Random Bond Research Articles

Universal Dimensionality of Ferroelectric Domain Walls in Ultrathin Films

AbstractThe dimensionality of dynamic interfaces—domain walls (DWs) —is greatly influenced by symmetry and physical dimensions, irrespective of the microscopic details of the system. To address this fundamental question for the ferroelectric model system, the DW scaling criticality and dimensionality is investigated in ultrathin films of varied ferroelectric materials, compositions, and electrode–ferroelectric interfaces, grown on nominally flat and vicinal substrates. In spite of significant variations among ferroelectric systems, the observed prevalence of 1D DWs is consistent with a random bond disorder, elucidated through a scenario of 2D nucleation and growth‐driven DW creep. These findings highlight the thickness size‐dominated universal behavior of ferroelectric DWs, uncovering fascinating prospects for dimensionally engineered DW‐based nanoelectronics.

Glutathione-mediated copper sulfide nanoplatforms with morphological and vacancy-dependent photothermal catalytic activity for multi-model tannic acid assays

Interface engineering and vacancy engineering play an important role in the surface and electronic structure of nanomaterials. The combination of the two provides a feasible way for the development of efficient photocatalytic materials. Here, we use glutathione (GSH) as a coordination molecule to design a series of CuxS nanomaterials (CuxS-GSH) rich in sulfur vacancies using a simple ultrasonic-assisted method. Interface engineering can induce amorphous structure in the crystal while controlling the formation of porous surfaces of nanomaterials, and the formation of a large number of random orientation bonds further increases the concentration of sulfur vacancies in the crystal structure. This study shows that interface engineering and vacancy engineering can enhance the light absorption ability of CuxS-GSH nanomaterials from the visible to the near-infrared region, improve the efficiency of charge transfer between CuxS groups, and promote the separation and transfer of optoelectronic electron-hole pairs. In addition, a higher specific surface area can produce a large number of active sites, and the synergistic and efficient photothermal conversion efficiency (58.01%) can jointly promote the better photocatalytic performance of CuxS-GSH nanomaterials. Based on the excellent hot carrier generation and photothermal conversion performance of CuxS-GSH under illumination, it exhibits an excellent ability to mediate the production of reactive oxygen species (ROS) through peroxide cleavage and has excellent peroxidase activity. Therefore, CuxS-GSH has been successfully developed as a nanoenzyme platform for detecting tannic acid (TA) content in tea, and convenient and rapid detection of tannic acid is achieved through the construction of a multi-model strategy. This work not only provides a new way to enhance the enzyme-like activity of nanomaterials but also provides a new prospect for the application of interface engineering and vacancy engineering in the field of photochemistry.

Separability Transitions in Topological States Induced by Local Decoherence.

We study states with intrinsic topological order subjected to local decoherence from the perspective of separability, i.e., whether a decohered mixed state can be expressed as an ensemble of short-range entangled pure states. We focus on toric codes and the X-cube fracton state and provide evidence for the existence of decoherence-induced separability transitions that precisely coincide with the threshold for the feasibility of active error correction. A key insight is that local decoherence acting on the "parent" cluster states of these models results in a Gibbs state. As an example, for the 2D (3D) toric code subjected to bit-flip errors, we show that the decohered density matrix can be written as a convex sum of short-range entangled states for p>p_{c}, where p_{c} is related to the paramagnetic-ferromagnetic transition in the 2D (3D) random bond Ising model along the Nishimori line.

Surface Controlled Silicon Nanoparticles Production and Their Effects on High Capacity and High Cyclability of All-Solid-State Lithium-Ion Batteries

