Pressure-dependent semiconductor to semimetal and Lifshitz transitions in 2H-MoTe₂: Raman and first-principles studies

Abstract

High pressure Raman spectroscopy of bulk 2H-MoTe 2 upto ∼ 29 GPa is shown to reveal two phase transitions (at ∼ 6 and 16.5 GPa), which are analyzed using first-principles density functional theoretical calculations. The transition at 6 GPa is marked by changes in the pressure coefficients of A 1g and E 1 2g Raman mode frequencies as well as in their relative intensity. Our calculations show that this is an isostructural semiconductor to a semimetal transition. The transition at ∼ 16.5 GPa is identified with the changes in linewidths of the Raman modes as well as in the pressure coefficients of their frequencies. Our theoretical analysis clearly shows that the structure remains the same upto 30 GPa. However, the topology of the Fermi-surface evolves as a function of pressure, and abrupt appearance of electron and hole pockets at P ∼ 20 GPa marks a Lifshitz transition. a electronic mail:asood@physics.iisc.ernet.in

Hidden spin-polarized bands in semiconducting 2H-MoTe2

“…The valence band maximum (VBM) is located at the K high-symmetry point of the BZ and the conduction band minimum (CBM) at an arbitrary point between K and (labeled Q) [16]. Previous DFT calculations reported pressure coefficient of the indirect band gap around −7.3 meV/kbar, corresponding to a transition between k-points away from K or [28]. Our calculations provide a different picture of the electronic dispersion, in consistency with angle-resolved photoemission spectroscopy (ARPES) measurements [29], and predict an indirect band gap pressure coefficient around −4.76 meV/kbar.…”

Pressure-induced Lifshitz transition in NbP: Raman, x-ray diffraction, electrical transport, and density functional theory

“…11(a)]. As the hydrostatic pressure does not alter the symmetry of the crystal, the energy levels do not split, but those near the Fermi energy change notably giving rise to pressure-induced transfer of electrons from one pocket to another in order to maintain the total number of carriers (i.e., the size of the electron and hole pockets changes with pressure) [37]. Interestingly, at 12 GPa a small hole pocket appears along the -N path [see Fig.…”

Strain and Electric Field Controllable Schottky Barriers and Contact Types in Graphene-MoTe2 van der Waals Heterostructure

“…A vacuum space of 25 Å along the z direction is adopted to avoid the interaction between the neighboring layers. As it was revealed that the spin-orbit coupling effect on band structures of 2H-MoTe 2 is very weak [51], all of the calculations do not consider the spin-orbit coupling.…”