Experimental Realization Research Articles

Challenges and advantages of cut solar cells for shingling and half-cell modules

Cutting silicon solar cells from their host wafer into smaller cells reduces the output current per cut cell and therefore allows for reduced ohmic losses in series interconnection at module level. This comes with a trade-off of unpassivated cutting edges, which result in power losses. This performance drop can be seen in fill factor FF and open-circuit voltage VOC losses on cut cell level. Based on experimental realization of different solar cell layouts on the same industrial blue wafers (solar cell precursors), a combined simulation method to predict the performance on module level is demonstrated. This method uses Gridmaster+ for cell simulation and SmartCalc. Module for module simulation. The accuracy of the simulations is demonstrated by comparing with experimental results both from host and cut cell level. In addition, significant influence of the current–voltage (I–V) measurement configuration is demonstrated, mainly affecting FF. Using flexible methods like GridTOUCH® for I–V testing gives fast results but can also lead to overestimation of the host cell performance, resulting in overestimated cell-to-module losses or unreasonable comparisons between hosts and cut cells. It is also demonstrated that application of the passivated edge technology (PET) yields I–V characteristics close to those of cells with ideal edges, i.e., without edge recombination. The implications on the module efficiency are also compared between modules built using cells with and without edge passivation, giving the highest efficiency for a shingled module with PET.

An educational model of the Deutsch algorithm for secondary school

In this paper, we present the outline of an educational path to introduce a crucial historical turnpoint of quantum information research—namely the Deutsch algorithm—to secondary school students. We discuss a basic elementarization strategy allowing students to single out and focus on the individual features of quantum mechanics involved in the different steps of the algorithm information processing phase, which can potentially be useful for the educational reconstruction of other algorithms and protocols. The sequence includes the experimental realization on the optical bench of an analogue of the Deutsch algorithm, working with classical coherent light. The educational path was tested both in curricular and out-of-school settings, and preliminary results will be discussed.

Nanodevice simulations and electronic transport properties of a two-dimensional PbBr2 monolayer

Two-dimensional (2D) wide bandgap semiconductors are promising blocks for applications in photodetections, spintronics and high energy radiation detection. Here, we probe the mechanical, biaxial strain-relate, electronic transport, and optoelectronic properties of PbBr2 monolayer with wide bandgaps using first-principles calculations. The 2D Young's modulus of PbBr2 monolayer is determined to be 14.68 N m−1 and the shear modulus is calculated to be 5.83 N m−1 at 300 K, revealing that PbBr2 monolayer is mechanically more flexible than other 2D materials, such as hexagonal-BN and MoB2. Interestingly, a specific forbidden bandwidth can be obtained by implementing a suitable strain on PbBr2 monolayer, and such effect leads to indirect bandgap semiconductor properties. Furthermore, various PbBr2 monolayer nanodevices, including p-n junction diodes, p-i-n junction field-effect transistors (FETs), and phototransistors, are designed and explored to investigate their transport properties. A variety of excellent transport properties, including prominent unidirectional transport, remarkable electrical anisotropy, obvious field-effect property, strong photoelectric response, and prominent absorption characteristics in the ultraviolet region, have been observed in these nanodevices. Our results unveil the multifunctional nature and superior performance of PbBr2 monolayer and suggest a practical configuration for the experimental realization in next-generation semiconductor nanodevices.

Simultaneously enhanced magnomechanical cooling and entanglement assisted by an auxiliary microwave cavity.

We propose a mechanism to simultaneously enhance quantum cooling and entanglement via coupling an auxiliary microwave cavity to a magnomechanical cavity. The auxiliary cavity acts as a dissipative cold reservoir that can efficiently cool multiple localized modes in the primary system via beam-splitter interactions, which enables us to obtain strong quantum cooling and entanglement. We analyze the stability of the system and determine the optimal parameter regime for cooling and entanglement under the auxiliary-microwave-cavity-assisted (AMCA) scheme. The maximum cooling enhancement rate of the magnon mode can reach 98.53%, which clearly reveals that the magnomechanical cooling is significantly improved in the presence of the AMCA. More importantly, the dual-mode entanglement of the system can also be significantly enhanced by AMCA in the full parameter region, where the initial magnon-phonon entanglement can be maximally enhanced by a factor of about 11. Another important result of the AMCA is that it also increases the robustness of the entanglement against temperature. Our approach provides a promising platform for the experimental realization of entanglement and quantum information processing based on cavity magnomechanics.