Si nanoparticle is expected as anode for high density Lithium-ion batteries as as it facilitates high capacity and high cyclability simultaneously owing to its structural robustness to suppress fracture during cycled (de)lithiation reactions. Direct TEM observation has revealed that the particle size of 150 nm is the threshold for facture and the particles smaller than 150 nm are anticipated to contribute to the structural stability during cycles. However, the surface of silicon nanoparticle is oxidized spontaneously and the specific surface area increases significantly with decreasing the particle size. Accordingly, the specific oxygen content of the Si active material becomes inevitably high for smaller nanoparticles. High oxygen content in Si anode decreases the initial efficiency and capacityas a result of irreversible silicate formation. Therefore, smaller nanoparticle with a limited amount of oxidation would be ideal and necessary to attain high capacity and high cyclability. However, there is few report on the approach to suppress oxidation of smaller silicon nanoparticles and discuss the effect of size and oxygen content separately. Also, no general understanding of the effect of the particle size and oxygen for the case of all-solid-state batteries (ASSBs). In this work, we have produced Si nanoparticles with differently controlled size and oxygen content by plasma flash evaporation (PFE) from low-cost powder feedstock, and the effect of characteristic oxide surface structure on the battery performance of ASSBs with Argyrodite electrolyte has been identified.We have successfully produced the nanoparticles as small as 20 nm and reduced the oxygen content x in SiOx representation from the standard amount of 0.24 to 0.049. As a result, the initial discharged capacity can be improved by 110% while attaining similar cyclabilities. When we compare the nanoparticles with different sizes ranging from 20 nm to 165 nm and having small oxygen content x < 0.05, although the initial discharged capacities are almost the same for these particles, only the particle with 165 nm shows rapid capacity decay in 10 cycles, whereas the 20 nm and 84 nm particles tend to maintain the capacity similarly. This confirms that the particles smaller than 100 nm are effective to maintain high capacity also in ASSBs under a low 0.1 C-rate condition. Furthermore, XPS analysis revealed that the surface of the particles with less oxidation is composed of suboxide Si-O bond oxide preferentially and the amount of Si-O4 bond is less than the conventional particles covered by the oxide shell, with which the Si-O bond ratio is described by the conventional random bond model. No apparent dependence of the capacity with the amount of Si-O4 bond. However, the surface oxide shell thickness estimated by the Si-O bond amount and the total oxygen content has shown a clear linear correlation with the charged capacity, irrespective of the particle size. This suggests that the surface oxide thickness affects significantly the amount of the lithiation reaction and is ideally as thin as possible to attain high capacity, especially for the case of ASSBs.

Self-organized criticality of magnetic avalanches in disordered ferrimagnetic material.

We observe multiple steplike jumps in a Dy-Fe-Ga-based ferrimagnetic alloy in its magnetic hysteresis curve at 2K. The observed jumps are found to have a stochastic character with respect to their magnitude and the field position, and the jumps do not correlate with the duration of the field. The distribution of jump size follows a power law variation indicating the scale invariance nature of the jumps. We have invoked a simple two-dimensional random bond Ising-type spin system to model the dynamics. Our computational model can qualitatively reproduce the jumps and their scale-invariant character. It also elucidates that the flipping of antiferromagnetically coupled Dy and Fe clusters is responsible for the observed jumps in the hysteresis loop. These features are described in terms of the self-organized criticality.

On the role of random bond in spin-crossover compounds

On the role of random bond in spin-crossover compounds

Quasiparticle excitations in a one-dimensional interacting topological insulator: Application for dopant-based quantum simulation

We study the effects of electron-electron interactions on the charge excitation spectrum of the spinful Su-Schrieffer-Heeger (SSH) model, a prototype of a 1D bulk obstructed topological insulator. In view of recent progress in the fabrication of dopant-based quantum simulators we focus on experimentally detectable signatures of interacting topology in finite lattices. To this end we use Lanczos-based exact diagonalization to calculate the single-particle spectral function in real space which generalizes the local density of states to interacting systems. Its spatial and spectral resolution allows for the direct investigation and identification of edge states. By studying the non-interacting limit, we demonstrate that the topological in-gap states on the boundary are robust against both finite-size effects as well as random bond and onsite disorder which suggests the feasibility of simulating the SSH model in engineered dopant arrays in silicon. While edge excitations become zero-energy spin-like for any finite interaction strength, our analysis of the spectral function shows that the single-particle charge excitations are gapped out on the boundary. Despite the loss of topological protection we find that these edge excitations are quasiparticle-like as long as they remain within the bulk gap. Above a critical interaction strength of $U_c\approx 5 t$ these quasiparticles on the boundary loose their coherence which is explained by the merging of edge and bulk states. This is in contrast to the many-body edge excitations which survive the limit of strong coupling, as established in the literature. Our findings show that for moderate repulsive interactions the non-trivial phase of the interacting SSH model can be detected through remnant signatures of topological single-particle states using single-particle local measurement techniques such as scanning tunneling spectroscopy.

Measurement-induced entanglement transition in a two-dimensional shallow circuit

We prepare two dimensional states generated by shallow circuits composed of (1) one layer of two-qubit CZ gate or (2) a few layers of two-qubit random Clifford gate. After measuring all of the bulk qubits, we study the entanglement structure of the remaining qubits on the one dimensional boundary. In the first model, we observe that the competition between the bulk X and Z measurements can lead to an entanglement phase transition between an entangled volume law phase and a disentangled area law phase. We numerically evaluate the critical exponents and generalize this idea to other qudit systems with local Hilbert space dimension larger than 2. In the second model, we observe the entanglement transition by varying the density of the two-qubit gate in each layer. We give an interpretation of this transition in terms of random bond Ising model in a similar shallow circuit composed of random Haar gates.

