Passive parity-time symmetry breaking transitions, where long-lived eigenmodes emerge in a locally dissipative system, have been extensively studied in recent years. Conventional wisdom says that they occur at exceptional points. Here we report the observation of multiple transitions showing the emergence of slowly decaying eigenmodes in a dissipative, Floquet electronic system with synthetic components. Remarkably, in our system, the modes emerge without exceptional points. Our setup uses an electrical oscillator inductively coupled to a dissipative oscillator, where the time-periodic inductive coupling and resistive-heating losses are independently controlled. With a Floquet dissipation, slowly-decaying eigenmodes emerge at vanishingly small dissipation strength in the weak coupling limit. With a moderate Floquet coupling, multiple instances of their emergence and disappearance are observed. With an asymmetric dimer model, we show that these transitions, driven by avoided-levelcrossing in purely dissipative systems, are generically present in static and Floquet domains.
Noise is generally thought as detrimental for energy transport in coupled oscillator networks. However, it has been shown that for certain coherently evolving systems, the presence of noise can enhance, somehow unexpectedly, their transport efficiency; a phenomenon called environment-assisted quantum transport (ENAQT) or dephasing-assisted transport. Here, we report on the experimental observation of such effect in a network of coupled electrical oscillators. We demonstrate that by introducing stochastic fluctuations in one of the couplings of the network, a relative enhancement in the energy transport efficiency of 22.5 ± 3.6% can be observed.
By considering the structure of holococcoliths (calcite plates that cover holococcolithophores, a haploid phase of the coccolithophore life cycle) as a photonic structure, we apply a discrete dipolar approximation to study the light backscattering properties of these algae. We show that some holococcolith structures have the ability to scatter the ultraviolet (UV) radiation. This property may represent an advantage for holococcolithophores possessing it, by allowing them to live higher in the water column than other coccolithophores.
In this collaborative study, the variables that affect the morphology of nanotubular arrays of titanium oxide ͑grown by anodization of titanium substrate͒ were analyzed by a fractional factorial ͑Taguchi͒ statistical experimental design. The growth voltage and water content of the medium were found to have the maximal impact on nanotube length as shown by an analysis of variance. Nanotubular array growth was monitored by electrochemical impedance spectroscopy ͑EIS͒ and the results were corroborated by other measurement probes ͑scanning electron microscopy, transient current-time profiles, voltammetry͒ as needed. Taken as a whole, the EIS data presented above support the validity of the Bojinov equivalent circuit model especially at growth times past a few minutes. Trends in the values of the equivalent circuit elements obtained from fits to the EIS data as a function of the growth variables are rationalized within the framework of a model proposed by Schmuki and co-workers for the growth and self-assembly of titania nanotubes on Ti substrates in fluoride-containing media.In this collaborative study, the anodic growth of nanotubular arrays of titanium oxide ͑on titanium substrate͒ was studied by electrochemical impedance spectroscopy ͑ECIS͒ and the experimental and modeling results were corroborated by other measurement probes ͓scanning electron microscopy ͑SEM͒, growth current density-time ͑ j-t͒ profiles, current density-voltage ͑ j-V͒ curves͔ as needed. Tailoring the structure and morphology of semiconductor materials on a nanometer size scale has fundamental and practical importance. 1 Nanotubular semiconductor arrays ͑NTA͒ are particularly of interest because of their unusual electronic transport and mechanical strength characteristics. In this regard, titania ͑TiO 2 ͒ nanotubes and nanotubular arrays have been the subject of many recent studies; these have been reviewed. 2-4 Array growth and selfassembly is underpinned by a delicate and complex interplay of oxide film growth and its subsequent dissolution processes by fluoride species in the electrolyte. Adding to the complexity are details associated with the adsorption and transport of ionic species and mechanical ͑stress͒ effects from oxide growth on the native metal substrate. 5,6 In spite of the rapidly maturing database on TiO 2 NTAs, the temporal aspects of nanotubular growth and self-assembly and the effect of key variables that affect the NTA morphology are still not completely understood. 7,8 Electrochemical impedance spectroscopy ͑EIS͒ ͑Ref. 6 and 7͒ is a particularly effective approach for the monitoring of oxide growth and dissolution in anodic environments. A recognized advantage of this technique is that the dynamical behavior of a metal/oxide interface can be probed in situ at the cost of a very small ac perturbation so that the observed processes are themselves not significantly affected by the probe unlike in the case of large-amplitude signal perturbations. 9,10 Thus it is not surprising that many examples exist for the use of EIS to study...
Flight velocity measurement is an important aspect of insect research that can aid insect identification and facilitate studies and monitoring of insect movements. We propose a novel scheme for the 1-D flight velocity measurement of insects, based on a near-IR Scheimpflug lidar system. We implement this new technique and apply it to study insects at the Salter Research Farm, Robertson County, Texas. The resolution property perpendicular to the probing direction of the Scheimpflug lidar system is explored and reveals the capability of retrieving the velocity component normal to the probing direction of insects passing through the field of view of our system. We observe a shift in wingbeat frequency, which indicates the presence of new insect species during the multi-day measurement. The study on 1-D flight velocity reveals a net directional movement of insects, providing supportive evidence of the arrival of a new species.
We report on the experimental observation of an emerging negative resistance in a system of coupled linear electronic RLC harmonic oscillators under the influence of multiplicative noise with long correlation time. When two oscillators are coupled by a noisy inductor, an analysis in the Fourier space of the electrical variables unveils the presence of an effective negative resistance, which acts as an energy transport facilitator. This might constitute a simple explanation of the now fashionable problem of energy transport assisted by noise in classical systems. The experimental setup is based on the working principle of an analog computer and by itself constitutes a versatile platform for studying energy transport in noisy systems by means of coupled electrical oscillator systems.
The use of LiF as a thin interlayer between the electron transport layer and cathode has played a pivotal role in remarkable advances in perovskite LEDs (PeLEDs); however, the mechanism behind the effect of LiF remains to be fully understood. Here, we report a combined experimental and computational study, from which we ascribe the benefits of a LiF interlayer to the migration of dissociated Li into the cathode and dissociated F into the anode. Electronic device simulations reveal that the former improves electron injection by lowering the Schottky barrier height, while the latter reduces the barrier width. These reduce turn-on voltage and improve current density and charge balance in LEDs. We fabricate PeLEDs with and without the LiF interlayer and link these materials and electronic phenomena to the device light-current− voltage characteristics. X-ray photoelectron spectroscopy obtained in sputter profiling of PeLEDs corroborates the dissociation of LiF.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.