Pressure-driven semiconducting-semimetallic transition in SnSe

Abstract

In this work, we report the pressure-dependent electrical transport and structural properties of SnSe. In our experiments an electronic transition from a semiconducting to semimetallic state was observed at 12.6 GPa, followed by an orthorhombic to monoclinic structural transition. Hall effect measurements indicate that both the carrier concentration and mobility vary abnormally accompanied by the semimetallic electronic transition. First-principles band structure calculations confirm the semiconducting-semimetallic transition, and reveal that the semimetallic character of SnSe can be attributed to the enhanced coupling of Sn-5s, Sn-5p, and Se-3p orbitals under compression that results in the broadening of energy bands and subsequently the closure of the band gap. The pressure modulated variations of electrical transport and structural properties may provide an approach to improving the thermoelectric properties of SnSe.

High-performance SnSe thermoelectric materials: Progress and future challenge

“…Besides, the study of shear stress as a function of strain under different shear directions is also important for the applications of SnSe thermoelectric materials. indicating the transition region from semiconductor to metallic or semi-metallic region under a pressure [143]. The crystal structure is distorted with increasing the pressure.…”

Topological Dirac line nodes and superconductivity coexist in SnSe at high pressure

“…To investigate its experimental manifestations in electronic properties, we carried out electrical transport measurements on single crystal SnSe up to 55.0 GPa. Figure 4(a-d) shows the temperature dependence of the dc electrical resistance of SnSe in the temperature range of 1.8-300 K. At 0.4 GPa, a semiconducting behavior (dR/dT < 0) is observed in the whole temperature range as that of semiconducting SnSe at ambient pressure [24,46]. With increasing pressure, the whole resistance decreases rapidly implying a remarkable reduction in energy gap of the material with pressure (see Fig.…”

“…Under ambient conditions, SnSe is an ordinary semiconductor and has a layered orthorhombic (Pnma, No. 62) GeS-type crystal structure [24]. Interestingly, SnSe with cubic NaCl-type structure was theoretically proposed to be a native topological crystalline insulator [25] with surface states protected by mirror symmetry [25][26][27][28][29].…”

High‐Performance Thermoelectric SnSe: Aqueous Synthesis, Innovations, and Challenges

“…In this regard, SnSe has the high anharmonic degree, which can be used to further reduce κ l . For example, inducing point defects (either vacancies or heteroatoms) into the matrix can strengthen the anharmonic bonding, and can apply for appropriate pressure to alter the anharmonicity 214,234–236. Other calculation work indicated that the coupled instability of electronic orbitals and lattice dynamics is the origin of the strong anharmonicity in SnSe, which causes the ultralow κ l 237…”

“…All these 2D nanosized crystal defects can strengthen the phonon scattering at induced strain fields, contributing to reducing κ l . It should be noticed that reducing the grain size (grain refinement) may also weaken the anisotropy of SnSe; however, applying high pressure during sintering process has been demonstrated as an effective way to improve the anisotropy,61,235 thus the grain refinement is still a good strategy to achieve high thermoelectric performance in polycrystalline SnSe along both directions.…”