Efthimiopoulos Ilias, Berg Matthias, Bande Annika, Puskar Ljiljana, Ritter Eglof, Xu Wei, Marcelli Augusto, Ortolani Michele, Harms Martin, Müller Jan, Speziale Sergio, Koch-Müller Monika, Liu Yong, Zhao Li-Dong, Schade Ulrich
GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany.
Phys Chem Chem Phys. 2019 Apr 24;21(17):8663-8678. doi: 10.1039/c9cp00897g.
We have conducted a comprehensive investigation of the optical and vibrational properties of the binary semiconductor SnSe as a function of temperature and pressure by means of experimental and ab initio probes. Our high-temperature investigations at ambient pressure have successfully reproduced the progressive enhancement of the free carrier concentration upon approaching the Pnma → Bbmm transition, whereas the pressure-induced Pnma → Bbmm transformation at ambient temperature, accompanied by an electronic semiconductor → semi-metal transition, has been identified for bulk SnSe close to 10 GPa. Modeling of the Raman-active vibrations revealed that three-phonon anharmonic processes dominate the temperature-induced mode frequency evolution. In addition, SnSe was found to exhibit a pressure-induced enhancement of the Born effective charge. Such behavior is quite unique and cannot be rationalized within the proposed effective charge trends of binary materials under pressure.
我们通过实验和从头算方法，对二元半导体SnSe的光学和振动性质随温度和压力的变化进行了全面研究。我们在常压下的高温研究成功再现了接近Pnma→Bbmm转变时自由载流子浓度的逐渐增加，而在室温下压力诱导的Pnma→Bbmm转变，伴随着电子半导体→半金属转变，已在接近10 GPa的块状SnSe中得到确认。对拉曼活性振动的建模表明，三声子非谐过程主导了温度诱导的模式频率演化。此外，发现SnSe表现出压力诱导的玻恩有效电荷增强。这种行为非常独特，在所提出的二元材料在压力下的有效电荷趋势范围内无法得到合理解释。
