State Expansion of a Levitated Nanoparticle in a Dark Harmonic Potential.

We spatially expand and subsequently contract the motional thermal state of a levitated nanoparticle using a hybrid trapping scheme. The particle's center-of-mass motion is initialized in a thermal state (temperature 155 mK) in an optical trap and then expanded by subsequent evolution in a much softer Paul trap in the absence of optical fields. We demonstrate expansion of the motional state's standard deviation in position by a factor of 24.

Bulk-suppressed and surface-sensitive Raman scattering by transferable plasmonic membranes with irregular slot-shaped nanopores.

Raman spectroscopy enables the non-destructive characterization of chemical composition, crystallinity, defects, or strain in countless materials. However, the Raman response of surfaces or thin films is often weak and obscured by dominant bulk signals. Here we overcome this limitation by placing a transferable porous gold membrane, (PAuM) on the surface of interest.

Cavity-mediated long-range interactions in levitated optomechanics.

The ability to engineer cavity-mediated interactions has emerged as a powerful tool for the generation of non-local correlations and the investigation of non-equilibrium phenomena in many-body systems. Levitated optomechanical systems have recently entered the multiparticle regime, which promises the use of arrays of strongly coupled massive oscillators to explore complex interacting systems and sensing. Here we demonstrate programmable cavity-mediated interactions between nanoparticles in vacuum by combining advances in multiparticle optical levitation and cavity-based quantum control.

Overbias Photon Emission from Light-Emitting Devices Based on Monolayer Transition Metal Dichalcogenides.

Tunneling light-emitting devices (LEDs) based on transition metal dichalcogenides (TMDs) and other two-dimensional (2D) materials are a new platform for on-chip optoelectronic integration. Some of the physical processes underlying this LED architecture are not fully understood, especially the emission at photon energies higher than the applied electrostatic potential, so-called overbias emission. Here we report overbias emission for potentials that are near half of the optical bandgap energy in TMD-based tunneling LEDs.

THE HEALTH SYSTEM OF THE FIRST CZECHOSLOVAK REPUBLIC AND ITS ROLE IN COMBATING CONTAGIOUS DISEASES IMMEDIATELY AFTER THE FIRST WORLD WAR (THE 1920s).

A complex epidemiological situation marked the health system at the time of the establishment of the Czechoslovak Republic. Reducing the number of infectious diseases was an essential task of the State Administration of Health. It required new legislation and various steps directed at reducing infectious diseases.

Exciton-assisted electron tunnelling in van der Waals heterostructures.

The control of elastic and inelastic electron tunnelling relies on materials with well-defined interfaces. Two-dimensional van der Waals materials are an excellent platform for such studies. Signatures of acoustic phonons and defect states have been observed in current-to-voltage measurements.

WSe Light-Emitting Device Coupled to an h-BN Waveguide.

Optical information processing using photonic integrated circuits is a key goal in the field of nanophotonics. Extensive research efforts have led to remarkable progress in integrating active and passive device functionalities within one single photonic circuit. Still, to date, one of the central components, i.

Scalable all-optical cold damping of levitated nanoparticles.

Motional control of levitated nanoparticles relies on either autonomous feedback via a cavity or measurement-based feedback via external forces. Recent demonstrations of the measurement-based ground-state cooling of a single nanoparticle employ linear velocity feedback, also called cold damping, and require the use of electrostatic forces on charged particles via external electrodes. Here we introduce an all-optical cold damping scheme based on the spatial modulation of trap position, which has the advantage of being scalable to multiple particles.

Molecular Encapsulation from the Liquid Phase and Graphene Nanoribbon Growth in Carbon Nanotubes.

Growing graphene nanoribbons from small organic molecules encapsulated in carbon nanotubes can result in products with uniform width and chirality. We propose a method based on encapsulation of 1,2,4-trichlorobenzene from the liquid phase and subsequent annealing. This procedure results in graphene nanoribbons several tens of nanometers long.

Encoding information in the mutual coherence of spatially separated light beams.

Coherence has been used as a resource for optical communications since its earliest days. It is widely used for the multiplexing of data, but not for the encoding of data. Here we introduce a coding scheme, which we call mutual coherence coding, to encode information in the mutual coherence of spatially separated light beams.

Ponderomotive Squeezing of Light by a Levitated Nanoparticle in Free Space.

