Metallic Quantum Research Articles

Superconductor to metal quantum phase transition with magnetic field in Josephson coupled lead islands on Graphene

Abstract Superconductor-to-metal transition with magnetic field and gate-voltage is studied in a Josephson junction array comprising of randomly distributed lead islands on exfoliated single-layer graphene. The superconductivity onset temperature at low magnetic-fields is fitted to the Werthamer-Helfand-Hohenberg theory to model the temperature dependence of the upper critical field. The magnetoresistance in the intermediate temperature and field regime is described using thermally activated flux flow dictated by field dependent activation barrier. The barrier also depends on the gate voltage which dictates the inter-island Josephson coupling and disorder. The magnetoresistance near the upper critical field at low temperatures shows signatures of a gate dependent continuous quantum phase transition between superconductor and metal. The finite size scaling analysis shows that this transition belongs to the $(2+1)$D-XY universality class without disorder.

Comparative Assessment between Glowing Family Elements of Metal and Graphene Quantum Dots Based on their Properties: A Theoretical and Experimental Study

The quantum dots (QDs) have wide range of applications in the field of biology and energy due to exceptionally photo-physical properties and highly active larger surface area. Both metal quantum dots (MQDs) and graphene quantum dots (GQDs) have created a new platform for quantum chemistry not only theoretical point of view but also open various real applications. The photo-physical properties arise due to tunable band gap and active functional groups adhere to the surface. Both MQDs and GQDs have very good properties such as solubility in wide range of solvent, good stability in photo-physical and chemical environment, less poisoning in animal body, small size and tunable photoluminescence is favourable for cell dynamics and imaging, up-conversion and down conversion photoluminescence nature, good electrochemical activity. The functionalization of QDs with micro and macromolecules in all direction are possible as results we find different shape of QDs due to very small size of QDs just like few atoms. Some theoretical studies have been observed to evaluate the origin of these properties. This review focused on the comparative studies including advantage and disadvantage between GQDs and MQDs based on their properties and also give significant imminent to motivate more encouraging development. Moreover, this review study offers significant insights for enhancing the characteristics of quantum dots.

Cutting edge technology for wastewater treatment using smart nanomaterials: recent trends and futuristic advancements.

Water is a vital component of our existence. Many human activities, such as improper waste disposal from households, industries, hospitals, and synthetic processes, are major contributors to the contamination of water streams. It is the responsibility of every individual to safeguard water resources and reduce pollution. Among the various available wastewater treatment (WWT) methods, smart nanomaterials stand out for their effectiveness in pollutant removal through absorption and adsorption. This paper examines the application of valuable smart nanomaterials in treating wastewater. Various nanomaterials, including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), nanoadsorbents, nanometals, nanofilters, nanocatalysts, carbon nanotubes (CNTs), nanosilver, nanotitanium dioxide, magnetic nanoparticles, nanozero-valent metallic nanoparticles, nanocomposites, nanofibers, and quantum dots, are identified as promising candidates for WWT. These smart nanomaterials efficiently eliminate toxic substances, microplastics, nanoplastics, and polythene particulates from wastewater. Additionally, the paper discusses comparative studies on the purification efficiency of nanoscience technology versus conventional methods.

Performance of Low-Dimensional Solid Room-Temperature Photodetectors-Critical View.

In the last twenty years, nanofabrication progress has allowed for the emergence of a new photodetector family, generally called low-dimensional solids (LDSs), among which the most important are two-dimensional (2D) materials, perovskites, and nanowires/quantum dots. They operate in a wide wavelength range from ultraviolet to far-infrared. Current research indicates remarkable advances in increasing the performance of this new generation of photodetectors. The published performance at room temperature is even better than reported for typical photodetectors. Several articles demonstrate detectivity outperforming physical boundaries driven by background radiation and signal fluctuations. This study attempts to explain these peculiarities. In order to achieve this goal, we first clarify the fundamental differences in the photoelectric effects of the new generation of photodetectors compared to the standard designs dominating the commercial market. Photodetectors made of 2D transition metal dichalcogenides (TMDs), quantum dots, topological insulators, and perovskites are mainly considered. Their performance is compared with the fundamental limits estimated by the signal fluctuation limit (in the ultraviolet region) and the background radiation limit (in the infrared region). In the latter case, Law 19 dedicated to HgCdTe photodiodes is used as a standard reference benchmark. The causes for the performance overestimate of the different types of LDS detectors are also explained. Finally, an attempt is made to determine their place in the global market in the long term.

