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Dirac cones in two-dimensional borane?

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If you have a question about this talk, please contact Dr. Mike Towler.

Interest in two-dimensional materials has skyrocketed in the last few years, both from an experimental and theoretical point of view. From Dirac cones in graphene and novel phenomena in multilayer graphene, to spintronics in MoS2 monolayers, this is an area of very active research. A lot of effort is also spent in finding novel materials with promising properties.

In this work I will be talking about a theoretically predicted compound: two-dimensional borane, a single-layered material of BH stoichiometry, with promising electronic properties. The basis of the structure is a puckered and distorted trigonal boron network. Bonding with Hydrogen atoms happens outside the boron layer. We argue this material may be synthesised by exfoliating a weakly bonded high-pressure polymorph.

DFT calculations support the existence of Dirac cones meeting at the Fermi energy Ef. The curvature of the cones is lower than in graphene, and so closer to the ideal linear dispersion. The velocity according to DFT bands is also higher than in graphene. Both symmetry and, in this case, electron counting arguments play a key role in the resilience of these cones. Chemical bonding analysis reveals the boron atoms in the network are bound by delocalized four-center two-electron bonds.

This talk is part of the Electronic Structure Discussion Group series.

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