Electronic, vibrational, and electron–phonon coupling properties in SnSe2 and SnS2 under pressure. Issue 46 (2nd November 2020)

• Record Type: Journal Article
• Authors: Kafle, Gyanu Prasad; Heil, Christoph; Paudyal, Hari; Margine, Elena R.
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 46(2020)
• Page Start: 16404
• Page End: 16417
• Publication Date: 2020-11-02
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc04356g
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : First-principles calculations are used to investigate the effect of pressure on lattice stability, electron–phonon properties, and superconductivity in SnSe2 and SnS2 . Abstract : The tin-selenide and tin-sulfide classes of materials undergo multiple structural transitions under high pressure leading to periodic lattice distortions, superconductivity, and topologically non-trivial phases, yet a number of controversies exist regarding the structural transformations in these systems. We perform first-principles calculations within the framework of density functional theory and a careful comparison of our results with available experiments on SnSe2 reveals that the apparent contradictions among high-pressure results can be attributed to differences in experimental conditions. We further demonstrate that under hydrostatic pressure a superstructure can be stabilized above 20 GPa in SnS2 via a periodic lattice distortion as found recently in the case of SnSe2, and that this pressure-induced phase transition is due to the combined effect of Fermi surface nesting and electron–phonon coupling at a momentum wave vector q = (1/3, 1/3, 0). In addition, we investigate the contribution of nonadiabatic corrections on the calculated phonon frequencies, and show that the quantitative agreement between theory and experiment for the high-energy A1g phonon mode is improved when these effects are taken into account. Finally, we examine the nature of the superconducting state recently observed in SnSe2 under nonhydrostatic pressure and predict the emergence of superconductivity with a comparable critical temperature in SnS2 under similar experimental conditions. Interestingly, in the periodic lattice distorted phases, the critical temperature is found to be reduced by an order of magnitude due to the restructuring of the Fermi surface.