Predication of topological states in the allotropes of group-IV elements |
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| Authors: | Chengyong Zhong |
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| Affiliation: | 1. National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China2. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China3. Institute for Advanced Study, Chengdu University, Chengdu 610106, China |
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| Abstract: | Three-dimensional (3D) topological insulators (TIs) have been studied for approximately fifteen years, but those made from group-IV elements, especially Ge and Sn, seem particularly attractive owing to their nontoxicity, sizable intrinsic spin–orbit coupling (SOC) strength and natural compatibility with the current semiconductor industry. However, group-IV elemental TIs have rarely been reported, except for the low temperature phase of α-Sn under strain. Here, based on first-principles calculations, we propose new allotropes of Ge and Sn, named T5-Ge/Sn, as desirable TIs. These new allotropes are also highly anisotropic Dirac semimetals if the SOC is turned off. To the best of our knowledge, T5-Ge/Sn are the first 3D allotropes of Ge/Sn that possess topological states in their equilibrium states at room temperature. Additionally, their isostructures of C and Si are metastable indirect and direct semiconductors. Our work not only reveals two promising TIs, but more profoundly, we justify the advantages of group-IV elements as topological quantum materials (TQMs) for fundamental research and potential practical applications, and thus reveal a new direction in the search for desirable TQMs. |
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| Keywords: | topological insulators topological semimetals group-IV elements first-principles calculations |
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