Abstract
Fano resonance is a fundamental physical process that strongly affects the electronic transport, optical, and vibronic properties of matter. Here, we provide the first experimental demonstration of its profound effect on spin properties in semiconductor nanostructures. We show that electron spin generation in InAs/GaAs quantum-dot structures is completely quenched upon spin injection from adjacent InGaAs wetting layers at the Fano resonance due to coupling of light-hole excitons and the heavy-hole continuum of the interband optical transitions, mediated by an anisotropic exchange interaction. Using a master equation approach, we show that such quenching of spin generation is robust and independent of Fano parameters. This work therefore identifies spin-dependent Fano resonance as a universal spin loss channel in quantum-dot systems with an inherent symmetry-breaking effect.
Highlights
Fano resonance (FR) emerges as a result of quantum interference between two spectrally overlapping pathways —one channel through a discrete level and the other via continuum states [1]
Using InAs/GaAs quantumdot (QD) structures (QDS) as a sensitive spin detector, we show that optical generation of electron spin polarization in a nearby ultrathin quantum well is completely quenched when circularly polarized excitation is tuned in resonance with FR formed between a light-hole exciton (XL) and a continuum of the band-to-band (BB) transition between the electron and heavy-hole (HH) subband (e-HH)
The observed quenching of optical spin generation is accompanied by the presence of a giant anisotropic exchange interaction (AEI) of the XL, which suggests an effect of localization and symmetry breaking due to the dot-well interaction
Summary
1.081 1.170 1.241 1.190 under the Stranski-Krastanov mode, with a 1.8-monolayer thin, coherently strained InAs quantum well, i.e., a wetting layer (WL), being formed right beneath the QDS layer. A detailed description of the growth parameters can be found elsewhere [19]. The dot-well structure facilitates a sensitive detection of electron spins generated in the WL by monitoring spin polarization of the electrons injected to the nearby QDS. Optical absorption in WL consists of (1) the continuum of the BB transitions between (a) Ec (b) e-LH XL e-HH
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