Hopping Behavior Research Articles

Coupling of magnetism and transport properties to the lattice degrees of freedom inNdBaCo2O5+δ (δ ∼ 0.65).

We have studied the origin of zero volume expansion below the Curie temperature (Tc), variable range hopping (VRH) behaviour using structural, magnetic, transport and thermal studies on the oxygen deficient double perovskite NdBaCo2O5+del (del= 0.65). The valence state of Co ions and the possible properties exhibited by such compound were studied using electronic structure calculations for del= 0.75. Careful investigation of structure shows that the compound stabilizes in tetragonal structure (P4/mmm) having 2apx2apx2ap (222) superstructure, where ap is the cubic perovskite lattice parameter. The compound exhibits a minimum in resistivity, ferromagnetic (FM) and ferrimagnetic (FeM) transitions around 375 K, 120 K (Tc) and 60 K, respectively with signature of Griffiths phase above Tc. Our detailed structural analysis suggests signature of the onset of the above magnetic transitions at temperatures well above its stabilisation at long range level thereby leading to VRH behaviour. The observed zero thermal expansion in volume below Tc appears to be due to competing magnetic interactions within and between the magnetic sublattices. Our electronic structure calculations in FM and FeM configurations show (a) Co ions stabilize in intermediate spin (IS) state, having oxidation state less than +3 (b) half metallicity, (c) the behaviour of the density of states is in line with the resistivity results, and (d) unusually high orbital angular moment in Co ions with inclusion of spin orbit coupling (soc). Our results show the possibility of coupling between magnetism and ferroelectricity. We believe that our results especially on the valence state of the Co ion, zero thermal expansion in volume, short range magnetic orderings and the connection between different degrees of freedom will be helpful in clearing the ambiguities existing in literature on the nature of magnetism and thereby aiding in designing new functionalities by maneuvering the strength of soc.

Gate-driven transition temperatures of electron hopping behaviors in Hubbard bands formed by dopant-induced QD array in silicon nanowire

Abstract Dopant atoms confined in silicon nanoscale channel can be ionized to form quantum dots (QDs). Several dopant atoms couple with each other forming energy bands, where the electron hopping behavior can be described by the Hubbard model. This characteristic renders dopant-induced QDs particularly appealing for applications in nanoelectronic and quantum devices. Herein we study the gate-driven transition temperatures of electron hopping behavior in the upper Hubbard bands (UHBs) and lower Hubbard bands (LHBs) formed by dopant-induced QD array in junctionless silicon nanowire transistors. The gate-dependent transition temperatures are calculated for three stages of electron hopping behaviors including Efros–Shklovskii Variable Range Hopping (ES-VRH), Mott VRH and Nearest Neighbor Hopping (NNH). Our experimental results indicate that the ES-VRH in arrays of dopant atoms occurs in the domination of a long-range Coulomb interaction, in which the hopping distance relies on the Coulomb gap. Furthermore, the localization length of ES-VRH can be modulated by gate voltages. Those factors lead to the significant difference of transition temperatures between the UHBs and LHBs. In addition, we find that the source–drain bias voltage can effectively modulate the transition temperatures between VRH and NNH by thermal activation energies under different bias voltages Vds.

