Millimetre-long transport of photogenerated carriers in topological insulators.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31844140.
- Also identified by DOI 10.1038/s41467-019-13711-3 and PMC identifier 6915787.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Excitons are spin integer particles that are predicted to condense into a coherent quantum state at sufficiently low temperature. Here by using photocurrent imaging we report experimental evidence of formation and efficient transport of non-equilibrium excitons in Bi<sub>2-x</sub>Sb<sub>x</sub>Se<sub>3</sub> nanoribbons. The photocurrent distributions are independent of electric field, indicating that photoexcited electrons and holes form excitons. Remarkably, these excitons can transport over hundreds of micrometers along the topological insulator (TI) nanoribbons before recombination at up to 40 K. The macroscopic transport distance, combined with short carrier lifetime obtained from transient photocurrent measurements, indicates an exciton diffusion coefficient at least 36 m<sup>2</sup> s<sup>-1</sup>, which corresponds to a mobility of 6 × 10<sup>4</sup> m<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup> at 7 K and is four order of magnitude higher than the value reported for free carriers in TIs. The observation of highly dissipationless exciton transport implies the formation of superfluid-like exciton condensate at the surface of TIs.