TY - JOUR
T1 - A Non-Natural Wurtzite Polymorph of HgSe
T2 - A Potential 3D Topological Insulator
AU - Dumett Torres, Daniel
AU - Banerjee, Progna
AU - Pamidighantam, Sudhakar
AU - Jain, Prashant K.
N1 - Funding Information:
This material is based upon work supported by the National Science Foundation under Grant NSF CHE-1455011 (support for D.D.T.). We acknowledge the donors of the American Chemical Society Petroleum Research Fund for support of this research (support of P.B.). We thank the Blue Waters supercomputing facility, the National Center for Supercomputing Applications (NCSA), the Extreme Science and Engineering Discovery Environment (XSEDE), and the Science and Engineering Applications Grid for computational resources.
Publisher Copyright:
© 2017 American Chemical Society.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2017/8/8
Y1 - 2017/8/8
N2 - This article demonstrates the power of topotactic synthesis coupled with density functional theory (DFT) for accessing and exploring new phases of matter. Naturally occurring HgSe is a semimetal with a zero gap. Unlike this natural zincblende form of HgSe, our DFT investigations predict that wurtzite HgSe has both an inverted band structure and a band gap, making it a 3D topological insulator (TI). Calculated band structures of HgxCd1-xSe alloys containing strongly relativistic Hg and weakly relativistic Cd show that band gap opening is a consequence of symmetry breaking resulting from a combination of crystal anisotropy and the scalar relativistic effect of Hg electrons. The relativistic contribution of Hg is significant enough in alloys with x ≥ 0.33 for achieving 3D TI behavior at room temperature. We experimentally realize the non-natural wurtzite form by topotactic ion exchange of wurtzite CdSe nanocrystals (NCs), which yields alloy NCs in the range x = 0-0.54 whose measured band gaps follow the predicted trend. We introduce crystal anisotropy as a new handle for expanding the classes of TI materials and also shed light on electronic principles in nanocrystalline alloys containing relativistic metals. NCs of this new wurtzite phase can become platforms for discovery of rich topological states and properties.
AB - This article demonstrates the power of topotactic synthesis coupled with density functional theory (DFT) for accessing and exploring new phases of matter. Naturally occurring HgSe is a semimetal with a zero gap. Unlike this natural zincblende form of HgSe, our DFT investigations predict that wurtzite HgSe has both an inverted band structure and a band gap, making it a 3D topological insulator (TI). Calculated band structures of HgxCd1-xSe alloys containing strongly relativistic Hg and weakly relativistic Cd show that band gap opening is a consequence of symmetry breaking resulting from a combination of crystal anisotropy and the scalar relativistic effect of Hg electrons. The relativistic contribution of Hg is significant enough in alloys with x ≥ 0.33 for achieving 3D TI behavior at room temperature. We experimentally realize the non-natural wurtzite form by topotactic ion exchange of wurtzite CdSe nanocrystals (NCs), which yields alloy NCs in the range x = 0-0.54 whose measured band gaps follow the predicted trend. We introduce crystal anisotropy as a new handle for expanding the classes of TI materials and also shed light on electronic principles in nanocrystalline alloys containing relativistic metals. NCs of this new wurtzite phase can become platforms for discovery of rich topological states and properties.
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U2 - 10.1021/acs.chemmater.7b01674
DO - 10.1021/acs.chemmater.7b01674
M3 - Article
AN - SCOPUS:85027310772
SN - 0897-4756
VL - 29
SP - 6356
EP - 6366
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 15
ER -