Job Hopping Behavior in the Upstream Sector of Oil and Gas Industry in Malaysia

Purpose: The research aims to identify what contributes to the job-hopping behavior to the mentioned industry within Malaysia’s workforce. Theoretical reference: The study employs Social Exchange Theory (SET) to investigate job-hopping behavior in Malaysia's upstream oil and gas sector. It explores the impact of remuneration packages, career advancement opportunities, and learning development on employees' intentions to change jobs. SET helps understand how self-interest and cost-benefit analyses influence this behavior. Method: The study took a quantitative and cross-sectional approach, whereby the research tools were derived from numerous previous studies. Primary knowledge on job-hopping behavior was obtained based on input collected from research surveys. The data allows us to establish the relationship between job hopping behavior and the independent variables identified. Results and Conclusion: The investigation of this study discovered that the three hypotheses offered have a significant relationship of the job-hopping behaviors with remuneration package, career advancement and leaning development. Implications of research: This study provides insight for employers and academic researchers in understanding correlation of each determinant that leads to employees’ job-hopping behavior, which could also benefit in future research in both business and academic areas. Originality/Value: This study's originality stems from its targeted investigation into job-hopping behavior within a specific Malaysian industry. It builds upon established theories and prior research to provide a solid theoretical foundation. Using a quantitative, cross-sectional approach and drawing from previous studies, it brings methodological rigor to the examination of job-hopping behavior. The study's key original contribution lies in its findings, which establish significant relationships between job-hopping and factors like remuneration packages, career advancement, and learning development. These findings offer practical insights for employers in the industry and provide a basis for future research in both business and academic contexts.

High performance of solid electrolyte endowed by SiO2 cross-linking agent towards lithium metal battery

High performance of solid electrolyte endowed by SiO2 cross-linking agent towards lithium metal battery

Doping modulated ion hopping in tantalum oxide based resistive switching memory for linear and stable switching dynamics

Artificial intelligence (AI) has demonstrated that automated machines could eventually replace human labor. However, AI is only settled in restricted environments with high computing resources and power supply. Artificial neural networks are currently implemented at the software level, necessitating the constant retrieval of synaptic weight among devices. Physically composing neural networks with emerging nonvolatile memories (eNVMs) can directly map synaptic weight and accelerate AI computing. Resistive switching memory (RRAM) is a promising in-memory computing unit, but challenges regarding nonideal properties remain unsolved. In particular, nonlinear conductance updating is a major issue that hinders the performance of neural networks with RRAMs. In this study, metal cation doping was introduced to tantalum oxide-based RRAM to reveal the ionic hopping behavior, which is the essence of the resistive switching phenomena. Controlled dopant concentrations and a further understanding of ionic hopping alleviated nonlinear conductance modulation up to ∼1.46, while sustaining proper resistive switching window of ∼10.

Catalytic NO Reduction by Noble-Metal-Free Vanadium-Aluminum Oxide Cluster Anions.

By using state-of-the-art mass spectrometry and guided by the newly discovered single-electron mechanism (SEM; e.g., Ti3+ + 2NO → Ti4+-O•- + N2O), we determined experimentally that the vanadium-aluminum oxide clusters V4-xAlxO10-x- (x = 1-3) can catalyze the reduction of NO by CO and substantiated theoretically that the SEM still prevails in driving the catalysis. This finding marks an important step in cluster science in which a noble metal had been demonstrated to be indispensable in NO activation mediated by heteronuclear metal clusters. The results provide new insights into the SEM in which active V-Al cooperative communication favors the transfer of an unpaired electron from the V atom to NO attached to the Al atom on which the reduction reaction actually takes place. This study provides a clear picture for improving our understanding of related heterogeneous catalysis, and the electron hopping behavior induced by NO adsorption could be a fundamental chemistry for driving NO reduction.

Gen Z Workforce and Job-Hopping Intention: A Study among University Students in Malaysia