Quantum information spreading in random spin chains

We study the spreading of quantum correlations and information in a one-dimensional quantum spin chain with critical disorder as encoded in an infinite randomness fixed point. Specifically, we focus on the dynamics after a quantum quench of the R\'enyi entropies, of the mutual information and of the entanglement negativity in the prototypical XXZ spin chain with random bonds and anisotropy parameters. We provide analytic predictions in the scaling regime based on real-space renormalization group methods. We support these findings through numerical simulations in the non-interacting limit, where we can access the scaling regime.

Displacement Correlations in Disordered Athermal Networks

We derive exact results for correlations in the displacement fields \(\{ \delta \mathbf {r} \} \equiv \{ \delta r_{\mu = x,y} \}\) in near-crystalline athermal systems in two dimensions. We analyze the displacement correlations produced by different types of microscopic disorder, and show that disorder at the microscopic scale gives rise to long-range correlations with a dependence on the system size L given by \(\langle \delta r_{\mu } \delta r_{\nu } \rangle \sim c_{\mu \nu }(r/L,\theta )\). In addition, we show that polydispersity in the constituent particle sizes and random bond disorder give rise to a logarithmic system size scaling, with \(c_{\mu \nu }(\rho ,\theta ) \sim \text {const}_{\mu \nu } - \text {a}_{\mu \nu }(\theta )\log \rho + \text {b}_{\mu \nu }(\theta ) \rho ^{2} \) for \(\rho ~(=r/L) \rightarrow 0\). This scaling is different for the case of displacement correlations produced by random external forces at each vertex of the network, given by \(c^{f}_{\mu \nu }(\rho ,\theta ) \sim \text {const}^{f}_{\mu \nu } -( \text {a}^{f}_{\mu \nu }(\theta ) + \text {b}^{f}_{\mu \nu }(\theta ) \log \rho ) \rho ^2 \). Additionally, we find that correlations produced by polydispersity and the correlations produced by disorder in bond stiffness differ in their symmetry properties. Finally, we also predict the displacement correlations for a model of polydispersed soft disks subject to external pinning forces, that involve two different types of microscopic disorder. We verify our theoretical predictions using numerical simulations of polydispersed soft disks with random spring contacts in two dimensions.

Depinning and flow of a vortex line in a uniaxial random medium

We study numerically and analytically the dynamics of a single directed elastic string driven through a three-dimensional disordered medium. In the quasistatic limit the string is super-rough in the direction of the driving force, with roughness exponent ${\ensuremath{\zeta}}_{\ensuremath{\parallel}}=1.25\ifmmode\pm\else\textpm\fi{}0.01$, dynamic exponent ${z}_{\ensuremath{\parallel}}=1.43\ifmmode\pm\else\textpm\fi{}0.01$, correlation-length exponent $\ensuremath{\nu}=1.33\ifmmode\pm\else\textpm\fi{}0.02$, depinning exponent $\ensuremath{\beta}=0.24\ifmmode\pm\else\textpm\fi{}0.01$, and avalanche-size exponent ${\ensuremath{\tau}}_{\ensuremath{\parallel}}=1.09\ifmmode\pm\else\textpm\fi{}0.03$. In the transverse direction we find ${\ensuremath{\zeta}}_{\ensuremath{\perp}}=0.5\ifmmode\pm\else\textpm\fi{}0.01, {z}_{\ensuremath{\perp}}=2.27\ifmmode\pm\else\textpm\fi{}0.05$, and ${\ensuremath{\tau}}_{\ensuremath{\perp}}=1.17\ifmmode\pm\else\textpm\fi{}0.06$. Our results show that transverse fluctuations do not alter the critical exponents in the driving direction, as predicted by the planar approximation (PA) proposed by Ertas and Kardar (EK) [Phys. Rev. B 53, 3520 (1996)]. We check the PA for the measured force-force correlator, comparing to the functional renormalization-group and numerical simulations. Both random-bond (RB) and random-field (RF) disorder yield a single universality class, indistinguishable from the one of an elastic string in a two-dimensional random medium. While relations ${z}_{\ensuremath{\perp}}={z}_{\ensuremath{\parallel}}+1/\ensuremath{\nu}$ and $\ensuremath{\nu}=1/(2\ensuremath{-}{\ensuremath{\zeta}}_{\ensuremath{\parallel}})$ of EK are satisfied, the transversal movement is that of a Brownian, with a clock set locally by the forward movement. This implies ${\ensuremath{\zeta}}_{\ensuremath{\perp}}=(2\ensuremath{-}d)/2$, distinct from EK. Finally, at small driving velocities the distribution of local parallel displacements has a negative skewness, while in the transverse direction it is a Gaussian. For large scales, the system can be described by anisotropic effective temperatures defined from generalized fluctuation-dissipation relations. In the fast-flow regime the local displacement distributions become Gaussian in both directions and the effective temperatures vanish as ${T}_{\mathtt{eff}}^{\ensuremath{\perp}}\ensuremath{\sim}1/v$ and ${T}_{\mathtt{eff}}^{\ensuremath{\parallel}}\ensuremath{\sim}1/{v}^{3}$ for RB disorder and as ${T}_{\mathtt{eff}}^{\ensuremath{\perp}}\ensuremath{\approx}{T}_{\mathtt{eff}}^{\ensuremath{\parallel}}\ensuremath{\sim}1/v$ for RF disorder.

