Two-dimensional (2D) semiconductors are promising for photonic applications due to their exceptional optoelectronic properties, including large exciton binding energy, strong spin–orbit coupling, and potential integration with the standard complementary silicon-oxide-semiconductor (CMOS) technology. The dielectric environment can significantly affect the photoluminescence (PL) spectra of transition metal dichalcogenide (TMD) monolayers by modulating excitonic properties such as optical transitions and binding energies. Specifically, substrates with higher dielectric permittivity reduce exciton binding energy and the quasiparticle bandgap. Doping and the charge carrier concentration can further modify the emitted spectra by affecting the PL excitonic content. Increased doping can enhance trion formation and bandgap renormalization phenomena, leading to PL spectral shifts that depend on the semiconductor type. This study systematically investigates the substrate-induced dielectric screening, doping, and trapped charges in CVD-grown n-type 1L-WS₂ and p-type 1L-WSe₂ transferred onto CMOS-relevant SiO₂ and HfO₂ dielectrics. Our results show that p-type 1L-WSe₂ exhibits higher PL intensity and red-shifted trion emission on HfO₂, whereas n-type 1L-WS₂ shows a blue-shifted, lower-intensity PL for a similar dielectric environment. The difference arises from the interplay of the semiconductor type, doping, dielectric screening, and charge carrier concentration. We demonstrate that suspending the monolayers at the nanoscale enhances PL by reducing nonradiative recombination, enabling controlled micro-PL patterning and the formation of localized emission hot spots. Our results provide valuable insights for the development of next-generation CMOS-compatible optoelectronic devices.

We demonstrate Andreev pair injection across Nb-WS₂ junction evident as Andreev reflection in differential conductivity spectra below Nb critical temperature \({T}_{c}\). The superconducting- 2D semiconducting junction defined by a focused ion beam, shaped Nb pads, and semi-dry transfer of single layer CVD-grown WS₂ crystals ensured the mechanical integrity of the 2D TMD film, reduced contamination and defects at Nb-WS₂ junction, enabling the pristine study of the interface and facilitating Andreev pair injection. We observed enhanced conductivity in \({dI}/{dV}\) spectra for junction voltages smaller than the corresponding Nb superconducting gap, which vanishes as the device temperature is increased above the \({T}_{c}\). The position and the temperature dependence of the conductivity peaks suggest proximity effect-related phenomena explained by developed modified BTK theory. The presented results are crucial for the future implementation of proximity-based 2D hybrid devices including quantum light sources and superconducting field-effect transistors based on superconductor-semiconductor junctions.

Quantum nanophotonics offers essential tools and technologies for controlling quantum states, while maintaining a miniature form factor and high scalability. For example, nanophotonic platforms can transfer information from the traditional degrees of freedom (DoFs), such as spin angular momentum (SAM) and orbital angular momentum (OAM), to the DoFs of the nanophotonic platform - and back, opening new directions for quantum information processing. Recent experiments have utilized the total angular momentum (TAM) of a photon as a unique means to produce entangled qubits in nanophotonic platforms. Yet, the process of transferring the information between the free-space DoFs and the TAM was never investigated, and its implications are still unknown. Here, we reveal the evolution of quantum information in heralded single photons as they couple into and out of the near-field of a nanophotonic system. Through quantum state tomography, we discover that the TAM qubit in the near-field becomes a free-space qudit entangled in the photonic SAM and OAM. The extracted density matrix and Wigner function in free-space indicate state preparation fidelity above 97%. The concepts described here bring new concepts and methodologies in developing high-dimensional quantum circuitry on a chip.

For the successful implementation of organic electrochemical transistors in neuromorphic computing, bioelectronics, and real-time sensing applications it is essential to understand the factors that influence device switching times. This work describes a physical-electrochemical model of the transient response to a step of the gate voltage. The model incorporates 1) ion diffusion inside the channel that governs the electronic conductivity, 2) horizontal electron transport, and 3) the external elements (capacitance, ionic resistance) of the ion dynamics in the electrolyte. This work finds a general expression of two different time constants that determine the vertical insertion process in terms of the transport/polarization parameters, in addition to the electronic transit time. The work highlights the central role of the chemical capacitance in determining the modulation of the lateral conductivity. The different types of response of the drain current are classified, and the significance for synaptic operation in neuromorphic circuits is discussed. The model is confirmed by detailed simulations that enable to visualize the different ions distributions and dynamics.

The study of the net magneto-capacitance, C(B), in thin films of the conducting polymer Poly(3 4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is presented. In the films there are charged electrically-conducting PEDOT-rich regions surrounded by PSS insulating charged material. The high-conductivity grade PEDOT:PSS thin films are studied at low temperature, where the hopping conduction is dominant. It is experimentally observed that there is a finite net magneto-capacitance, C(B), in the temperature range T = 1.7–3 K. Thus, the observed C(B) is a direct evidence for an intra-site Coulomb interaction, U ≈ 2 meV, among the mobile charge carriers in the PEDOT-rich regions. The lifting of spin degeneracy motivates PEDOT for use in spintronic applications.