Recruiting and retaining top talents are crucial for firm competitive advantage. However, job hopping behaviour has become a significant problem for HR practitioners. In Malaysia, job hopping trend among Generation Z has led to a high turnover rate. It causes damages as firms must endure a significant loss in both financial and non-financial costs. This phenomenon is contributed by several factors that spur them to leave their current employment for other job opportunities. This study has twofold objectives namely: to investigate the relationship between motivational factors and job-hopping intention among Gen Z, and to determine which motivational factors that have significant influence on job hopping intention among Gen Z. This research applied a quantitative method via survey. The items of the questionnaire were adopted from past studies that employed similar instruments that links the job-hopping intentions among Gen Z. Validity and reliability tests had been conducted to test the variables. Data was gathered from 369 respondents who are currently enrolled in public and private universities in Malaysia. Inferential analysis was performed to examine the relationship and influence between motivational factors and job-hopping intention among Gen Z. This study found that both intrinsic and extrinsic factors have significant relationships with job hopping intention among Gen Z. Findings reveal that only four factors have significant impacts on job hopping intention among Gen Z; and achievement factor was found to be the most influential factor in predicting job hopping intention among Gen Z. This study provides insight to government, researchers and organization on the issue related to human resource problem and the possible key factors to motivate and retain them from leaving their current employment. This study enables the organization to find suitable solutions to retain the Gen Z professionals that possess excellent skills and experience for a future growth of the company.

Regulated electron migration in sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly boosted electromagnetic wave absorption

Sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly exhibit highly effective electromagnetic (EM) wave absorption capacity. We demonstrate the influence of regulating electron hopping behaviors on EM characteristics and absorption performance.

Driven responses of periodically patterned superconducting films

We simulate the motion of a commensurate vortex lattice in a periodic lattice of artificial circular pinning sites having different diameters, pinning strengths, and spacings using the time-dependent Ginzburg-Landau formalism. Above some critical DC current density ${J}_{\mathrm{c}}$, the vortices depin, and the resulting steady-state motion then induces an oscillatory electric field $E(t)$ with a defect ``hopping'' frequency ${f}_{0}$, which depends on the applied current density and the pinning landscape characteristics. The frequency generated can be locked to an applied AC current density over some range of frequencies, which depends on the amplitude of the DC as well as the AC current densities. Both synchronous and asynchronous collective hopping behaviors are studied as a function of the supercell size of the simulated system and the (asymptotic) synchronization threshold current densities determined.

Hopping Behavior Mediates the Anomalous Confined Diffusion of Nanoparticles in Porous Hydrogels.

Diffusion is an essential means of mass transport in porous materials such as hydrogels, which are appealing in various biomedical applications. Herein, we investigate the diffusive motion of nanoparticles (NPs) in porous hydrogels to provide a microscopic view of confined diffusion. Based on the mean square displacement from particle tracking experiments, we elucidate the anomalous diffusion dynamics of the embedded NPs and reveal the heterogeneous pore structures in hydrogels. The results demonstrate that diffusive NPs can intermittently escape from single pores through void connective pathways and exhibit non-Gaussian displacement probability distribution. We simulate this scenario using the Monte Carlo method and clarify the existence of hopping events in porous diffusion. The resultant anomalous diffusion can be fully depicted by combining the hopping mechanism and the hydrodynamic effect. Our results highlight the hopping behavior through the connective pathways and establish a hybrid model to predict NP transport in porous environments.

Universal Hopping Motion Protected by Structural Topology.

A scaling law elucidates the universality in nature, presiding over many physical phenomena which seem unrelated. Thus, exploring the universality class of scaling law in a particular system enlightens its physical nature in relevance to other systems and sometimes unearths an unprecedented new dynamic phase. Here, the dynamics of weakly driven magnetic skyrmions are investigated, and its scaling law is compared with the motion of a magnetic domain wall (DW) creep. This study finds that the skyrmion does not follow the scaling law of the DW creep in 2D space but instead shows a hopping behavior similar to that of the particle-like DW in 1D confinement. In addition, the hopping law satisfies even when a topological charge of the skyrmion is removed. Therefore, the distinct scaling behavior between the magnetic skyrmion and the DW stems from a general principle beyond the topological charge. This study demonstrates that the hopping behavior of skyrmions originates from the bottleneck process induced by DW segments with diverging collective lengths, which is inevitable in any closed-shape spin structure in 2D. This work reveals that the structural topology of magnetic texture determines the universality class of its weakly driven motion, which is distinguished from the universality class of magnetic DW creep.