Strain-Induced Reversible Motion of Skyrmions at Room Temperature.

Magnetic skyrmions are topologically protected swirling spin textures with great potential for future spintronic applications. The ability to induce skyrmion motion using mechanical strain not only stimulates the exploration of exotic physics but also affords the opportunity to develop energy-efficient spintronic devices. However, the experimental realization of strain-driven skyrmion motion remains a formidable challenge. Herein, we demonstrate that the inhomogeneous uniaxial compressive strain can induce the movement of isolated skyrmions from regions of high strain to regions of low strain at room temperature, which was directly observed using an in situ Lorentz transmission electron microscope with a specially designed nanoindentation holder. We discover that the uniaxial compressive strain can transform skyrmions into a single domain with in-plane magnetization, resulting in the coexistence of skyrmions with a single domain along the direction of the strain gradient. Through comprehensive micromagnetic simulations, we reveal that the repulsive interactions between skyrmions and the single domain serve as the driving force behind the skyrmion motion. The precise control of skyrmion motion through strain provides exciting opportunities for designing advanced spintronic devices that leverage the intricate interplay between strain and magnetism.

Moiré synaptic transistor with room-temperature neuromorphic functionality.

Moiré quantum materials host exotic electronic phenomena through enhanced internal Coulomb interactions in twisted two-dimensional heterostructures1-4. When combined with the exceptionally high electrostatic control in atomically thin materials5-8, moiré heterostructures have the potential to enable next-generation electronic devices with unprecedented functionality. However, despite extensive exploration, moiré electronic phenomena have thus far been limited to impractically low cryogenic temperatures9-14, thus precluding real-world applications of moiré quantum materials. Here we report the experimental realization and room-temperature operation of a low-power (20 pW) moiré synaptic transistor based on an asymmetric bilayer graphene/hexagonal boron nitride moiré heterostructure. The asymmetric moiré potential gives rise to robust electronic ratchet states, which enable hysteretic, non-volatile injection of charge carriers that control the conductance of the device. The asymmetric gating in dual-gated moiré heterostructures realizes diverse biorealistic neuromorphic functionalities, such as reconfigurable synaptic responses, spatiotemporal-based tempotrons and Bienenstock-Cooper-Munro input-specific adaptation. In this manner, the moiré synaptic transistor enables efficient compute-in-memory designs and edge hardware accelerators for artificial intelligence and machine learning.

Structural, Electronic and Magnetic Properties of Silicene Functionalized with 4d TM Atoms

The experimental realization of silicene has ignited a great deal of interest in researching its properties for utilization in device applications. Silicene is composed of a lattice of silicon. As a result, it can be integrated with contemporary circuitry structures, which are predominantly silicon-based. Therefore, investigating its characteristics, especially those of the bandgap, is pivotal. In the present work, the density functional theory approach is employed to examine the structural, electronic and magnetic characteristics of free-standing silicene doped with 4d Transition Metal (TM) atoms. Modelling is done for a 4x4 silicene supercell with a single vacancy. The resulting structure is, thus, doped with 4d transition metal atoms. Doping results in lattice distortion, as evidenced by the variance in Si-TM bond length relative to Si-Si bond length. The shortest bond length is noticed in the instance of Ru doping, thus demonstrating its strongest bonding with Si atoms. Doping causes the structure to become increasingly deformed, as proved by the elevation in buckling height as well. Except for Zr, Ru and Pd, which exhibit semiconductor behaviour, the 4d TM doping in silicene results in metallic characteristics as the bands cross the Fermi level in the majority of the configurations discussed here. A narrow band gap with a range of 2.1 to 252 meV is produced by doping silicene with Zr, Ru, and Pd. Magnetism is demonstrated by Nb, Mo, Tc, and Rh-doped structures, whereas the other structures are nonmagnetic. The presence of magnetism in these structures is primarily due to contributions from Si-3p, TM- 4d/5s orbitals, and their hybridization.

On readout and initialisation fidelity by finite demolition single shot readout

Abstract Ideal projective quantum measurement makes the system state collapse in one of the observable operator eigenstates | ϕ α ⟩ , making it a powerful tool for preparing the system in the desired pure state. Nevertheless, experimental realisations of projective measurement are not ideal. During the measurement time needed to overcome the classical noise of the apparatus, the system state is often (slightly) perturbed, which compromises the fidelity of initialisation. In this paper, we propose an analytical model to analyse the initialisation fidelity of the system performed by the single-shot readout. We derive a method to optimise parameters for the three most used cases of photon counting based readouts for NV colour centre in diamond, charge state, nuclear spin and low temperature electron spin readout. Our work is of relevance for the accurate description of initialisation fidelity of the quantum bit when the single-shot readout is used for initialisation via post-selection or real-time control.

