Ultrafast manipulation of topologically enhanced surface transport driven by mid-infrared and terahertz pulses in Bi<sub>2</sub>Se<sub>3</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30723197.
- Also identified by DOI 10.1038/s41467-019-08559-6 and PMC identifier 6363774.
- 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
Topology-protected surface transport of ultimate thinness in three-dimensional topological insulators (TIs) is breaking new ground in quantum science and technology. Yet a challenge remains on how to disentangle and selectively control surface helical spin transport from the bulk contribution. Here we use the mid-infrared and terahertz (THz) photoexcitation of exclusive intraband transitions to enable ultrafast manipulation of surface THz conductivity in Bi<sub>2</sub>Se<sub>3</sub>. The unique, transient electronic state is characterized by frequency-dependent carrier relaxations that directly distinguish the faster surface channel than the bulk with no complication from interband excitations or need for reduced bulk doping. We determine the topological enhancement ratio between bulk and surface scattering rates, i.e., γ<sub>BS</sub>/γ<sub>SS</sub> ~3.80 in equilibrium. The ultra-broadband, wavelength-selective pumping may be applied to emerging topological semimetals for separation and control of the protected transport connected with the Weyl nodes from other bulk bands.