Coaxial Micro Ring Arrays Fabricated on Self‐Assembled Microtube Cavities for Resonant Light Modulation

AbstractComposite optical microcavities, as a versatile platform for light manipulation, have been theoretically revealed that the configuration of concentrically coupled resonant trajectories can significantly enhance the coupling strength, which is however challenging in experimental preparation. Here coaxial whispering gallery resonator chains were designed and fabricated with optically coupled modes split apart by more than the free spectral range (FSR) of the cavity itself. Because such three dimensional (3D) coupled optical systems are extremely difficult to obtain with traditional processing techniques an approach is developed to release and roll‐up pre‐strained, nanostructured silicon nitride membranes into microtubular optical cavities. Parallel nano‐ridges modified on the patterned membranes form into coaxial micro ring arrays after the membrane rolls up into a microtubular structure. Energetic degeneracy, as a consequence of mode splitting exceeding the FSR, leads to interference between bonding and antibonding modes with different mode identities (mode number), resulting in novel light modulation in the form of hybrid super wave modes, which display a distinct hopping behavior resembling linear stretch modes of an oscillator chain.

Granular metallicity as a minimal normal state for superconductivity

We report the evolution of electrical transport properties in insulating FeSe films with electron doping induced by the ionic liquid gating technique. Superconductivity never emerges in the strong insulators with variable-range hopping behavior but is shown to arise once the resistance of the normal state varies as $ln(1/T)$, indicating that this behavior corresponds to the minimal conducting character for developing superconductivity. Our work points toward granular metallicity for the $ln(1/T)$ behavior, suggesting that the emergence of superconductivity requires at least an insulating state containing metallic granules. Moreover, it unravels an electronic segregation in proximity to superconductor-insulator transition, which calls for a comprehensive understanding of this segregated phase.

Job Hopping Behavior among Coffee Shops Employees in Malaysia

Job hopping behavior may have an adverse effect on both employers and employees. For the perspective of employee, there are many factors might influence an employee's decision to job hop including salary dissatisfaction or a better offer elsewhere. The issue of job hopping has been a serious concern for many organizations, and the coffee shops industry is no exception. Therefore, the goal of this research is to discover potential factors influencing to job hopping behavior among coffee shops employees, as well as the relationship of identified factors with job hopping. Job satisfaction, financial and perceived organizational support were the three factors investigated in this research. A total of 231 questionnaires were distributed to employees who are currently working in the coffee shops in Klang Valley area and 215 usable responses returned for a response rate of 93.1 percent. The collected data was analyzed by using Statistical Package for Social Sciences (SPSS) latest version. Results of the job satisfaction (mean= 3.5636), financial (m=3.5622) and perceived organization support (mean=3.5601) shows score lean towards agreement level. Additionally, findings showed that the correlation of all the variables were weak correlated. A multiple regression also was run to predict job hopping behaviour with the three independent variables. Results found that only 6.9% of variance in coffee shops’ employees was explained by job satisfaction, financial and perceived organization support (R² = .069). Even though the findings of this research found that these three variables did not have a direct impact on coffee shop employees' decision to job hop, the findings may provide some guidance and alert coffee shop owners or managers to the importance of these three variables in the coffee shops industry in order to minimize job hopping and will be discussed further in this paper.

Growth, phase transition, and island motion of Au on Ge(111).

Using low energy electron microscopy, Au on Ge(111) is determined to follow a Stranski-Krastanov growth mode consisting of a single layer up to one monolayer (ML), followed by three-dimensional Au-Ge alloy droplets. Near 600°C, we report the first observation of a reversible first-order phase transition that occurs from the (3 × 3)R30° phase to a (1 × 1) phase, which has a coverage of 0.367 ML. The transition gradually occurs through a coexistence region with a temperature range of about 2°C and weakly depends on coverage, varying from 640°C at 1 ML down to 580°C at 0.8 ML. The phase transition is accompanied by phase fluctuations of small domains or the fluctuations of phase boundaries of large domains. At coverage >1 ML and above 250°C, the 3D droplets move with stick-slip hopping behavior that has previously been explained by dissolution of Ge at step edges into the alloy droplet, which then comes to concentration and thermal equilibrium via the island motion.