Disordered non-Fermi liquid fixed point for two-dimensional metals at Ising-nematic quantum critical points

Understanding the influence of quenched random potential is crucial for comprehending the exotic electronic transport of non-Fermi liquid metals near metallic quantum critical points. In this study, we identify a stable fixed point governing the quantum critical behavior of two-dimensional non-Fermi liquid metals in the presence of a random potential disorder. By performing renormalization group analysis on a dimensional-regularized field theory for Ising-nematic quantum critical points, we systematically investigate the interplay between random potential disorder for electrons and Yukawa-type interactions between electrons and bosonic order-parameter fluctuations in a perturbative epsilon expansion. At the one-loop order, the effective field theory lacks stable fixed points, instead exhibiting a runaway flow toward infinite disorder strength. However, at the two-loop order, the effective field theory converges to a stable fixed point characterized by finite disorder strength, termed the “disordered non-Fermi liquid (DNFL) fixed point”. Our investigation reveals that two-loop vertex corrections induced by Yukawa couplings are pivotal in the emergence of the DNFL fixed point, primarily through screening disorder scattering. Additionally, the DNFL fixed point is distinguished by a substantial anomalous scaling dimension of fermion fields, resulting in pseudogap-like behavior in the electron’s density of states. These findings shed light on the quantum critical behavior of disordered non-Fermi liquid metals, emphasizing the indispensable role of higher-order loop corrections in such comprehension.

Electrochemical Detection of Bisphenol a By Modified Gold Electrode with Ternary Quantum Dot Metal Organic Framework Composites

Modified gold electrode with Metal-organic framework (MOFs), ternary quantum dots (TQDs) and their composite (TQDs@MOFs) were as electrochemical sensor to determine bisphenol A (BPA). A comparative electrochemical study of the MOFs, QDs and QDs@MOFs reveals that the composite (QDs@MOFs) have the highest conductivity, largest effective surface area, lowest peak potential separation (∆Ep) and the highest oxidation peak current. Under optimal conditions and wide range of BPA concentrations, the ternary quantum dots metal organic frameworks were a better sensor for bisphenol A with 0.488 nM limit of detection and 1.473 nM. limit of quantitation in comparison to metal organic framework and quantum dots. The results show that QDs@MOFs responded remarkable to BPA and could be adapted a practical and efficient efficient sensor for the determination of BPA

WITHDRAWN: Recent advances on the metal oxides and nanocomposites based on quantum dots and metal oxides for supercapacitor applications: A mini-review

Considering the limited resources of fossil fuels and the environmental pollution caused by their use, the need for alternative technology has become a global challenge. As a candidate for replacing fossil fuels, batteries have limitations such as the lack of sodium and lithium sources. Supercapacitors are a suitable alternative technology due to the availability of electrode materials. In this study, our team reviewed the supercapacitor performance of metal oxides and nanocomposites based on metal oxides and quantum dots to overcome the limitations of metal oxide electrode materials. In this study, by investigating the supercapacitor performance of nanocomposites based on metal oxide and quantum dots in three categories of carbon quantum dot, graphene quantum dot, and polymer dot, the performance of each quantum dot in improving the supercapacitor behavior of metal oxides was discussed. The results confirmed that the synergistic effect of quantum dots and metal oxides is improving the supercapacitor performance of nanocomposites. Also, the functional groups on the surface of the quantum dots accelerate the rate of penetration of ions and the rate of ion transfer. The results of this study confirmed that polymer dots have better performance among quantum dots with polymer properties and quantum dots properties at the same time which provides research opportunities for researchers in the field of supercapacitors.

