Infrared study of the electronic instabilities in tantalum disulfide and tantalum diselenide

Strong enhancement of superconductivity at high pressures within the charge-density-wave states of2H−TaS2and2H−TaSe2Freitas1, Rodière2, Osorio3 et al. 2016Phys. Rev. B1128521View full textAdd to dashboardCite

“…This order-disorder transition is characterized by the absence of unstable zero energy phonon softening at the transition, as is confirmed by the reported nonzero soft mode for 2H -TaSe 2 [55]. Furthermore, the idea of preexisting disordered deformations stems from the observation of a gap that is five times larger than expected from the weak-coupling formula [56] and could be used to explain the robustness of the CDW at higher pressures. It would imply, though, that the model describes better the transition metal dichalcogenides with large interlayer separations, 2H -TaSe 2 and 2H -TaS 2 , than 2H -NbSe 2 .…”

Strong electron-lattice coupling as the mechanism behind charge density wave transformations in transition-metal dichalcogenides

“…Superconductivity in 2H-TaSe 2 , 2H-TaS 2 and 2H-NbSe 2 takes place on the background of the CDW phase. The CDW gap values ∼ 0.1 eV surprisingly large in comparison with the values of transition temperatures, T CDW (Ta) = 122 K and T CDW (Nb) = 33.5 K, were observed via the dI/dV characteristics in the tunneling experiments [3]. The gap of such order of magnitude is noticeable in the infrared data [4] (2H-TaSe 2 ) even close to the transition temperature.…”

“…2 both contradict to the experimental data [3,4] and to their analysis and the interpretation [5,8]. In spite of that, the two concepts are commonly used for interpretation of results even in recent ARPES experiments (see, e.g., [9,10]).…”

Band structure of transition metal compounds

“…The results for TaS2 have also been compared with reflectivity spectra obtained by Barker et al [66].…”