Spectroscopic trace of the Lifshitz transition and multivalley activation in thermoelectric SnSe under high pressure

Abstract

Multivalley systems offer not only exciting physical phenomena but also the possibility of broad utilization. Identifying an important platform and understanding its physics are paramount tasks to improve their capability for application. Here, we investigate a promising candidate, the semiconductor SnSe, by optical spectroscopy and density functional theory calculations. Upon applying pressure to lightly doped SnSe, we directly monitored the phase transition from semiconductor to semimetal. In addition, heavily doped SnSe exhibited a successive Lifshitz transition, activating multivalley physics. Our comprehensive study provides insight into the effects of pressure and doping on this system, leading to promising routes to tune the material properties for advanced device applications, including thermoelectrics and valleytronics.

Structural, Vibrational, and Electronic Properties of 1D-TlInTe2 under High Pressure: A Combined Experimental and Theoretical Study

“…Therefore, the combination of L1- and L2-type transitions might be responsible for the emergence of superconductivity in the B37 phase of TlInTe 2 as observed in our transport measurements at 5.7 GPa. Analogous to TlInTe 2 , pressure-induced Fermi surface topology change (Lifshitz transition) is reported for quasi-2D ZrSiTe, ThFeAsN, SnSe, , and bulk H 3 S …”

“…Therefore, the combination of L1-and L2-type transitions might be responsible for the emergence of superconductivity in the B37 phase of TlInTe 2 as observed in our transport measurements at 5.7 GPa. Analogous to TlInTe 2 , pressure-induced Fermi surface topology change (Lifshitz transition) is reported for quasi-2D ZrSiTe, 28 ThFeAsN, 27 SnSe, 29,30 and bulk H 3 S. 31 To discern the frequency reversal of the A g phonon mode around 12 GPa, we carried out a detailed line shape analysis of phonon modes. Surprisingly, an obvious asymmetry begins to emerge at P = 8.8 GPa and above to the left (low frequency region) of the A g mode.…”

“…Strikingly, the monolayer of TlSe (S.G: I 4/ mcm ) is predicted to be a topological insulator under uniaxial compression while InTe shows a band inversion under hydrostatic pressure . The electronic structure and Fermi surface topology changes under high pressure can provide insights into band inversion and/or electronic topological transitions (including Lifshitz transition). − Preliminary high-pressure Raman studies on TlInTe 2 up to ∼17 GPa suggest phase transition at 7 GPa and signatures of another phase transition at higher pressure . The existence of a high-pressure phase at 7 GPa is still unexplored due to the lack of high-pressure X-ray diffraction (XRD) studies.…”

Giant Room‐Temperature Power Factor inp‐Type Thermoelectric SnSe under High Pressure

“…[ 45 ] Thus, the hump in our thermopower curves at 1–2 GPa (Figure 3a,b) can be attributed to this Lifshitz transition. [ 45,46 ] Note that the enhanced power factor of heavily p ‐doped SnSe crystals attained at ambient conditions, [ 18,34,36,38 ] was also attributed in the literature to a multi‐valley conductivity. In the last case, the heavy p ‐doping shifts the top of the valence band of SnSe, and for hole concentrations exceeding ≈4–5 × 10 19 см −3 the second valence band should cross the Fermi level and contribute to electrical conductivity.…”

Stabilizing superconductivity of ternary metal pentahydride $$\hbox {CaCH}_{{5}}$$ via electronic topological transitions under high pressure from first principles evolutionary algorithm

“…As a result of this, the Pm structure exhibited the electronic topological transition (ETT), which referred to as the Lifshitz transition 38 . This because the Lifshitz transition is a kind of ETT, it should be mentioned that the ETT is change of the band shape under high pressure 39 , 40 . It is well-known that the Lifshitz transition is associated with an ETT because the ETT originates from the electronic band structure.…”