We have demonstrated laser cooling of a single electron spin trapped in semiconductor quantum dot. Optical coupling electronic states was achieved using resonant excitation the charged dot (trion) transitions along with heavy-light hole mixing, which leads to weak yet finite rates for spin-flip Raman scattering. With this mechanism, can be cooled from 4.2 0.020 kelvin, as confirmed by strength induced Pauli blockade trion absorption. Within framework information processing, corresponds...

The mesoscopic spin system formed by the 10E4-10E6 nuclear spins in a semiconductor quantum dot offers unique setting for study of many-body physics condensed matter. dynamics this and its coupling to electron is fundamentally different from bulk counter-part as well that atoms due increased fluctuations result reduced dimensions. In recent years, interest studying systems their confined has been fueled direct implication possible applications such information processing fascinating...

Moiré effects in vertical stacks of two-dimensional crystals give rise to new quantum materials with rich transport and optical phenomena that originate from modulations atomic registries within moiré supercells. Due finite elasticity, however, the superlattices can transform moiré-type periodically reconstructed patterns. Here we expand notion such nanoscale lattice reconstruction mesoscopic scale laterally extended samples demonstrate consequences studies excitons MoSe2-WSe2...

Interlayer excitons in van der Waals heterostructures diffuse rapidly, with diffusion coefficients about 1000 times larger than previously seen, the absence of moir\'e- and disorder-induced localization.

We report the first observation of photon antibunching in photoluminescence from single carbon nanotubes. The emergence a fast luminescence decay component under strong optical excitation indicates that Auger processes are partially responsible for inhibiting two-photon generation. Additionally, presence exciton localization at low temperatures ensures nanotubes emit photons predominantly one by one. fact multiphoton emission probability can be smaller than 5% suggests could used as source...

We show how the optical properties of a single semiconductor quantum dot can be controlled with small dc voltage applied to gate electrode. find that transmission spectrum neutral exciton exhibits two narrow lines $\sim 2$ $\mu$eV linewidth. The splitting into linearly polarized components arises through an exchange interaction within exciton. turned off by choosing where is occupied additional electron. Saturation spectroscopy demonstrates behaves as two-level system. Our experiments...

The fine structure of the neutral exciton in a single self-assembled InGaAs quantum dot is investigated under effect an applied uniaxial stress. spectrum excitonic Rayleigh scattering was measured reflectivity using high-resolution laser spectroscopy while sample submitted to tunable stress along its [110] crystal axis. We show that this stretching technique, potential elastically deformable such splitting can be substantially reduced.

Conditional quantum dynamics, where the state of one system controls outcome measurements on another system, is at heart information processing. We demonstrate conditional dynamics for two coupled dots, whereby probability that dot makes a transition to an optically excited controlled by presence or absence optical excitation in neighboring dot. Interaction between dots mediated tunnel coupling states and can be gated applying laser field right frequency. Our results represent substantial...

We report on a quantitative measurement of the spatial coherence electrons emitted from sharp metal needle tip. investigate in photoemission triggered by near-ultraviolet laser with photon energy 3.1 eV and compare it to dc-field emission. A carbon nanotube is brought into close proximity emitter tip act as an electrostatic biprism. From resulting electron matter wave interference fringes, we deduce upper limit effective source radius both laser-triggered emission mode, which quantifies...

Coherent energy exchange between plasmons and excitons is a phenomenon that arises in the strong coupling regime resulting distinct hybrid states. The DNA-origami technique provides an ideal framework to custom-tune plasmon-exciton nanostructures. By employing this well controlled self-assembly process, we realized states by precisely positioning metallic nanoparticles defined spatial arrangement with fixed nanometer-sized interparticle spacing. Varying nanoparticle diameter 30 nm 60 while...

Monolayer transition metal dichalcogenides (TMDs) undergo substantial changes in the single-particle band structure and excitonic optical response upon addition of just one layer. As opposed to single-layer limit, bandgap bilayer (BL) TMD semiconductors is indirect which results reduced photoluminescence with richly structured spectra that have eluded a detailed understanding date. Here, we provide closed interpretation cryogenic emission from BL WSe2 as representative material for wider...

