Diode Effect Research Articles

Nonequilibrium thermal rectification at the junction of harmonic chains.

A thermal diode or rectifier is a system that transmits heat or energy in one direction better than in the opposite direction. We investigate the influence of the distribution of energy among wave numbers on the diode effect for the junction of two dissimilar harmonic chains. An analytical expression for the diode coefficient, characterizing the difference between heat fluxes through the junction in two directions, is derived. It is shown that the diode coefficient depends on the distribution of energy among wave numbers. For an equilibrium energy distribution, the diode effect is absent, while for non-equilibrium energy distributions the diode effect is observed even though the system is harmonic. We show that the diode effect can be maximized by varying the energy distribution and relative position of spectra of the two harmonic chains. Conditions are formulated under which the system acts as an ideal thermal rectifier, i.e., transmits heat only in one direction. The results obtained are important for understanding the heat transfer in heterogeneous low-dimensional nanomaterials.

Sign reversal diode effect in superconducting Dayem nanobridges

Supercurrent diodes are nonreciprocal electronic elements whose switching current depends on their flow direction. Recently, a variety of composite systems combining different materials and engineered asymmetric superconducting devices have been proposed. Yet, ease of fabrication and tunable sign of supercurrent rectification joined to large efficiency have not been assessed in a single platform so far. We demonstrate that all-metallic superconducting Dayem nanobridges naturally exhibit nonreciprocal supercurrents under an external magnetic field, with a rectification efficiency up to ~ 27%. Our niobium nanostructures are tailored so that the diode polarity can be tuned by varying the amplitude of an out-of-plane magnetic field or the temperature in a regime without magnetic screening. We show that sign reversal of the diode effect may arise from the high-harmonic content of the current phase relation in combination with vortex phase windings present in the bridge or an anomalous phase shift compatible with anisotropic spin-orbit interactions.

Josephson transistor from the superconducting diode effect in domain wall and skyrmion magnetic racetracks

Josephson transistor from the superconducting diode effect in domain wall and skyrmion magnetic racetracks

The implication of blue light-emitting diode on mesenchymal stem cells: a systematic review.

The application of blue light (400-480nm) in photobiotherapy remains controversial. This systematic review aimed to collect and analyze the biological effects of blue light-emitting diode (LED) on mesenchymal stem cells (MSCs). Inclusion and exclusion criteria were formulated, and relevant English articles from January 1982 to September 2022 were searched in PubMed, Scopus, and Web of Science. Nine articles with a medium (n = 4) to low (n = 5) risk of bias were included. Most of the MSCs reported were derived from human tissue; only one article used MSCs derived from mouse. The wavelength of the LED used was in the 400-480nm range, and the irradiation modes were continuous (n = 8) and pulse waves (n = 1). A chiral polarizer was used in one such study in which the irradiance was 14 mW/cm2 and the irradiation time was 24h. The energy densities used in other studies were between 0.378 and 72J/cm2, and the irradiation times were between 10 and 3600s. Blue LED light can inhibit proliferation and promote differentiation of MSCs in an appropriate energy density range, which may be related to the activation of transient receptor potential vanilloid 1 (TRPV1). Additionally, polarized light may reduce the toxic effects of blue light on MSCs. However, the heterogeneity of the design schemes and LED parameters, as well as the small number of studies, limited the conclusiveness of the review. Therefore, further studies are needed to determine the optimal irradiation strategy for promoting MSC function.

The effects of diode and Er:YAG laser applications on the surface topography of titanium grade 4 and titanium zirconium discs with sand-blasted and acid-etched (SLA) surfaces

