Donarini A, Niklas M, Schafberger M, Paradiso N, Strunk C, Grifoni M. Coherent population trapping by dark state formation in a carbon nanotube quantum dot.
Nat Commun 2019;
10:381. [PMID:
30670686 PMCID:
PMC6343009 DOI:
10.1038/s41467-018-08112-x]
[Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 11/28/2018] [Indexed: 11/10/2022] Open
Abstract
Illumination of atoms by resonant lasers can pump electrons into a coherent superposition of hyperfine levels which can no longer absorb the light. Such superposition is known as a dark state, because fluorescent light emission is then suppressed. Here we report an all-electric analogue of this destructive interference effect in a carbon nanotube quantum dot. The dark states are a coherent superposition of valley (angular momentum) states which are decoupled from either the drain or the source leads. Their emergence is visible in asymmetric current−voltage characteristics, with missing current steps and current suppression which depend on the polarity of the applied source-drain bias. Our results demonstrate coherent-population trapping by all-electric means in an artificial atom.
Transport in quantum systems is complex and can be suppressed by coherent superposition of the involved states. Here, the authors find all-electronic suppression of transport in a carbon nanotube originating from coherent population trapping and give criteria for the presence of such a dark state.
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