [5].…”

The Peierls transition in low-dimensional electronic crystals

“…These experiments have been used to study the mechanism of CDW formation. Both Fermi surface nesting (Straub et al, 1999) and alternative mechanisms have been proposed (Rice & Scott, 1975;Pillo et al, 2000;Liu et al, 2000).…”

Atomistic origin of an ordered superstructure induced superconductivity in layered chalcogenides

“…Layered transition-metal dichalcogenides (TMDs) 5,6 serve as an ideal platform for probing the intricate interplay in that their intrinsic two-dimensional structure is susceptible to electronic instability. This effect is especially pronounced in 1T-TaS 2 , where its CDW phases are diverse (that is, nearly commensurate CDW (NCCDW) and commensurate CDW (CCDW) phases) and its CCDW phase is compatible to the Mott insulating phase due to the strong electron-phonon and electron-electron interactions [7][8][9][10][11][12] .…”