BackgroundLaser application for the treatment of peri‑implantitis provides a variety of advantages; however, depending on the laser type and parameters, it may also have adverse effects on the implant surface qualities. This study's objective is to assess the effects of laser type and parameters on the surface properties of two different titanium-based implant materials: titanium Grade 4 (Ti-Grade 4) and titanium zirconium (Ti-Zr) discs with sand-blasted and acid-etched (SLA) surfaces under in vitro conditions. Material & methodSand-blasted and acid-etched discs made of titanium grade 4 (Ti-Grade 4) and titanium zirconium (Ti-Zr) were treated using 808 nm AlGaAs (diode) and 2940 nm Er:YAG lasers with varying parameters (i.e., diode laser in continuous wave mode, Er:YAG in short pulse mode, and Er:YAG in variable square pulse mode with four different doses). Then, the surface morphology and topography of the treated discs were characterized using scanning electron microscopy and optical profilometry. ResultsThe 3D surface topographies of discs treated with a high power Er:YAG laser displayed irregular peaks and deep valleys, indicating surface deterioration. The average surface roughness values (Sa) of both discs varied with laser type and parameters (3.55–4.80 µm for Ti-Grade 4 versus 3.25–4.5 µm for Ti-Zr). With diode laser applications, the topography features of the discs were preserved despite a small number of irregular valleys and peaks. However, the surface morphologies of the discs were dramatically altered by erosion and local melting because of the Er:YAG laser treatment. ConclusionDiode laser application appears to be the most reliable method for treating peri‑implantitis, as diode laser-treated implants retained their overall surface quality despite a small number of irregular peaks and valleys.

Neutron radiation induced effects in 4H-SiC PiN diodes

Silicon carbide (SiC) is a wide band gap semiconductor and an attractive candidate for applications in harsh environments such as space, fusion, or future high luminosity colliders. Due to the large band gap, the leakage currents in SiC devices are extremely small, even after irradiation to very high fluences, enabling operation without cooling and at high temperatures. This study investigates the effect of neutron irradiation on 50 μm p-n 4H-SiC diodes using current-voltage, capacitance-voltage, and charge collection efficiency (CCE) measurements up to neutron fluences of 1 × 1016 n eq/cm2. The leakage currents of the investigated devices remained extremely small, below 10 pA at 1.1 kV reverse bias. In the forward bias, a remarkable drop of the current was observed, which was attributed to an increased epi resistivity due to compensation of the epi layer doping by deep-level defects. The CCE was evaluated for alpha particles from a radioactive source, a 62.4 MeV proton beam at the MedAustron ion therapy center and using UV-TCT. The charge collection efficiency in reverse bias was shown to scale directly with the 1 MeV equivalent fluence Φeq as CCE∝Φeq -0.63±0.01. A CCE better than 50% was able to be obtained for fluences up to 1 × 1015 n eq/cm2. Because of the low currents in the forward direction, particle detection was also possible in forward bias, where the CCE was found to be increased relative to reverse bias. Furthermore, a significant dependency on the amount of injected charge was observed, with the CCE surpassing 100% in alpha and UV-TCT measurements, requiring further systematic investigation.

Pre-harvest supplemental LED treatments led to improved postharvest quality of sweet basil leaves.

This study determined the effects of supplemental light-emitting diode (LED) treatments on the nutrient quality and volatile compounds of sweet basil leaves during stimulated shelf-life. Basil plants were grown in a greenhouse under different supplemental LEDs (white, blue, red, or red + blue each at 100μmolm-2s-1), while plants grown under sunlight served as the control. The findings revealed that plant height and canopy of basil showed a significant increase under red LED irradiation, while the leaf area was improved by the blue LED exposure. Moreover, blue LEDs enhanced the levels of phenolic compounds, total phenolic contents, total flavonoid contents, and PAL (phenylalanine ammonia-lyase) activity in harvested sweet basil leaves. Additionally, red + blue LEDs lighting stimulated the production of volatile compounds. During storage, the samples treated with blue LEDs maintained a higher quality compared to the control samples. In conclusion, the application of blue or red + blue LEDs prior to harvest can be beneficial for promoting and preserving the nutritional quality of sweet basil.

Nonreciprocal Transport and Optical Phenomena in Quantum Materials

In noncentrosymmetric materials, the responses (for example, electrical and optical) generally depend on the direction of the external stimuli, called nonreciprocal phenomena. In quantum materials, these nonreciprocal responses are governed by the quantum geometric properties and symmetries of the electronic states. In particular, spatial inversion ([Formula: see text]) and time-reversal ([Formula: see text]) symmetries play crucial roles, which are also relevant to the geometric Berry phase. Here, we give a comprehensive review of the nonreciprocal transport and optical responses including ( a) the magnetochiral anisotropy, i.e., the nonlinear resistivity with respect to the electric field, in semiconductors and metals, ( b) the nonreciprocal transport in superconductors such as the nonreciprocal paraconductivity and the superconducting diode effect in bulk and Josephson junctions, and ( c) the second-order nonlinear optical effects in the electric field of light, including the geometric shift current in nonmagnetic systems, magnetic systems, and superconductors.