Changes in Surface Free Energy and Surface Conductivity of Carbon Nanotube/Polyimide Nanocomposite Films Induced by UV Irradiation.

Changes in surface energy and electrical conductivity of polyimide (PI)-based nanocomposite films filled with carbon nanotubes (CNTs) induced by UV exposure are gaining considerable interest in microelectronic, aeronautical, and aerospace applications. However, the underlying mechanism of PI photochemistry and oxidation reactions induced by UV irradiation upon the surface in the presence of CNTs is still not clear. Here, we probed the interplay between CNTs and PIs under UV exposure in the surface properties of CNT/PI nanocomposite films. Changes in contact angles and surface electrical conductivity at the surface of CNT/PI nanocomposite films after UV exposure were measured. The unpaired electron intensity of free radicals generated by UV exposure was monitored by electron paramagnetic resonance. Our study indicates that the covalent interactions between CNTs and radicals generated by UV irradiation on the PI surfaces tailor the surface energy and surface conductivity through anchoring radicals on CNTs. Surprisingly, adding CNTs into PI films exposed to UV leads to antagonistic contributions of dispersion and polar components to the surface energy. The surface electrical conductivity of the CNT/PI nanocomposite films has been improved due to an enhanced hopping behavior with dense π-conjugated CNT sites. To explain the observed changes in surface energy and surface conductivity of CNT/PI nanocomposite films induced by UV exposure, a qualitative model was put forward describing the covalent interactions between UV-induced PI free radicals and CNTs, which govern the chemical nature of surface components. This study is helpful for characterizing and optimizing nanocomposite surface properties by tuning the covalent interactions between components at the nanoscale.

Temperature and electric field effects on the dynamic modes in a spin current auto-oscillator

We systematically study spectral characteristics of emission microwave signal by a spin current nano-oscillator (SCNO) based on $\mathrm{Ta}{\mathrm{O}}_{x}/\mathrm{Py}(3)/\mathrm{Pt}(2)$ trilayers as a function of current, in-plane magnetic field angle, electrostatic gating, and temperature. The current dependence of spectral characteristics shows that such SCNO exhibits a single coherent oscillation mode at low currents, and then transfers into a multimode coexistence regime with several oscillation peaks, related to spatially separated oscillation regions, at high currents. The linewidth of these modes shows an exponential temperature dependence, indicating thermally activated mode transitions or mode hopping behavior among these spatially separated oscillation regions due to the mode coupling caused by strong thermal-magnon-mediated scattering rate at high temperatures. Additionally, electrostatic gating on oscillation frequency shows a temperature-independent behavior, but gets enhanced in the strongly nonlinear oscillation regime. The enhanced phenomenon is caused by a combination of nonlinear frequency redshift and driving current shift due to electric-field modulation of current-induced spin-orbit torques. The demonstrated electric-field and current control of three-terminal SCNO provides an efficient approach to developing electrically tunable microwave generators in radio frequency integrated circuits and spin-wave-based logic gates in magnonic devices.