All-optical modulator with photonic topological insulator made of metallic quantum wells

Abstract All-optical modulators hold significant prospects for future information processing technologies for they are able to process optical signals without the electro-optical convertor which limits the achievable modulation bandwidth. However, owing to the hardly-controlled optical backscattering in the commonly-used device geometries and the weak optical nonlinearities of the conventional material systems, constructing an all-optical modulator with a large bandwidth and a deep modulation depth in an integration manner is still challenging. Here, we propose an approach to achieving an on-chip ultrafast all-optical modulator with ultra-high modulation efficiency and a small footprint by using photonic topological insulators (PTIs) made of metallic quantum wells (MQWs). Since PTIs have attracted significant attention because of their unidirectional propagating edge states, which mitigate optical backscattering caused by structural imperfections or defects. Meanwhile, MQWs have shown a large Kerr nonlinearity, facilitating the development of minimally sized nonlinear optical devices including all-optical modulators. The proposed photonic topological modulator shows a remarkable modulation depth of 15 dB with a substantial modulation bandwidth above THz in a tiny footprint of only 4 × 10 µm2, which manifests itself as one of the most compact optical modulators compared with the reported ones possessing a bandwidth above 100 GHz. Such a high-performance optical modulator could enable new functionalities in future optical communication and information processing systems.

Giant optical second- and third-order nonlinearities at a telecom wavelength.

A material platform that excels in both optical second- and third-order nonlinearities at a telecom wavelength is theoretically and experimentally demonstrated. In this TiN-based coupled metallic quantum well structure, electronic subbands are engineered to support doubly resonant inter-subband transitions for an exceptionally high second-order nonlinearity and provide single-photon transitions for a remarkable third-order nonlinearity within the 1400-1600 nm bandwidth. The second-order susceptibility χ(2) reaches 2840 pm/V at 1440 nm, while the Kerr coefficient n2 arrives at 2.8 × 10-10 cm2/W at 1460 nm. The achievement of simultaneous strong second- and third-order nonlinearities in one material at a telecom wavelength creates opportunities for multi-functional advanced applications in the field of nonlinear optics.

Analogous electronic states in graphene and planer metallic quantum dots

Graphene nanostructures offer wide range of applications due to their distinguished and tunable electronic properties. Recently, atomic and molecular graphene were modeled following simple free-electron scattering by periodic muffin tin potential leading to remarkable agreement with density functional theory. Here we extend the analogy of the π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document}-electronic structures and quantum effects between atomic graphene quantum dots (QDs) and homogeneous planer metallic counterparts of similar size and shape. Specifically, we show that at high binding energies, below the M¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{M}$$\\end{document}-point gap, graphene QDs enclose confined states and standing wave quasiparticle interference patterns analogous to those reported on coinage metal surfaces for nanoscale confining structures such as vacancy islands and quantum corrals. These confined and quantum corral-like states in graphene QDs can be resolved in tomography experiments using angle-resolved photoemission spectroscopy. Likewise, the shape of near-Fermi frontier orbitals in graphene quantum dots can be reproduced from electron confinement within homogeneous metal QDs of identical size and shape. Furthermore, confined states analogous to those found in metallic quantum stadiums can be realized in coupled QDs of graphene for reduced separation. The present study offer a simple fundamental understanding of graphene electronic structures and also open the way towards efficient modeling of novel graphene-based nanostructures.

Quasi-Homoepitaxial Growth of Highly Strained Alkali-Metal Ultrathin Films on Kagome Superconductors.

Applying lattice strain to thin films, a critical factor to tailor their properties such as stabilizing a structural phase unstable at ambient pressure, generally necessitates heteroepitaxial growth to control the lattice mismatch with substrate. Therefore, while homoepitaxy, the growth of thin film on a substrate made of the same material, is a useful method to fabricate high-quality thin films, its application to studying strain-induced structural phases is limited. Contrary to this general belief, here the quasi-homoepitaxial growth of Cs and Rb thin films is reported with substantial in-plane compressive strain. This is achieved by utilizing the alkali-metal layer existing in bulk crystal of kagome metals AV3Sb5 (A=Cs and Rb) as a structural template. The angle-resolved photoemission spectroscopy measurements reveal the formation of metallic quantum well states and notable thickness-dependent quasiparticle lifetime. Comparison with density functional theory calculations suggests that the obtained thin films crystalize in the face-centered cubic structure, which is typically stable only under high pressure in bulk crystals. These findings provide a useful approach for synthesizing highly strained thin films by quasi-homoepitaxy, and pave the way for investigating many-body interactions in Fermi liquids with tunable dimensionality.