Reversible charge injection-controlled resistance switching in BiFeO3 ferrodiodes

The ferroelectric diode effect is a promising candidate for resistive memory applications, but the precise role of defects in the current switching mechanism remains unclear. Here, we investigated ferroelectric SrRuO3/BiFeO3/SrRuO3 capacitors and observed strong diode current. The capacitors exhibited preferred polarization orientation toward the bottom electrode in the presence of an imprint field, as evidenced by poor polarization retention of upward polarizations at a bias voltage of 1 V. Interfacial defect-mediated charge injection and trapping enabled by negative voltage poling reduced the built-in field and improved the retention property at the expense of reduced diode current. This phenomenon can be reversed by long-time positive voltage poling, allowing the deeply trapped charges to be expelled out of the trap for the rejuvenation of the diode current. Our study provides experimental evidence that interfacial defects modify the diode current in a manner opposite to that of the switched polarization.

Effects of various light-emitting diode wavelengths on periodontopathic bacteria and gingival fibroblasts: An in vitro study

BackgroundIn recent years, light has been used for bacterial control of periodontal diseases. This in vitro study evaluated the effects of light-emitting diode (LED) irradiation at different wavelengths on both Porphyromonas gingivalis and human gingival fibroblasts (HGF-1). MethodsP. gingivalis suspension was irradiated with LEDs of 365, 405, 450, 470, 565, and 625 nm at 50, 100, 150, and 200 mW/cm2 for 3 min (radiant exposure: 9, 18, 27, 36 J/cm2, respectively). Treated samples were anaerobically cultured on agar plates, and the number of colony-forming units (CFUs) was determined. Reactive oxygen species (ROS) levels were measured after LED irradiation. The viability and damage of HGF-1 were measured through WST-8 and lactate dehydrogenase assays, respectively. Gene expression in P. gingivalis was evaluated through quantitative polymerase chain reaction. ResultsThe greatest reduction in P. gingivalis CFUs was observed on irradiation at 365 nm with 150 mW/cm2 for 3 min (27 J/cm2), followed by 450 and 470 nm under the same conditions. While 365-nm irradiation significantly decreased the viability of HGF-1 cells, the cytotoxic effects of 450- and 470-nm irradiation were comparatively low and not significant. Further, 450-nm irradiation indicated increased ROS production and downregulated the genes related to gingipain and fimbriae. The 565- and 625-nm wavelength groups exhibited no antibacterial effects; rather, they significantly activated HGF-1 proliferation. ConclusionsThe 450- and 470-nm blue LEDs showed high antibacterial activity with low cytotoxicity to host cells, suggesting promising bacterial control in periodontal therapy. Additionally, blue LEDs may attenuate the pathogenesis of P. gingivalis.

Emergent ferromagnetism with superconductivity in Fe(Te,Se) van der Waals Josephson junctions

Ferromagnetism and superconductivity are two key ingredients for topological superconductors, which can serve as building blocks of fault-tolerant quantum computers. Adversely, ferromagnetism and superconductivity are typically also two hostile orderings competing to align spins in different configurations, and thus making the material design and experimental implementation extremely challenging. A single material platform with concurrent ferromagnetism and superconductivity is actively pursued. In this paper, we fabricate van der Waals Josephson junctions made with iron-based superconductor Fe(Te,Se), and report the global device-level transport signatures of interfacial ferromagnetism emerging with superconducting states for the first time. Magnetic hysteresis in the junction resistance is observed only below the superconducting critical temperature, suggesting an inherent correlation between ferromagnetic and superconducting order parameters. The 0-π phase mixing in the Fraunhofer patterns pinpoints the ferromagnetism on the junction interface. More importantly, a stochastic field-free superconducting diode effect was observed in Josephson junction devices, with a significant diode efficiency up to 10%, which unambiguously confirms the spontaneous time-reversal symmetry breaking. Our work demonstrates a new way to search for topological superconductivity in iron-based superconductors for future high Tc fault-tolerant qubit implementations from a device perspective.