Design and experimental realization of multifunctional anisotropic metasurface for efficient polarization manipulation in microwave frequencies

This paper presents the realization of a multifunction anisotropic metasurface capable of operating as both a half-waveplate and a quarter-waveplate in the C, X, and Ku bands. The numerical and experimental results demonstrate the metasurface is able to convert linear and circular polarizations to their respective cross-polarizations, as well as achieve linear-to-circular and circular-to-linear polarization conversions in the microwave frequency regime. Notably, the metasurface maintains high conversion efficiencies for both half-wave and quarter-wave plate operations, even when subjected to variations in the incidence angle. The underlying physical mechanism is elucidated through the analysis of eigen values, surface current distribution and the retrieval of effective physical parameters. The proposed metasurface is useful for communication and polarization manipulation devices due to its simple construction, compact size, angular stability, and multi-functionality.

Shifty invisibility cloaks.

We recently presented what we believe are new cloaking strategies [Bělín et al., Opt. Express27, 37327 (2019)10.1364/OE.27.037327], abstracted from the properties of an ideal-lens cloak that exists in theory only. Key to the cloaking strategies is that objects on the cloak's inside are imaged to its outside. In the simplest case, interior objects appear simply shifted, forming a "shifty cloak". Here we connect our work to several previous investigations of shifty cloaks and other shifty devices, designed using standard transformation optics, thereby bringing our cloaking strategies closer to experimental realization. We investigate to the best of our knowledge novel combinations of shifty cloaks, specifically Janus devices and optical wormholes. Finally, we demonstrate an experimental realization of a paraxial shifty cloak.

Multi-layered cladding based ultra-low loss, single mode antiresonant hollow core fibers

In reality, an efficient platform for high-power laser delivery is highly important, which can be justified by readily available fiber lasers, and hollow-core fiber can be the best platform for guiding high optical power over long distances. The constraints include designing new cladding geometry, which may lead to a higher laser induced damage threshold in the fiber’s structure, having low losses along with a single mode nature. This article reports a new antiresonant fiber that has a hollow core and a triple-layered cladding configuration with only circular tube elements. The effects of multiple layers corresponding to the number of tube rings in the cladding geometry are well explored, which leads to understanding the physical insight of inter-layers. In comparison to double-layered cladding elements fiber, the proposed fiber significantly reduces loss by an order of two and reveals a minimum leakage loss of 5.82 × 10−5 dB/km at the chosen wavelength of 1.06 µm through the proper arrangement of cladding elements. We achieved a maximal higher order mode extinction ratio of about 104 (indicates the excellent single mode properties) and comparatively a little bending-induced loss of 9.00 × 10−4 dB/km, when the radius of bending is 14 cm. As a result, our studies on new multilayer fiber designs are not only useful for delivering high laser power but also serve as guidelines for the experimental realization of future multilayered cladding fibers.

Bragg gratings with novel waveguide models fabricated in bulk glass via fs-laser writing and their slow-light effects.

We present the experimental realization of an innovative parallel partially overlapping waveguides (PO-WGs) model grounded in the thermal accumulated regime and fabricated using femtosecond (fs) laser direct-writing within low-iron bulk glass. The 75mm long novel PO-WGs model was made by partially overlapping the shell parts of two core-shell types of waveguides via a back-and-forth single pass fs-laser inscription. The detailed evolution of the PO-WGs model from inception to completion was offered, accompanying by a thorough characterization, which unveils a substantial refractive index (RI) change, on the order of 10-3, alongside low propagation loss (0.2 dB/cm) and distinctive features associated with the single mode and shell-guided light. Notably, the unsaturated performance of PO-WGs model after the primary inscription paves the way for potential applications in the successful creation of two distinctive types of Bragg gratings: first-order dot-Bragg grating and second-order line-Bragg grating. The 75 mm long dot-Bragg grating was written by a periodic dot array with a height of 6 µm atop the PO-WGs, and the birefringence was measured of 1.5 × 10-5 with a 16 pm birefringence-induced wavelength difference. The line-Bragg grating, which was inscribed with dual PO-WGs extending the line grating part to 40 mm in length along its period for increasing the transmission dip, exhibits a pronounced polarization dependence showcasing an effective birefringence of 4.2 × 10-4 at the birefringence-induced wavelength difference of 0.45 nm. We delved into the slow-light effects of the two Bragg gratings thoroughly, which the theoretical analysis revealed an effective group delay of 0.58 ns (group index 2.3) for the dot-Bragg grating. Similarly, the line-Bragg grating exhibited an effective group delay of 0.3 ns (group index 2.3), in good agreement with experimental measurements. These findings underscore the exciting potential of our gratings for creating optical slow-wave structures, particularly for future on-chip applications.