Autonomous Gluing Shoe Sole Based on Pointcloud Data

Adhesive gluing is an important step in leather shoe manufacturing, helping the shoe parts to stick together, especially between the sole and the upper body of the shoe. However, this task is still greatly relied on manual operation and robot teaching by playback. It is difficult that those tasks produce high productivity because the kinds of shoes to be performed are up to several thousands and the shoe itself is a non-rigid object, which is easy to be twisted during the manufacturing process. There are two kinds of shoe: flat objects that can be classified as 2D objects; however, for high heels, they should be considered as 3D objects. Therefore, the definition of the gluing trajectory is more complex for high heels soles. In order to ensure the satisfactory quality, the adhesive tip should be perpendicular to the sole at the point of the trajectory. This research presents a practical strategy for an automated gluing task in footwear industry by using a 6DOF industrial robot and RGB-D camera. By using 3D camera, when a random soling bond is positioned inside the robot working area, the 3D pointcloud boundary contour data of the shoe sole is extracted and interpolated for accurate and smooth trajectory generation then the manipulator will autonomously execute the trajectory tracing task. The efficiency of the system in terms of time, stability, and accuracy is proven through experiments.

Improvement of electric insulation in dielectric layered perovskite nickelate films via fluorination

Epitaxial films of La3/2Sr1/2NiOxFy with a wide range of fluorine content (y), 0.4–3, were prepared. The fluorinated film exhibited high electric insulation due to the large and random bond distortions provided by the fluorination.

A Hypothetical Approach to Cosmic Inflation Incorporating Binary Entropy

The current paper presents an alternative hypothesis for the termination of cosmic inflation based on Huang&amp;rsquo;s model of spacetime involving the movement of a superfluid through a random resistor network. Using this model, we previously derived a mathematical relationship between the velocity of a reference frame and the probability that a random bond is intact. As an extension of this finding, the permutations of open and closed bonds are now shown to represent potential microstates, thus providing a means of relating motion within the network to binary entropy. Applying this concept to cosmic inflation, termination of this process is an expected consequence of the changes in binary entropy associated with the increasing velocity of expansion.

Quantum wetting transition in the one-dimensional transverse-field Ising model with random bonds

The quantum wetting transition in the one-dimensional transverse-field Ising model with random bonds is studied. Opposite boundary fields are applied at the two ends of the Ising chain. The interface between two domains with oppositely oriented magnetization is localized near the boundary or in the middle of the chain. The wetting transition refers to the phase transition of localization and delocalization of the interface. The tuning parameter ${h}_{L}$ is the boundary field at one end, e.g., the left end. At the transition point ${h}_{L}={h}_{w}$, the wetting transition occurs. First, we study the wetting transition with one defect bond. It is a first-order transition, and the interface jumps from the left end of the chain to the defect bond at the transition point. Second, we study the wetting transition with two defect bonds and find that the weaker defect bond dominates the phase transition. The wetting transition is still first order, and the interface is localized at the left end of the chain or at the weaker defect bond. Lastly, the random bond case is studied. The random bonds have a rectangular distribution. The wetting transition is still first order. The finite-size effects are studied. The statistics of the transition points and the energy gaps are obtained. We study lattices with sizes $N=100$, 150, 200, 250, 300, and 350. The deviation of the phase transition points ${h}_{w}$ does not decrease as the lattice size increases. It is argued that the transition point is sample dependent, i.e., the variation in the transition point ${h}_{w}$ does not approach zero, even at the thermodynamic limit.