A mechanically compliant element can be set into motion by the interaction with light. In turn, this light-driven motion can give rise to ponderomotive correlations in the electromagnetic field. In optomechanical systems, cavities are often employed to enhance these correlations up to the point where they generate quantum squeezing of light.

Moving across Borders: The Work Life Experiences of Czech Cross-border Workers during the COVID-19 Pandemic.

The experiences of cross-border workers (CBWs) and the difficulties they face during the ongoing COVID-19 pandemic have been neglected in previous research. CBWs experience various stressors under normal circumstances, where they are often subjected to unequal working conditions and forced to transition between two different societies. The measures that were introduced in response to the COVID-19 pandemic, including the implementation of physical borders, further worsened the situation for these individuals.

Tip-Enhanced Stokes-Anti-Stokes Scattering from Carbyne.

Carbyne, a linear chain of carbon atoms, is the truly one-dimensional allotrope of carbon and the strongest known Raman scatterer. Here, we use tip-enhanced Raman scattering (TERS) to further enhance the Raman response of a single carbyne chain confined inside a double-walled carbon nanotube. We observe an increase of the anti-Stokes scattering by a factor of 3290 and a 22-fold enhancement of the anti-Stokes/Stokes ratio relative to far-field measurements.

Freestanding and Permeable Nanoporous Gold Membranes for Surface-Enhanced Raman Scattering.

Surface-enhanced Raman spectroscopy (SERS) demands reliable, high-enhancement substrates in order to be used in different fields of application. Here we introduce freestanding porous gold membranes (PAuM) as easy-to-produce, scalable, mechanically stable, and effective SERS substrates. We fabricate large-scale sub-30 nm thick PAuM that form freestanding membranes with varying morphologies depending on the nominal gold thickness.

Tip-enhanced Raman spectroscopy of confined carbon chains.

Long linear chains of carbon encapsulated in carbon nanotubes represent the finite realization of carbyne, the truly one-dimensional carbon allotrope. Driven by advances in the synthesis of such structures, carbyne has attracted significant interest in recent years, with numerous experimental studies exploring its remarkable properties. As for other carbon nanomaterials, Raman spectroscopy has played an important role in the characterization of carbyne.

Kovacs Memory Effect with an Optically Levitated Nanoparticle.

The understanding of the dynamics of nonequilibrium cooling and heating processes at the nanoscale is still an open problem. These processes can follow surprising relaxation paths due to, e.g.

Resonant Light Emission from Graphene/Hexagonal Boron Nitride/Graphene Tunnel Junctions.

Single-layer graphene has many remarkable properties but does not lend itself as a material for light-emitting devices as a result of its lack of a band gap. This limitation can be overcome by a controlled stacking of graphene layers. Exploiting the unique Dirac cone band structure of graphene, we demonstrate twist-controlled resonant light emission from graphene/hexagonal boron nitride (h-BN)/graphene tunnel junctions.

Sub-Kelvin Feedback Cooling and Heating Dynamics of an Optically Levitated Librator.

Rotational optomechanics strives to gain quantum control over mechanical rotors by harnessing the interaction of light and matter. We optically trap a dielectric nanodumbbell in a linearly polarized laser field, where the dumbbell represents a nanomechanical librator. Using measurement-based parametric feedback control in high vacuum, we cool this librator from room temperature to 240 mK and investigate its heating dynamics when released from feedback.

Quantum control of a nanoparticle optically levitated in cryogenic free space.

Tests of quantum mechanics on a macroscopic scale require extreme control over mechanical motion and its decoherence. Quantum control of mechanical motion has been achieved by engineering the radiation-pressure coupling between a micromechanical oscillator and the electromagnetic field in a resonator. Furthermore, measurement-based feedback control relying on cavity-enhanced detection schemes has been used to cool micromechanical oscillators to their quantum ground states.

Anti-Stokes Raman Scattering of Single Carbyne Chains.

We investigate the anti-Stokes Raman scattering of single carbyne chains confined inside double-walled carbon nanotubes. Individual chains are identified using tip-enhanced Raman scattering (TERS) and heated by resonant excitation with varying laser powers. We study the temperature dependence of carbyne's Raman spectrum and quantify the laser-induced heating based on the anti-Stokes/Stokes ratio.

Erratum: GHz Rotation of an Optically Trapped Nanoparticle in Vacuum [Phys. Rev. Lett. 121, 033602 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.121.