Controllable ion transport in bilayer graphene with charged nanopores

Heterogeneous membrane structures exhibiting ion diode effects have attracted significant interest in energy conversion and storage. Herein, asymmetric double-layer graphene stacks with charged nanopores are constructed and placed in a KCl solution to study the controllable ion transport properties. Ion current rectification (ICR) is observed and the switching ratio is up to 102 by leveraging the asymmetric structure, charge, and interlayer distance. The trapping behavior of cations (K+) and anions (Cl−) in the nanochannels is investigated by applying bias voltages, and peak ion capture occurs at an electric field of E = 0.02 V/Å. The underlying mechanism of ICR is elucidated according to the dependence between the ion current and carrier concentration in the nanopores. The results provide valuable insights into the ICR mechanism and reveal high potential in the energy field.

Spontaneous superconducting diode effect in non-magnetic Nb/Ru/Sr2RuO4 topological junctions

Non-reciprocal electronic transport in a material occurs if both time reversal and inversion symmetries are broken. The superconducting diode effect (SDE) is an exotic manifestation of this type of behavior where the critical current for positive and negative currents are mismatched, as recently observed in some non-centrosymmetric superconductors with a magnetic field. Here, we demonstrate a SDE in non-magnetic Nb/Ru/Sr2RuO4 Josephson junctions without applying an external magnetic field. The cooling history dependence of the SDE suggests that time-reversal symmetry is intrinsically broken by the superconducting phase of Sr2RuO4. Applied magnetic fields modify the SDE dynamically by randomly changing the sign of the non-reciprocity. We propose a model for such a topological junction with a conventional superconductor surrounded by a chiral superconductor with broken time reversal symmetry.

Nonlocal magnon transconductance in extended magnetic insulating films. I. Spin diode effect

Nonlocal magnon transconductance in extended magnetic insulating films. I. Spin diode effect

Engineered Heterogenous Subnanochannel Membranes with a Tri‐Continuous Pore Structure of Large Geometry Gradient for Massively Enhanced Osmotic Power Conversion from Organic Solutions

AbstractHeterogenous nanofluidic membranes with bi‐layer structures and ionic diode effect are shown great potential in efficiently harvesting the energy existing in a salinity gradient (or called the osmotic power conversion). However, exploitation of a heterogenous membrane with superior ion selectivity, excellent conductance, and strong ionic diode characteristics has remained a great challenge. Here, a novel heterogenous subnanochannel membrane with a tri‐continuous pore structure of a large geometry gradient ranging from sub‐nanoscale to nanoscale to sub‐microscale, which is composed of a thin and crack‐free layer of zeolitic imidazolate framework‐8 (ZIF‐8)/polystyrene sulfonate (PSS) membranes and an aligned branch‐type alumina nanochannel membrane (BANM) is reported. It is demonstrated that such a tri‐continuous pore structure can endow the exploited membrane, ZIF‐8/PSS@BANM, with enhanced ion selectivity, strong ion current rectification, and ultrafast ion transport properties, in organic electrolyte solutions. Thus, an amazingly high power of ≈50.5 W m−2 is produced by mixing a 2 m LiCl‐methanol and pure methanol solutions, which is over 45‐fold higher than the existing membranes. Realizing high ion selectivity and amplified directional ion transport at sub‐nanoconfined spaces in organic solvents paves the new way to develop ion‐channel‐mimetic membranes toward efficient ion separation and high‐performance energy harvesters for battery applications.

Diode type unidirectional conduction in Hall measurement of magnetic honeycomb lattice

Artificial magnetic honeycomb lattice is emerging as a new platform for spintronics research applications, as evidenced from recent findings of magnetic diode effect and collective magnetic switching phenomena in different lattice geometries. In this report, we present Hall measurements on thermally tunable artificial magnetic honeycomb lattice. Experimental investigation using detailed Hall probe measurements reveals diode-type unidirectional conduction in both longitudinal and Hall resistances. The unidirectional conduction persists to low temperature but remains unaffected to modest application of perpendicular magnetic field. The behavior can be understood in terms of topological magnetic charges that arise on the vertices of honeycomb lattice and affect electrical transport properties. The experimental finding can be utilized for the design of spintronic logic devices.

