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- Brotons-Gisbert, Mauro, et al.
(author)
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Coulomb blockade in an atomically thin quantum dot coupled to a tunable Fermi reservoir
- 2019
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In: Nature Nanotechnology. - : NATURE PUBLISHING GROUP. - 1748-3387 .- 1748-3395. ; 14:5, s. 442-446
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Journal article (peer-reviewed)abstract
- Gate-tunable quantum-mechanical tunnelling of particles between a quantum confined state and a nearby Fermi reservoir of delocalized states has underpinned many advances in spintronics and solid-state quantum optics. The prototypical example is a semiconductor quantum dot separated from a gated contact by a tunnel barrier. This enables Coulomb blockade, the phenomenon whereby electrons or holes can be loaded one-by-one into a quantum dot(1,2). Depending on the tunnel-coupling strength(3,4), this capability facilitates single spin quantum bits(1,2,5) or coherent many-body interactions between the confined spin and the Fermi reservoirs(6,7). Van der Waals (vdW) heterostructures, in which a wide range of unique atomic layers can easily be combined, offer novel prospects to engineer coherent quantum confined spins(8,9), tunnel barriers down to the atomic limit(10) or a Fermi reservoir beyond the conventional flat density of states(11). However, gate-control of vdW nanostructuresu(12-16) at the single particle level is needed to unlock their potential. Here we report Coulomb blockade in a vdW heterostructure consisting of a transition metal dichalcogenide quantum dot coupled to a graphene contact through an atomically thin hexagonal boron nitride (hBN) tunnel barrier. Thanks to a tunable Fermi reservoir, we can deterministically load either a single electron or a single hole into the quantum dot. We observe hybrid excitons, composed of localized quantum dot states and delocalized continuum states, arising from ultra-strong spin-conserving tunnel coupling through the atomically thin tunnel barrier. Probing the charged excitons in applied magnetic fields, we observe large gyromagnetic ratios (similar to 8). Our results establish a foundation for engineering next-generation devices to investigate either novel regimes of Kondo physics or isolated quantum bits in a vdW heterostructure platform.
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| 2. |
- Brotons-Gisbert, Mauro, et al.
(author)
-
Out-of-plane orientation of luminescent excitons in two-dimensional indium selenide
- 2019
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 10
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Journal article (peer-reviewed)abstract
- Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution of bulk InSe and two-dimensional InSe, WSe2 and MoSe2. We demonstrate, with the support of ab-initio calculations, that layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation, in contrast with the in-plane orientation of dipoles we find in two-dimensional WSe2 and MoSe2 at room-temperature. These results, combined with the high tunability of the optical response and outstanding transport properties, position layered InSe as a promising semiconductor for novel optoelectronic devices, in particular for hybrid integrated photonic chips which exploit the out-of-plane dipole orientation.
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