Quantum Interference Research Articles

Structural and magnetic properties of Ni cluster embedded (111)NiO layers grown on (0001)GaN films

(111) NiO epitaxial layers embedded with crystallographically oriented Ni-clusters are grown on c-GaN/Sapphire templates using the pulsed laser deposition technique. Structural and magnetic properties of the films are examined by a variety of techniques including high-resolution x-ray diffraction, precession-electron diffraction, and superconducting quantum interference device magnetometry. It has been found that Ni-clusters are formed in the NiO matrix only at sufficiently low oxygen pressures during the growth. The study further reveals that the orientation, shape, size, density, and magnetic properties of these clusters depend strongly on the growth temperature (TG). Although most of the Ni-clusters are found to be obtained crystallographically aligned with the NiO matrix with Ni(111) ∥NiO(111), clusters with other orientations also exist, especially in samples grown at lower temperatures. The average size and density of the clusters increase with TG. The proportion of the Ni(111) ∥ NiO(111)-oriented clusters also improves as TG is increased. All cluster embedded films show ferromagnetic behavior even at room temperature. Easy-axis is found to be oriented in the layer plane in samples grown at relatively lower temperatures. However, it turns perpendicular to the layer plane for samples grown at sufficiently high temperatures. This reversal of easy-axis has been attributed to the size dependent competition between the shape and magnetoelastic and the surface anisotropies of the clusters. This composite material thus has great potential to serve as a spin-injector and spin-storage medium in GaN-based spintronics of the future.

Competition between chiral anomaly and weak antilocalization in Cd3As2 nanoplates

Negative longitudinal magnetoresistivity (nLMR) induced by the chiral anomaly together with the weak antilocalization (WAL) due to the quantum interference can be regarded as remarkable magnetotransport signatures for three-dimension (3D) topological semimetals. Here, we report the observation of high-temperature competition between the chiral anomaly and WAL by magnetotransport measurements on high-quality Cd3As2 nanoplates under parallel electromagnetic fields. We find that, the WAL dominates the magnetotransport in the weak magnetic fields, which decreases gradually and ultimately vanishes at a critical temperature Tc. In contrast, the chiral anomaly is robust against temperature and can survive up to room temperature. This competition between the chiral anomaly and WAL can be understood in terms of Berry phase, accompanying with the low carrier density in Cd3As2 nanoplates. Our work would offer a better understanding of magnetotransport properties governed by Berry phase and the nature of electronic states in topological semimetals.

Energy enhancement through noise minimization using acoustic metamaterials in a wind farm

The determinantal noise pollution from wind turbines has constricted the acceptance of wind energy, posing health and environmental concerns. Existing solutions often compromise wind turbine efficiency or wind farm output, limiting the full utilization of wind energy. To address this challenge, we propose a novel method of effectively employing acoustic metamaterials (AMMs) inside a wind farm that leverages phase cancellation for noise suppression and energy enhancement. Through a combined phase retrieval, noise propagation model, and genetic algorithm, we determine the optimal layout and structural design of these AMMs inside a wind farm to minimize noise. We present two AMM designs, full-walled and segmented, and demonstrate their effectiveness for both single-turbine and multiple-turbine layout scenarios by achieving 91% (in Pa) and 10%–68% (in Pa) noise reduction, respectively, compared to reference layouts. Furthermore, we exhibit the AMM's impact in enhancing the energy throughput of wind farms by installing an additional wind turbine in a noise-restricted area of an existing AMM-equipped wind farm while maintaining a 70% (in Pa) reduction in noise levels. This approach paves the way for constructing wind farms near urban-suburban areas, complying with landscaping and visual government policies, and securing community acceptance towards sustainable power generation systems.

Effect of junction critical current disorder in superconducting quantum interference filter arrays

Effect of junction critical current disorder in superconducting quantum interference filter arrays

Effects of nuclear structure and quantum interference on diffractive vector meson production in ultraperipheral nuclear collisions

Effects of nuclear structure and quantum interference on diffractive vector meson production in ultraperipheral nuclear collisions

Impact of quantum interference in cascade radiation on the absorption profile

Impact of quantum interference in cascade radiation on the absorption profile

Regularly Tuning Quantum Interference in Single‐Molecule Junctions through Systematic Substitution of Side Groups with Varied Electron Effects†

Comprehensive SummaryInvestigating the quantum interference effect in single molecules is essential to comprehensively understand the underlying mechanism of single‐molecule charge transport. In this study, we employed the mother molecule m‐OPE and introduced a series of side groups with various electronic effects at the 2‐position of the central phenyl ring, creating four daughter m‐OPE derivatives. The single molecular conductivities of these molecule wires were measured using the scanning tunneling microscope breaking junction technique. Our findings demonstrate that the substitutions regularly modulate the destructive quantum interference occurring within the m‐OPE molecules. By combining optical and electrochemical investigations, along with density functional theory computations, we discover that the conductivity of the molecules corresponds to the electron‐donating/withdrawing ability of the substituents. Specifically, by adjusting the electron structures of the molecular backbone, we can systematically tailor the destructive quantum interference in the m‐OPE molecules.

