Journal
NANO LETTERS
Volume 14, Issue 8, Pages 4767-4771Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl501907g
Keywords
Quantum spin Hall insulator; topological edge states; dissipationless transport; bismuth monobromide; two-dimensional materials; first-principles calculations
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Funding
- MOST Project of China [2014CB920903, 2013CB921903, 2011CBA00100]
- NSF of China [11174337, 11225418, 11374033]
- SRFDPHE of China [20121101110046, 20131101120052]
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Quantum spin Hall (QSH) insulators have gapless topological edge states inside the bulk band gap, which can serve as dissipationless spin current channels. The major challenge currently is to find suitable materials for this topological state. Here, we predict a new large-gap QSH insulator with bulk direct band gap of similar to 0.18 eV, in single-layer Bi4Br4, which could be exfoliated from its three-dimensional bulk material due to the weakly bonded layered structure. The band gap of single-layer Bi4Br4 is tunable via strain engineering, and the QSH phase is robust against external strain. Moreover, because this material consists of special one-dimensional molecular chain as its basic building block, the single layer Bi4Br4 could be torn to ribbons with clean and atomically sharp edges. These nanoribbons, which have single-Dirac-cone edge states crossing the bulk band gap, are ideal wires for dissipationless transport. Our work thus provides a new promising material for experimental studies and practical applications of the QSH effect.
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