Enhancing superconductivity of Lu5Rh6Sn18 by atomic disorder

For a number of skutterudite-related cage compounds, such as cubic ${R}_{3}{M}_{4}{\mathrm{Sn}}_{13}$ ($R=\mathrm{Ca}$ or La, $M=\text{transition}$ $d$-electron metal) or tetragonal ${\mathrm{Y}}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$, we have previously reported the impact of various atomic defects in the crystal lattices on the normal-state and superconducting properties of these clathrates. In these quasiskutterudites the nanoscale disorder and/or local inhomogeneity in composition lead to an abnormal increase in the superconducting transition temperature ${T}_{c}$. Here we investigate the impact of atomic defects in the superconductors ${\mathrm{Lu}}_{5\ensuremath{-}\ensuremath{\delta}}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ (tetragonal symmetry $I{4}_{1}/acd$). We have documented that ${\mathrm{Lu}}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ does not crystallize in the assumed stoichiometry but forms a 5-6-18 phase with a Lu deficiency ($\ensuremath{\delta}\ensuremath{\approx}0.5$). Our comprehensive investigations of electronic structure and thermodynamic and electrical transport properties documented a ${T}_{c}$ increase in the more disordered sample (sample 1). The quality of two investigated samples (sample 1 and sample 2) with similar stoichiometry but different local inhomogeneity was obtained by microanalysis and electron transmission microscopy observations. The band structure calculations show a hybridization pseudogap in the electronic bands of stoichiometric ${\mathrm{Lu}}_{5}{\mathrm{Rh}}_{6}{\mathrm{Sn}}_{18}$ at about 0.3 eV in respect to the Fermi level ${\ensuremath{\epsilon}}_{F}$. The ab initio calculations predict the scenario that vacancies could shift this pseudogap towards ${\ensuremath{\epsilon}}_{F}$, which is manifested by the Mott variable-range hopping behavior in the resistivity $\ensuremath{\rho}\ensuremath{\sim}{T}^{\ensuremath{-}1/4}$ of more homogeneous sample 2.

Observation of 2D transport in Sn- and In-doped Bi2−xSbxTe3−ySey topological insulator

Here we report magnetotransport properties of Bi2−xSbxTe3−ySey (BSTS), In- and Sn-doped BSTS single crystals, grown through modified Bridgeman technique. In- and Sn-doped BSTS single crystals show bulk insulation in temperature dependency resistivity measurements and are confirmed from the observed impurity band mediated three dimensional variable-range hopping behavior at low temperatures over virgin BSTS with metallic bulk. Magnetotransport measurements for BSTS and Sn-doped BSTS reveal a zero field sharp positive cusp and is identified as two dimensional (2D) weak antilocalization (WAL) effect, which is the consequence of π Berry phase of the carriers. For In-doped BSTS single crystals, crossover is identified from WAL to weak localization with field variation at low temperatures and also with an increase in temperature from 2 K. For all the single crystals, phase coherence lengths (lϕ) are determined by fitting low field magnetotransport data with Hikami–Larkin–Nagaoka equation. Temperature dependency of phase coherence lengths is described with 2D electron–electron (e–e) and 2D electron–phonon (e–p) interactions for virgin and In-doped BSTS single crystals while for Sn-doped BSTS specimen lϕ(T) follows T−0.53 power law.

Adaptive Expanding Ring Search Based Per Hop Behavior Rendition of Routing in MANETs

Routing protocols in Mobile Ad Hoc Networks (MANETs) operate with Expanding Ring Search (ERS) mechanism to avoid flooding in the network while tracing step. ERS mechanism searches the network with discerning Time to Live (TTL) values described by respective routing protocol that save both energy and time. This work exploits the relation between the TTL value of a packet, traffic on a node and ERS mechanism for routing in MANETs and achieves an Adaptive ERS based Per Hop Behavior (AERSPHB) rendition of requests handling. Each search request is classified based on ERS attributes and then processed for routing while monitoring the node traffic. Two algorithms are designed and examined for performance under exhaustive parametric setup and employed on adaptive premises to enhance the performance of the network. The network is tested under congestion scenario that is based on buffer utilization at node level and link utilization via back-off stage of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). Both the link and node level congestion is handled through retransmission and rerouting the packets based on ERS parameters. The aim is to drop the packets that are exhausting the network energy whereas forward the packets nearer to the destination with priority. Extensive simulations are carried out for network scalability, node speed and network terrain size. Our results show that the proposed models attain evident performance enhancement.