Effect of correlated oxide electrodes on disorder pinning and thermal roughening of ferroelectric domain walls in epitaxial PbZr0.2Ti0.8O3 thin films

We report the competing effects of disorder pinning and thermal roughening on ferroelectric domain walls as a function of temperature in epitaxial $\mathrm{Pb}{\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}{\mathrm{O}}_{3}$ thin films deposited on (001) $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrates buffered by three types of correlated oxide electrodes, ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3}$, $\mathrm{LaNi}{\mathrm{O}}_{3}$, and $\mathrm{SrIr}{\mathrm{O}}_{3}$. Piezoresponse force microscopy studies show that the 50-nm $\mathrm{Pb}{\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}{\mathrm{O}}_{3}$ films are uniformly polarized in the as-grown states, with the patterned domain structures persisting above 700 \ifmmode^\circ\else\textdegree\fi{}C. For all three types of films, the domain wall roughness is dominated by two-dimensional (2D) random bond disorder at room temperature, and transitions to 1D thermal roughening upon heating. The roughness exponent $\ensuremath{\zeta}$ increases progressively from 0.3 to 0.5 within a temperature window that depends on the bottom conducting oxide type, from which we extracted the distribution of disorder pinning energy. We discuss the possible origins of the disorder pinning and the effect of the correlated oxide electrodes on the energy landscape of DW motion.

Structural correlation of GeTeSeGa system by XRD and far-infrared spectroscopy

The structural properties of quaternary Ge10Te80Se10-xGax (x = 0 to 10) glassy alloy have been studied with XRD (X-ray diffraction) and FTIR (Fourier transform infrared) spectroscopy. The position of FSDP (first sharp diffraction peak) (2θ) and its FWHM (full width half maxima) have been utilized to estimate the local structure parameters of FSDP like repeating distance y and structural correlation length (L). The far-infrared (IR) transmission spectra of Ge10Te80Se10-xGax (x = 0, 2, 4, 6, 8, 10) have been analysed in the range 30–300 cm−1 to study the formation of bonds using chain crossing model, random covalent network model and chemical bond approach. The theoretical calculations have been executed for bond energies, force constants, wave number, etc., for probable bonds, and the results justify the experimental values. The present study contributes to the understanding of the composition-dependent structural property relationship of chalcogenide glasses.

Bond-random model of spin-crossover compounds: similarities and differences from spin glasses

The Ising-like model of spin-crossover solid compounds with random bonds has been studied by the mean-field (infinite range) replica symmetry approximation. An exact solution to the problem is found and analyzed. Interestingly, the temperature stability region at selected intermolecular couplings and standard deviations is quite wide.

Thermal properties of rung-disordered two-leg quantum spin ladders: Quantum Monte Carlo study.

A two-leg quenched random bond disordered antiferromagnetic spin-1/2 Heisenberg ladder system is investigated by means of stochastic series expansion quantum Monte Carlo (QMC) method. Thermal properties of the uniform and staggered susceptibilities, the structure factor, the specific heat, and the spin gap are calculated over a large number of random realizations in a wide range of disorder strength. According to our QMC simulation results, the considered system has a special temperature point at which the specific heat takes the same value regardless of the strength of the disorder. Moreover, the uniform susceptibility is shown to display the same character except for a small difference in the location of the special point. Finally, the spin gap values are found to decrease with increasing disorder parameter and the smallest gap value found in this study is well above the weak coupling limit of the clean case.

Universality in the three-dimensional random bond quantum Heisenberg antiferromagnet

The three-dimensional quenched random bond diluted $({J}_{1}\ensuremath{-}{J}_{2})$ quantum Heisenberg antiferromagnet is studied on a simple-cubic lattice. Using extensive stochastic series expansion quantum Monte Carlo simulations, we perform very long runs for an $L\ifmmode\times\else\texttimes\fi{}L\ifmmode\times\else\texttimes\fi{}L$ lattice up to $L=48$. By employing a standard finite-size scaling method, the numerical values of the N\'eel temperature are determined with high precision as a function of the coupling ratio $r={J}_{2}/{J}_{1}$. Based on the estimated critical exponents, we find that the critical behavior of the considered model belongs to the pure classical three-dimensional $O(3)$ Heisenberg universality class.