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Puzzling results explained: A multiband approach to Coulomb drag and indirect excitons

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Eric Whitefield
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Taking a multiband approach explains 'electron-hole reverse drag' and exciton formation

Mystifying experimental results obtained independently by two research groups in the USA seemed to show coupled holes and electrons moving in the opposite direction to theory.

Now, a new theoretical study has explained the previously mysterious result, by showing that this apparently contradictory phenomenon is associated with the bandgap in dual-layer graphene structures, a bandgap which is very much smaller than in conventional semiconductors.

Exciton transport offers great promise to researchers, including the potential for ultra-low dissipation future electronics.

An exciton is a composite particle: an electron and a 'hole' (a positively charged 'quasiparticle' caused by the absence of an electron) bound together by their opposite electrical charges.

If electrons in the top ('drive') sheet are accelerated by an applied voltage, then each partnering hole in the lower ('drag') sheet can be 'dragged' by its electron.

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Eric Whitefield
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