Extremely large magnetoresistance and non-trivial band topology in YSb semimetal

The topologically protected states in a material lead to the occurrence of spectacular properties like massless fermions, high carrier mobility, extremely large magnetoresistance (XMR) and nontrivial Berry phase. In this context, we report the experimental realization of non-trivial band topology and nonsaturating XMR at low temperatures in a rock-salt type rare-earth monopnictide YSb semimetal which is ∼ two million percent at 2 K and 9 T. The Hall resistivity and Shubnikov-de Hass (SdH) oscillations confirm the multiband character of YSb crystal along with high carrier mobility. The analysis of SdH oscillations reveal a π-Berry phase for the α-band, indicating the non-trivial band topology in YSb. This non-trivial band topology is further confirmed by the observation of the topologically protected state, which is demonstrated by a high transport lifetime (τtr) to the quantum lifetime (τq) ratio, r = τtrτq = 300 times. The topological protection results in a very low zero-field resistivity at low temperatures. Here, we show that the topological protection mechanism, charge compensation and high carrier mobility are the key factors for obtaining XMR in YSb crystal.

Natural language processing in assistive technologies

Natural language processing expanded in the last 30 years, arising to cover a wide range of applications in various domains, among them assistive technologies, helping people with disabilities due to accidents, aging, or genetic heritance, to enhance their social integration and their daily life. The growing need in assistive techniques has led to the involvement in the usual devices of intelligent modules to improve and facilitate their use, natural language processing attaining nowadays a high applicability in this domain. The paper discusses first basic methodologies involved in natural language processing like speech recognition, speech synthesis and text processing. Some possible applications are then presented with accent on experimental realization of intelligent modules for assistive devices in the laboratory of our university.

Three-Wave Mixing of Dipole Solitons in One-Dimensional Quasi-Phase-Matched Nonlinear Crystals

A quasi-phase-matched technique is introduced for soliton transmission in a quadratic [χ (2)] nonlinear crystal to realize the stable transmission of dipole solitons in a one-dimensional space under three-wave mixing. We report four types of solitons as dipole solitons with distances between their bimodal peaks that can be laid out in different stripes. We study three cases of these solitons: spaced three stripes apart, one stripe apart, and confined to the same stripe. For the case of three stripes apart, all four types have stable results, but for the case of one stripe apart, stable solutions can only be found at ω 1 = ω 2, and for the condition of dipole solitons confined to one stripe, stable solutions exist only for Type1 and Type3 at ω 1=ω 2. The stability of the soliton solution is solved and verified using the imaginary time propagation method and real-time transfer propagation, and soliton solutions are shown to exist in the multistability case. In addition, the relations of the transportation characteristics of the dipole soliton and the modulation parameters are numerically investigated. Finally, possible approaches for the experimental realization of the solitons are outlined.

Quantum spin nematic phase in a square-lattice iridate.

Spin nematic is a magnetic analogue of classical liquid crystals, a fourth state of matter exhibiting characteristics of both liquid and solid1,2. Particularly intriguing is a valence-bond spin nematic3-5, in which spins are quantum entangled to form a multipolar order without breaking time-reversal symmetry, but its unambiguous experimental realization remains elusive. Here we establish a spin nematic phase in the square-lattice iridate Sr2IrO4, which approximately realizes a pseudospin one-half Heisenberg antiferromagnet in the strong spin-orbit coupling limit6-9. Upon cooling, the transition into the spin nematic phase at TC ≈ 263 K is marked by a divergence in the static spin quadrupole susceptibility extracted from our Raman spectra and concomitant emergence of a collective mode associated with the spontaneous breaking of rotational symmetries. The quadrupolar order persists in the antiferromagnetic phase below TN ≈ 230 K and becomes directly observable through its interference with the antiferromagnetic order in resonant X-ray diffraction, which allows us to uniquely determine its spatial structure. Further, we find using resonant inelastic X-ray scattering a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state10,11. Taken together, our results reveal a quantum order underlying the Néel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity12,13.