A direct band gap, remarkable light-matter coupling as well strong spin-orbit and Coulomb interaction establish two-dimensional (2D) crystals of transition metal dichalcogenides (TMDs) an emerging material class for fundamental studies novel technological concepts. Valley selective optical excitation allows optoelectronic applications based on the momentum excitons. In addition to lattice imperfections disorder, scattering by phonons is a significant mechanism valley depolarization...

The optical properties of monolayer and bilayer transition metal dichalcogenide semiconductors are governed by excitons in different spin valley configurations, providing versatile aspects for van der Waals heterostructures devices. We present experimental theoretical studies exciton energy splittings external magnetic field neutral charged WSe$_2$ crystals embedded a effect device active doping control. develop methods to calculate the $g$-factors from first principles tight-binding all...

Abstract Monolayer transition metal dichalcogenides integrated in optical microcavities host exciton-polaritons as a hallmark of the strong light-matter coupling regime. Analogous concepts for hybrid systems employing spatially indirect excitons with permanent electric dipole moment heterobilayer crystals promise realizations exciton-polariton gases and condensates inherent dipolar interactions. Here, we implement cavity-control interlayer vertical MoSe 2 -WSe heterostructures. Our...

Abstract The controlled functionalization of single-walled carbon nanotubes with luminescent sp 3 -defects has created the potential to employ them as quantum-light sources in near-infrared. For that, it is crucial control their spectral diversity. emission wavelength determined by binding configuration defects rather than molecular structure attached groups. However, current methods produce a variety configurations and thus wavelengths. We introduce simple reaction protocol for creation...

Layered two-dimensional materials exhibit rich transport and optical phenomena in twisted or lattice-incommensurate heterostructures with spatial variations of interlayer hybridization arising from moir\'e interference effects. Here, we report experimental theoretical studies excitons heterobilayers heterotrilayers transition metal dichalcogenides. Using MoSe$_2$-WSe$_2$ stacks as representative realizations van der Waals bilayer trilayer heterostructures, observe contrasting signatures...

Abstract Magnetism in two-dimensional materials reveals phenomena distinct from bulk magnetic crystals, with sensitivity to charge doping and electric fields monolayer bilayer van der Waals magnet CrI 3 . Within the class of layered magnets, semiconducting CrSBr stands out by featuring stability under ambient conditions, correlating excitons order thus providing strong magnon-exciton coupling, exhibiting peculiar magneto-optics exciton-polaritons. Here, we demonstrate that both exciton...

$\mathrm{MoT}{\mathrm{e}}_{2}$ belongs to the semiconducting transition-metal dichalcogenide family with certain properties differing from other well-studied members $(\mathrm{Mo},\mathrm{W}){(\mathrm{S},\mathrm{Se})}_{2}$. The optical band gap is in near-infrared region, and both monolayers bilayers may have a direct gap. We first simulate single-particle structure of monolayer bilayer density-functional-theory-$GW$ calculations. find (indirect) electronic for (bilayer). By solving addition...

As a step toward deterministic and scalable assembly of ordered spin arrays we here demonstrate bottom-up approach to position fluorescent nanodiamonds (NDs) with nanometer precision on DNA origami structures. We have realized reliable broadly applicable surface modification strategy that results in DNA-functionalized perfectly dispersed NDs were then self-assembled predefined geometries. With optical studies show the fluorescence properties nitrogen-vacancy color centers are preserved...

Abstract Raman spectroscopy reveals chemically specific information and provides label-free insight into the molecular world. However, signals are intrinsically weak call for enhancement techniques. Here, we demonstrate Purcell of scattering in a tunable high-finesse microcavity, utilize it diagnostics by combined absorption imaging. Studying individual single-wall carbon nanotubes, identify crucial structural parameters such as nanotube radius, electronic structure extinction cross-section....

Laser modulation spectroscopy on a MoSe${}_{2}$/WS${}_{2}$ heterostructure shows an intricate interplay of both intra- and interlayer moir\'e excitons allows to determine unambiguously the nature observed optical resonances.