Quantum interference in superposed lattices

Charge transport in solids at low temperature reveals a material's mesoscopic properties and structure. Under a magnetic field, Shubnikov-de Haas (SdH) oscillations inform complex quantum transport phenomena that are not limited by the ground state characteristics and have facilitated extensive explorations of quantum and topological interest in two- and three-dimensional materials. Here, in elemental metal Cr with two incommensurately superposed lattices of ions and a spin-density-wave ground state, we reveal that the phases of several low-frequency SdH oscillations in [Formula: see text] and [Formula: see text] are no longer identical but opposite. These relationships contrast with the SdH oscillations from normal cyclotron orbits that maintain identical phases between [Formula: see text] and [Formula: see text] . We trace the origin of the low-frequency SdH oscillations to quantum interference effects arising from the incommensurate orbits of Cr's superposed reciprocal lattices and explain the observed [Formula: see text]-phase shift by the reconnection of anisotropic joint open and closed orbits.

Exploring the Impact of the HOMO-LUMO Gap on Molecular Thermoelectric Properties: A Comparative Study of Conjugated Aromatic, Quinoidal, and Donor-Acceptor Core Systems.

Thermoelectric materials have garnered significant interest for their potential to efficiently convert waste heat into electrical energy at room temperature without moving parts or harmful emissions. This study investigated the impact of the HOMO-LUMO (H-L) gap on the thermoelectric properties of three distinct classes of organic compounds: conjugated aromatics (isoindigos (IIGs)), quinoidal molecules (benzodipyrrolidones (BDPs)), and donor-acceptor systems (bis(pyrrol-2-yl)squaraines (BPSs)). These compounds were chosen for their structural simplicity and linear π-conjugated conductance paths, which promote high electrical conductance and minimize complications from quantum interference. Single-molecule thermoelectric measurements revealed that despite their low H-L gaps, the Seebeck coefficients of these compounds remain low. The alignment of the frontier orbitals relative to the Fermi energy was found to play a crucial role in determining the Seebeck coefficients, as exemplified by the BDP compounds. Theoretical calculations support these findings and suggest that anchor group selection could further enhance the thermoelectric behavior of these types of molecules.

Three-Coordinate Nickel and Metal-Metal Interactions in a Heterometallic Iron-Sulfur Cluster.

Biological multielectron reactions often are performed by metalloenzymes with heterometallic sites, such as anaerobic carbon monoxide dehydrogenase (CODH), which has a nickel-iron-sulfide cubane with a possible three-coordinate nickel site. Here, we isolate the first synthetic iron-sulfur clusters having a nickel atom with only three donors, showing that this structural feature is feasible. These have a core with two tetrahedral irons, one octahedral tungsten, and a three-coordinate nickel connected by sulfide and thiolate bridges. Electron paramagnetic resonance (EPR), Mössbauer, and superconducting quantum interference device (SQUID) data are combined with density functional theory (DFT) computations to show how the electronic structure of the cluster arises from strong magnetic coupling between the Ni, Fe, and W sites. X-ray absorption spectroscopy, together with spectroscopically validated DFT analysis, suggests that the electronic structure can be described with a formal Ni1+ atom participating in a nonpolar Ni-W σ-bond. This metal-metal bond, which minimizes spin density at Ni1+, is conserved in two cluster oxidation states. Fe-W bonding is found in all clusters, in one case stabilizing a local non-Hund state at tungsten. Based on these results, we compare different M-M interactions and speculate that other heterometallic clusters, including metalloenzyme active sites, could likewise store redox equivalents and stabilize low-valent metal centers through metal-metal bonding.

An efficient quantum algorithm for ensemble classification using bagging

AbstractEnsemble methods aggregate predictions from multiple models, typically demonstrating improved accuracy and reduced variance compared to individual classifiers. However, they often come with significant memory usage and computational time requirements. A novel quantum algorithm that leverages quantum superposition, entanglement, and interference to construct an ensemble of classification models using bagging as an aggregation strategy is introduced. Through the generation of numerous quantum trajectories in superposition, the authors achieve B transformations of the training set with only operations, allowing an exponential enlargement of the ensemble size while linearly increasing the depth of the corresponding circuit. Moreover, when assessing the algorithm's overall cost, the authors demonstrate that the training of a single weak classifier contributes additively to the overall time complexity, as opposed to the multiplicative impact commonly observed in classical ensemble methods. To illustrate the efficacy of the authors’ approach, experiments on reduced real‐world datasets utilising the IBM qiskit environment to demonstrate the functionality and performance of the proposed algorithm are introduced.