Fast-emitting scintillators are essential for advanced diagnostic techniques, yet many suffer from low radiation attenuation. This trade-off is particularly pronounced in polymer scintillators, which, despite their fast emission, exhibit low density and low atomic numbers, limiting the radiation attenuation factor, resulting in low detection efficiency. Here, we overcome this limitation by creating a heterostructure scintillator of alternating nanometric layers, combining fast light-emitting polymer scintillator layers and transparent stopping layers with a high radiation attenuation factor. The nanolayer thicknesses are tuned to optimize the penetration depth of recoil electrons in active emissive layers, maximizing the conversion of X-rays to visible light. This design increases light output by up to 1.5 times and enhances imaging resolution by a factor of 2 compared to homogeneous polymer scintillators due to the ability to use thinner samples. These results demonstrate the potential of heterostructure scintillators as next-generation detector materials, overcoming the limitations of homogeneous scintillators.

According to Noether’s theorem, symmetries in a physical system are intertwined with conserved quantities. These symmetries often determine the system topology, which is made ever more complex with increased dimensionality. Quasicrystals have neither translational nor global rotational symmetry, yet they intrinsically inhabit a higher-dimensional space in which symmetry resurfaces. Here, we discovered topological charge vectors in four dimensions (4D) that govern the real-space topology of 2D quasicrystals and reveal their inherent conservation laws. We demonstrate control over the topology in pentagonal plasmonic quasilattices, mapped by both phase-resolved and time-domain near-field microscopy, showing that their temporal evolution continuously tunes the 2D projections of their distinct 4D topologies. Our work provides a route to experimentally probe the thermodynamic properties of quasicrystals and topological physics in 4D and above.

The modulation of channel conductance in field-effect transistors (FETs) via metal-insulator-semiconductor structures has revolutionized information processing and storage. However, the limitations of silicon-based FETs in electrical switching have driven the search for new materials capable of overcoming these constraints. Electrostatic gating of competing electronic phases in a Mott material near its metal-to-insulator transition (MIT) offers the prospects of substantial modulation of the conducting electrons and electrical resistivity through small changes in band filling. While electrostatic control of the MIT has been previously reported, the advancement of Mott materials toward novel Mott-based transistors, MottFETs requires the realization of their unique physical properties in a solid-state device. In this study, we present gate control of electron correlation using a solid-state device utilizing the oxide Mott system La_1−xSr_xVO₃ as a correlated FET channel. We report on a gate resistance response that cannot be explained in a purely electrostatic framework. This behavior suggests an enhancement in effective mass and a reduction in effective carrier density as the system approaches its insulating state, consistent with theoretical predictions for Mott systems, suggesting at least 100× charge gain originating from the correlated behavior. These preliminary results pave the way toward the development of highly efficient, low-power electronic devices that could surpass the performance bottlenecks of conventional FETs by leveraging the electronic phase transitions of correlated electron systems.

Hyperbolic metasurfaces (HMSs) are artificially-engineered interfaces, exhibiting high anisotropy manifested as hyperbolic dispersion. Their ability to support extremely large momenta with negative diffraction and refraction places them as promising platforms for on-chip super-resolution and enhanced light-matter interaction. While the hyperbolic nature of these structures is experimentally demonstrated, only a limited number of studies have concentrated on their super-resolution capabilities, which are never obtained at visible-frequency for fully harnessing their immense resolution potential. Here, a near-field investigation of visible-frequency HMSs is presented, exploiting their super-resolution capabilities to their maximum potential. The impulse response of waves propagating across HMSs is measured and demonstrates deep sub-wavelength anomalous focusing and on-chip reflectionless negative refraction at the interface of parabolic and hyperbolic media, independent of incident angle. The approach lays the foundation for sub-wavelength imaging in 2D space for the advancement of imaging and wave compression devices, leveraging the capabilities of HMSs.

AbstractNanoparticles obtained by solid-state dewetting are known to exhibit an extraordinarily high mechanical strength under uniaxial compression. While most of such particles are single-crystalline, some may contain a coherent twin boundary (CTB) parallel to the substrate. The role of the CTB in the mechanical properties of such particles remained unknown. This work combines nano-mechanical testing, advanced characterization methods, and atomistic computer simulations to investigate the CTB effect of the mechanical behavior of Ni-Co nanoparticles produced by solid-state dewetting on a sapphire substrate. The results indicate that the CTB does not make any significant impact on the particle strength, toughness, solute softening, or strain hardening. These properties remain virtually the same as those of single-crystalline particles of the same alloy. The mechanisms of dislocation nucleation and the dislocation-CTB interactions are investigated in detail. The work lends additional confidence to the previous results for the mechanical behavior of nanoparticles produced by solid-state dewetting, some of which could have contained twin boundaries.