Approximating complex 3D curves using origami spring structures

Origami provides a versatile platform for creating intricate three-dimensional (3D) reconfigurable structures through folding techniques. However, the applications of origami patterns are restricted due to limited deformation modes and complex actuation. Here we explore origami spring structures as a solution to address these limitations by approximating complex 3D curves with an underactuated scheme. By doing so, we showcase the reconfigurability and versatility of origami springs while tackling control complexity. Through the introduction of virtual creases, we simplify non-rigid deformations and enable accurate descriptions of their 3D configurations. Furthermore, we develop inverse kinematics optimization algorithms to determine optimal configurations closely approximating given 3D curves with full actuation and underactuated situations. Experimental realization of various 3D curves demonstrates the feasibility and effectiveness of our proposed approach. This research could find practical utility in soft robotics, flexible mechanisms, and deployable structures.

Collective radiative interactions in the discrete truncated Wigner approximation

Interfaces of light and matter serve as a platform for exciting many-body physics and photonic quantum technologies. Due to the recent experimental realization of atomic arrays at sub-wavelength spacings, collective interaction effects such as superradiance have regained substantial interest. Their analytical and numerical treatment is however quite challenging. Here we develop a semiclassical approach to this problem that allows to describe the coherent and dissipative many-body dynamics of interacting spins while taking into account lowest-order quantum fluctuations. For this purpose we extend the discrete truncated Wigner approximation, originally developed for unitarily coupled spins, to include collective, dissipative spin processes by means of truncated correspondence rules. This maps the dynamics of the atomic ensemble onto a set of semiclassical, numerically inexpensive stochastic differential equations. We benchmark our method with exact results for the case of Dicke decay, which shows excellent agreement. For small arrays we compare to exact simulations, again showing good agreement at early times and at moderate to strong driving, and to a second order cumulant expansion. We conclude by studying the radiative properties of a spatially extended three-dimensional, coherently driven gas and compare the coherence of the emitted light to experimental results.

Experimental Realization of Stable Exceptional Chains Protected by Non-Hermitian Latent Symmetries Unique to Mechanical Systems.

Lines of exceptional points are robust in the three-dimensional non-Hermitian parameter space without requiring any symmetry. However, when more elaborate exceptional structures are considered, the role of symmetry becomes critical. One such case is the exceptional chain (EC), which is formed by the intersection or osculation of multiple exceptional lines (ELs). In this Letter, we investigate a non-Hermitian classical mechanical system and reveal that a symmetry intrinsic to second-order dynamical equations, in combination with the source-free principle of ELs, guarantees the emergence of ECs. This symmetry can be understood as a non-Hermitian generalized latent symmetry, which is absent in prevailing formalisms rooted in first-order Schrödinger-like equations and has largely been overlooked so far. We experimentally confirm and characterize the ECs using an active mechanical oscillator system. Moreover, by measuring eigenvalue braiding around the ELs meeting at a chain point, we demonstrate the source-free principle of directed ELs that underlies the mechanism for EC formation. Our Letter not only enriches the diversity of non-Hermitian exceptional point configurations, but also highlights the new potential for non-Hermitian physics in second-order dynamical systems.

Robust topological superconductivity in spin–orbit coupled systems at higher-order van Hove filling

Van Hove singularities in proximity to the Fermi level promote electronic interactions and generate diverse competing instabilities. It is also known that a nontrivial Berry phase derived from spin–orbit coupling can introduce an intriguing decoration into the interactions and thus alter correlated phenomena. However, it is unclear how and what type of new physics can emerge in a system featured by the interplay between van Hove singularities (VHSs) and the Berry phase. Here, based on a general Rashba model on the square lattice, we comprehensively explore such an interplay and its significant influence on the competing electronic instabilities by performing a parquet renormalization group analysis. Despite the existence of a variety of comparable fluctuations in the particle–particle and particle-hole channels associated with higher-order VHSs, we find that the chiral p±ip pairings emerge as two stable fixed trajectories within the generic interaction parameter space, namely the system becomes a robust topological superconductor. The chiral pairings stem from the hopping interaction induced by the nontrivial Berry phase. The possible experimental realization and implications are discussed. Our work sheds new light on the correlated states in quantum materials with strong spin–orbit coupling (SOC) and offers fresh insights into the exploration of topological superconductivity.