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Phys Rev Lett. 2017 Mar 31;118(13):137002. doi: 10.1103/PhysRevLett.118.137002. Epub 2017 Mar 28.

Pressure-Stabilized Tin Selenide Phase with an Unexpected Stoichiometry and a Predicted Superconducting State at Low Temperatures.

Author information

1
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
2
Center for High Pressure Science and Technology Advanced Research, 10 Dongbeiwang West Road, Haidian, Beijing 100094, China.

Abstract

Tin-selenium binary compounds are important semiconductors that have attracted much interest for thermoelectric and photovoltaic applications. As tin has a +2 or +4 oxidation state and selenium has an oxidation number of -2, only SnSe and SnSe_{2} have been observed. In this work, we show that the chemical bonding between tin and selenium becomes counterintuitive under pressures. Combining evolutionary algorithms and density functional theory, a novel cubic tin-selenium compound with an unexpected stoichiometry 3∶4 has been predicted and further synthesized in laser-heated diamond anvil cell experiments. Different from the conventional SnSe and SnSe_{2} semiconductors, Sn_{3}Se_{4} is predicted to be metallic and exhibit a superconducting transition at low temperatures. Based on electron density and Bader charge analysis, we show that Sn_{3}Se_{4} has a mixed nature of chemical bonds. The successful synthesis of Sn_{3}Se_{4} paves the way for the discovery of other IV-VI compounds with nonconventional stoichiometries and novel properties.

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