Towards the generation of mechanical Kerr-cats: awakening the perturbative quantum Moyal corrections to classical motion

The quantum to classical transition is determined by the interplay of a trio of parameters: dissipation, nonlinearity, and macroscopicity. Why is nonlinearity needed to see quantum effects? And, is not an ordinary pendulum quite nonlinear already? In this manuscript, we discuss the parameter regime where the dynamics of a massive oscillator should be quantum mechanical in the presence of dissipation. We review the outstanding challenge of the dynamical generation of highly quantum mechanical cat states of a massive ‘pendulum’, known as Kerr-cats. We argue that state-of-the-art cold atom experiments may be in a position to reach such a nonlinear regime, which today singles out superconducting quantum circuits. A way to stabilize Schrödinger cat superpositions of a mechanical atomic oscillator via parametric squeezing and further protected by an unusual form of quantum interference is discussed. The encoding of a neutral atom Kerr-cat qubit is proposed.

Coherent electronic coupling in quantum dot solids induces cooperative enhancement of nonlinear optoelectronic responses.

Synchronized dynamics of quantum dot (QD) ensembles are essential for generating ultrafast and giant optical responses beyond those of individual QDs. Increasing the strength of the direct electronic coupling between QDs is a key strategy for the realization of cooperative quantum phenomena. Here, we observe a quantum cooperative effect on nonlinear photocurrents caused by the coherent electronic coupling in semiconductor QD solids. We measure quantum interference signals cooperatively generated in QD solids. We control the inter-QD distance with atomic precision using bidentate ligands that strongly link the QDs. The harmonic quantum interference signals are strongly enhanced when shortening the molecular length of the ligand. Furthermore, we clarify that the coherence length of multiexcitons extends to neighbouring QDs. This finding is direct evidence that multiexciton coherent tunnelling assists the ultrafast exciton delocalization. Cooperative enhancement in QD solids may find application in advanced quantum optoelectronics.

Multiple frequency steps in synthetic antiferromagnet based double spin josephson junctions using CoFeB and Fe3Sn

Superconducting quantum interference device (SQUID) which is made of two parallel Josephson junctions has applications in magnetometry. A similar spin-based device is proposed here where spin superfluid in ferromagnet (FM) mimics the superconducting state. Two materials CoFeB and Fe3Sn are used for spin superfluid-based SQUID like device where easy plane anisotropy in CoFeB can be engineered and Fe3Sn has inherent easy plane anisotropy. Frequency varies in spin based proposed devices. Frequency increases and again decreases with the increase in both applied magnetic field and applied spin current. The proposed device can be used as nano oscillator and detector. The frequency in the proposed device shows multiple frequency steps which can be used for neuromorphic applications.

Observation of Anomalous Planar Hall Effect Induced by One-Dimensional Weak Antilocalization.

The confinement of electrons in one-dimensional (1D) space highlights the prominence of the role of electron interactions or correlations, leading to a variety of fascinating physical phenomena. The quasi-1D electron states can exhibit a unique spin texture under spin-orbit interaction (SOI) and thus could generate a robust spin current by forbidden electron backscattering. Direct detection of such 1D spin or SOI information, however, is challenging due to complicated techniques. Here, we identify an anomalous planar Hall effect (APHE) in the magnetotransport of quasi-1D van der Waals (vdW) topological materials as exemplified by Bi4Br4, which arises from the quantum interference correction of 1D weak antilocalization (WAL) to the ordinary planar Hall effect and demonstrates a deviation from the usual sine and cosine curves. The occurrence of 1D WAL is correlated to the line-shape Fermi surface and persistent spin texture of (100) topological surface states of Bi4Br4, as revealed by both our angle-resolved photoemission spectroscopy and first-principles calculations. By generalizing the observation of APHE to other non-vdW bulk materials, this work provides a possible characteristic of magnetotransport for identifying the spin/SOI information and quantum interference behavior of 1D states in 3D topological material.