61‐2: Invited Paper: Light Emitting Diodes Based on Metal Halide Perovskites and Beyond

Light emitting diodes (LEDs) have wide applications from fullcolor displays to solid‐state lighting. Numerous types of luminescent materials have been explored for LEDs, ranging from inorganic semiconductors to metal complexes and quantum dots. Despite the rapid pace of development, LEDs have not achieved their full potentials in terms of performance and cost efficiency. Identifying new eco‐friendly materials for LEDs is of great interest. Recently, metal halide perovskites and perovskite‐related hybrid materials have emerged as new generation luminescent materials with unique optoelectronic properties. Here, some of our recent development of LEDs based on metal halide perovskites and perovskite‐related materials will be discussed.

Amplification and excitation of surface plasmon polaritons via four-wave mixing process

We suggest a scheme for the excitation and amplification of surface plasmon polaritons (SPPs) along the interface between metal and semiconductor quantum well (SQW), employing a four-wave mixing (FWM) process. The SQW consists of four-level asymmetric double quantum wells that exhibit quantum interference effects, which leads to the coupler-free excitation of SPPs. In our proposed system, the inherent losses of SPPs are compensated by introducing gain through the FWM process, resulting in a significant enhancement in the propagation length and penetration depth of SPPs. We further analyze the effect of gain on the long-range and short-range SPPs and observe that the propagation distance and lifetime of both types of SPPs are increased.

Superluminal propagation of surface plasmon polaritons via hybrid chiral quantum dots system

We present a novel methodology for enhancing superluminal surface plasmon polaritons (SPPs) propagations within a hybrid nanostructure configuration consisting of gold (Au) metal and chiral quantum dots (CQDs) medium. The arrangement of CQDs and metal hybrid nanostructures enables the production of SPPs when exposed to incident light. The resonances of SPPs within a hybrid nanostructure are determined through analytical calculations using Maxwell’s equations under specified boundary conditions, while the dynamics of the CQDs system are calculated using the density matrix approach. It is demonstrated that the propagation of SPPs is significantly influenced by both right-circularly polarized (RCP) and left-circularly polarized (LCP) SPPs. Additionally, we investigate the enhancement of superluminal SPPs propagation by varying the electron tunneling strength and the intensity of the control field within the hybrid system. The characteristics of RCP and LCP SPPs have been investigated, indicating a large negative group index and advancement in time. The observation of a large negative group index and advancement in time provides strong evidence for enhanced superluminal SPPs propagation within the proposed hybrid nanostructure. The results have potential applications in the fields of optical information processing, temporal cloaking, quantum communication, and the advancement of computer chip speed.

Analytical Modelling and Performance Characterization of Hybrid SET-MOS

Gordon Moore's "Moore's Law" suggests chip functionality demand doubles every 1.5-2 years, with global semiconductor technology roadmap recommending sub-nanometer ranges for IC production in nano-electronics. The single electron transistor (SET) is a promising nano-scale device that can be co-integrated with CMOS technology to improve performance. The paper explores the tunnelling effect between nanoparticles in single electron transistors (SET), revealing coulomb blockade transactions and resistance increases with reduced bias. It focuses on single electron transistors and pre-terminal devices, discussing IV characteristics, coulomb diamond plots, and metallic quantum dots. This research also explores the hybrid SET-FET based model, focusing on developing a room temperature SET in CMOS comparable technology with a Field Effect Transistor (FET). Prediction models and exploratory studies guide the integration of SET-FET technology. SIMON is a comprehensive simulator designed for single-electron devices and circuits. The output current is not impacted by capacitances up to 1 pF, and FET size in the micron range are appropriate for SET signal amplification up to 4 µA. This research explores the modelling of SET-FET technology in highlighting its ability to mitigate drawbacks in low drive current when combined with a FET. It also explores device variability mitigation in nanoscale array configurations, finding that SET-FET significantly reduces variability in larger arrays, despite the impact of capacitance and resistance.

Colour-Passive radiative cooling in optoelectronics with Silver/Quantum dot decorated silica multifunctional hybrid structures

The integration of solar cells into the architectural design is hindered by challenges such as passive cooling and colouration appeal. The present study proposes an approach to overcome these obstacles by developing colourful solar cells that maintain optimal performance while addressing limitations related to heat accumulation from plasmon metal nanoparticles and quantum dots (QDs). To attain this, silver/silica microsphere composites combined with CdSe/ZnS core/shell QDs are fabricated with two distinct sizes of Ag nanoparticles embedded around SiO2 microspheres. Upon coating CIGS cells with this hybrid structure, a visually striking vivid green colouration is observed, while ensuring performance efficiency. Furthermore, the radiative cooling capability of these cells is evaluated through indoor and outdoor experiments. Significantly, a substantial temperature reduction of up to 3.2 °C in CIGS cells is achieved when the hybrid structures were applied to the cell's surface under high solar irradiance. The study represents a significant contribution to innovative strategies targeted at achieving passive cooling effect and enhancing aesthetic integration in building-integrated photovoltaics applications.