Characteristics of LED light-induced geometrical isomerization and degradation of astaxanthin and improvement of the color value and crystallinity of astaxanthin utilizing the photoisomerization

The effects of light-emitting diode (LED) irradiation characterized by different emission wavelengths on the E/Z-isomerization and degradation of astaxanthin were investigated. LED irradiation slightly promoted Z-isomerization of astaxanthin, whereas the all-E-isomerization was highly efficiently promoted at specific wavelengths, especially at 365 nm. Astaxanthin isomers did not degrade significantly when dissolved in ethanol and subjected to LED irradiation conditions for 300 min. However, significant degradation was achieved when ethyl acetate was used for dissolution, and the samples were irradiated at the wavelength of 405 nm. The addition of α-tocopherol suppressed the photodegradation of astaxanthin. LED irradiation significantly affected the physical properties of astaxanthin Z-isomers. Irradiation with 365, 405, and 470 nm LEDs enhanced the color value (redness) and crystallinity of the Z-isomers via an all-E-isomerization reaction. These findings can contribute to the development of technologies that can arbitrarily control the E/Z-isomer ratio and physical properties of astaxanthin.

Blue Light-Emitting Diode Irradiation Without a Photosensitizer Alters Oral Microbiome Composition of Ligature-Induced Periodontitis in Mice.

Objective: This study investigated the suppressive effects of blue light-emitting diode (LED) irradiation on bone resorption and changes in the oral microbiome of mice with ligature-induced periodontitis. Background: Wavelength of blue light has antimicrobial effects; however, whether blue LED irradiation alone inhibits the progression of periodontitis remains unclear. Methods: Nine-week-old male mice ligated ligature around the right maxillary second molar was divided into ligation alone (Li) and ligation with blue LED irradiation (LiBL) groups. The LiBL group underwent blue LED (wavelength, 455 nm) irradiation four times in a week at 150 mW/cm2 without a photosensitizer on the gingival tissue around the ligated tooth at a distance of 5 mm for 5 min. The total energy density per day was 45 J/cm2. Bone resorption was evaluated using micro-computed tomography at 8 days. Differences in the oral microbiome composition of the collected ligatures between the Li and LiBL groups were analyzed using next-generation sequencing based on the 16S rRNA gene from the ligatures. Results: Blue LED irradiation did not suppress bone resorption caused by ligature-induced periodontitis. However, in the LiBL group, the α-diversity, number of observed features, and Chao1 were significantly decreased. The relative abundances in phylum Myxococcota and Bacteroidota were underrepresented, and the genera Staphylococcus, Lactococcus, and Lactobacillus were significantly overrepresented by blue LED exposure. Metagenomic function prediction indicated an increase in the downregulated pathways related to microbial energy metabolism after irradiation. The co-occurrence network was altered to a simpler structure in the LiBL group, and the number of core genera decreased. Conclusions: Blue LED irradiation altered the composition and network of the oral microbiome of ligature-induced periodontitis in mice.

Blue and UV light-emitting diodes (LEDs) disturb the greenhouse whitefly (Trialeurodes vaporariorum) from its host

Push–pull strategy is a well-known and widely used technique for integrated pest management, leading to the reduction of insecticides. This strategy involves the use of mostly visual and chemical stimuli to repel pests from a valuable crop (push) and attract them to an appealing target, e.g., a trap, (pull). Based on former results, this study explored the effect of light-emitting diodes (LEDs) as repelling factors of whiteflies (push). Wavelengths of blue and ultraviolet (UV) were investigated in different light intensities and exposure times in no-choice experiments, under controlled conditions. Whiteflies were exposed directly to LEDs on the underside of tomato leaves and number of repelled insects was counted. The results showed that light intensity and insect repellency were positively related. Insect repellency increased up to tenfold with longer light exposure period. Wavelength of blue and combination of blue + UV repelled more than 87% of whiteflies in light conditions. In darkness, results were only slightly different. The results reveal the property of blue light to repel whiteflies from its host and that addition of UV to blue enhances this effect. They further demonstrate that whitefly vision is dependent on wavelength, light intensity and exposure period. The contribution of the results on understanding the visual behavior of whiteflies and their possible implementation on pest control strategies is discussed.

Electrostatic Damage Influenced by Bottom Gate-Like Effects in Flexible Organic Light-Emitting Diodes

Electrostatic Damage Influenced by Bottom Gate-Like Effects in Flexible Organic Light-Emitting Diodes