Large second-order Josephson effect in planar superconductor-semiconductor junctions

We investigate the current-phase relations of Al/InAs-quantum well planar Josephson junctions fabricated using nanowire shadowing technique. Based on several experiments, we conclude that the junctions exhibit an unusually large second-order Josephson harmonic, the \sin(2\varphi)sin(2φ) term. First, superconducting quantum interference devices (dc-SQUIDs) show half-periodic oscillations, tunable by gate voltages as well as magnetic flux. Second, Josephson junction devices exhibit kinks near half-flux quantum in supercurrent diffraction patterns. Third, half-integer Shapiro steps are present in the junctions. Similar phenomena are observed in Sn/InAs quantum well devices. We perform data fitting to a numerical model with a two-component current phase relation. Analysis including a loop inductance suggests that the sign of the second harmonic term is negative. The microscopic origins of the observed effect remain to be understood. We consider alternative explanations which can account for some but not all of the evidence.

Charge-4e supercurrent in a two-dimensional InAs-Al superconductor-semiconductor heterostructure

AbstractSuperconducting qubits with intrinsic noise protection offer a promising approach to improve the coherence of quantum information. Crucial to such protected qubits is the encoding of the logical quantum states into wavefunctions with disjoint support. Such encoding can be achieved by a Josephson element with an unusual charge-4e supercurrent emerging from the coherent transfer of pairs of Cooper-pairs. In this work, we demonstrate the controlled conversion of a conventional charge-2e dominated to a charge-4e dominated supercurrent in a superconducting quantum interference device (SQUID) consisting of gate-tunable planar Josephson junctions. We investigate the ac Josephson effect of the SQUID and measure a dominant photon emission at twice the fundamental Josephson frequency together with a doubling of the number of Shapiro steps, both consistent with the appearance of charge-4e supercurrent. Our results present a step towards protected superconducting qubits based on superconductor-semiconductor hybrid materials.

On the coupling of magnetic moments to superconducting quantum interference devices

We investigate the coupling factor φ µ that quantifies the magnetic flux Φ per magnetic moment µ of a point-like magnetic dipole that couples to a superconducting quantum interference device (SQUID). Representing the dipole by a tiny current-carrying (Amperian) loop, the reciprocity of mutual inductances of SQUID and Amperian loop provides an elegant way of calculating ϕμ(r,eˆμ) vs. position r and orientation eˆμ of the dipole anywhere in space from the magnetic field BJ(r) produced by a supercurrent circulating in the SQUID loop. We use numerical simulations based on London and Ginzburg–Landau theory to calculate φ µ from the supercurrent density distributions in various superconducting loop geometries. We treat the far-field regime ( r≳a= inner size of the SQUID loop) with the dipole placed on (oriented along) the symmetry axis of circular or square shaped loops. We compare expressions for φ µ from simple filamentary loop models with simulation results for loops with finite width w (outer size A > a), thickness d and London penetration depth λ L and show that for thin ( d≪a ) and narrow (w < a) loops the introduction of an effective loop size aeff in the filamentary loop-model expressions results in good agreement with simulations. For a dipole placed right in the center of the loop, simulations provide an expression ϕμ(a,A,d,λL) that covers a wide parameter range. In the near-field regime (dipole centered at small distance z above one SQUID arm) only coupling to a single strip representing the SQUID arm has to be considered. For this case, we compare simulations with an analytical expression derived for a homogeneous current density distribution, which yields excellent agreement for λL>w,d . Moreover, we analyze the improvement of φ µ provided by the introduction of a narrow constriction in the SQUID arm below the magnetic dipole.

Removal of Fe3+ Ions from Aqueous Solutions by Adsorption on Natural Eco-Friendly Brazilian Palygorskites

This work focuses on the characterization of five palygorskite clays from the Brazilian state of Piaui and their feasibility as eco-friendly adsorbents for the removal of Fe3+ ions from aqueous solutions. For characterization, we applied the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), size distribution measurements, density measurement by He pycnometry, superconducting quantum interference device (SQUID) magnetometry, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTA), zeta potential measurement, hydrophobicity determination by contact angle, Brunauer–Emmett–Teller surface area analysis (BET technique) and atomic force microscopy (AFM). Batch experiments were performed in function of process parameters such as contact time and initial concentration of Fe3+. The natural palygorskites (Palys) had excellent performance for the removal of Fe3+ from aqueous solutions by adsorption (around 60 mg/g), and the Langmuir is supposedly the best model fitted the experimental data.

Resonance and Anti-resonance in transport through quantum dots-Majorana bound states hybrid structure

We calculate the linear conductance through a double quantum-dot system with a normal metal lead, which is enclosed in a closed shape where quantum dot-1 is connected to Majorana bound states (MBSs). The Quantum dots configuration from parallel to series allows for a transition in the shape of resonant to non-resonant in the spectrum. This is caused by quantum interference between the energy levels. This process results in the formation of bonding and antibonding states that are involved in electron transport. An asymmetric quantum dots configuration can produce a Fano resonance, and its position can be adjusted by altering the energy levels.