N-doped graphene quantum dot-decorated MOF-derived yolk-shell ZnO/NiO hybrids to boost lithium and sodium ion battery performance

Surface engineering at the nanoscale to obtain robust interface between metal oxides and quantum dots is essential for improving the performance and stability of battery materials. Herein, we designed and prepared novel N-doped graphene quantum dot-modified ZnO/NiO anode materials with a well-defined yolk-shell structure for lithium and sodium-ion batteries. NG QDs were assembled on the ZnO/NiO microspheres using three different coupling strategies: solvothermal, direct adsorption and annealing under N2 atmosphere. The presence of NG QDs deposited on the ZnO/NiO hybrids promoted enhanced electrical conductivity, lower charge-transfer resistance and provides more active sites. As a result, NG-ZnO/NiO_s anode obtained by solvothermal route exhibited high reversible delithiation capacity of 912 mAh/g at 18.6 mA g−1 and excellent cycling performance with the average delithiation capacity of 525 mAh/g at 372 mA g−1 over 400 cycles. Moreover, application of the NG-ZnO/NiO_s elecrode in Na-ion batteries revealed decent electrochemical behavior with capacity values reaching 235 mAh/g at 18.6 mA g−1. Importantly, surface properties, morphology and electrochemical behavior of obtained NG-ZnO/NiO hybrids were dependent on the combination route of NG QDs with ZnO/NiO microspheres indicating that quality of heterojunction between composite components has significant impact on the electrode performance.

Realization of large-area ultraflat chiral blue phosphorene

Blue phosphorene (BlueP), a theoretically proposed phosphorous allotrope with buckled honeycomb lattice, has attracted considerable interest due to its intriguing properties. Introducing chirality into BlueP can further enrich its physical and chemical properties, expanding its potential for applications. However, the synthesis of chiral BlueP remains elusive. Here, we demonstrate the growth of large-area BlueP films on Cu(111), with lateral size limited by the wafer dimensions. Importantly, we discovered that the BlueP is characterized by an ultraflat honeycomb lattice, rather than the prevailing buckled structure, and develops highly ordered spatial chirality plausibly resulting from the rotational stacking with the substrate and interface strain release, as further confirmed by the geometric phase analysis. Moreover, spectroscopic measurements reveal its intrinsic metallic nature and different characteristic quantum oscillations in the image-potential states, which can be exploited for a range of potential applications including polarization optics, spintronics, and chiral catalysis.

Single-mode, surface-emitting quantum cascade laser at 26 μ m

We present the simulation, design, fabrication, and characterization of planarized double metal quantum cascade lasers based on InGaAs/GaAsSb. Intended for astrophysical heterodyne measurements and having the cavity embedded in benzocyclobutene, the devices are equipped with thermal bridges on either side of the ridge, in order to improve the heat dissipation. The lasers are shown to vertically emit a single mode around 26 μm in pulsed operation, with peak powers of ≈ 30 μW and a current density threshold of Jth = 3.7 kA/cm2. Maximum operation temperature is around 170 K, with the maximum supported duty cycle being extended from the initial 15% to about 30% with the help of the improved thermal management technique.

DNA-functionalized metal or metal-containing nanoparticles for biological applications.

The conjugation of DNA molecules with metal or metal-containing nanoparticles (M/MC NPs) has resulted in a number of new hybrid materials, enabling a diverse range of novel biological applications in nanomaterial assembly, biosensor development, and drug/gene delivery. In such materials, the molecular recognition, gene therapeutic, and structure-directing functions of DNA molecules are coupled with M/MC NPs. In turn, the M/MC NPs have optical, catalytic, pore structure, or photodynamic/photothermal properties, which are beneficial for sensing, theranostic, and drug loading applications. This review focuses on the different DNA functionalization protocols available for M/MC NPs, including gold NPs, upconversion NPs, metal-organic frameworks, metal oxide NPs and quantum dots. The biological applications of DNA-functionalized M/MC NPs in the treatment or diagnosis of cancers are discussed in detail.