Classical Glasses Research Articles

Localized Dynamics in the Floquet Quantum East Model.

We introduce and study the discrete-time version of the quantum East model, an interacting quantum spin chain inspired by simple kinetically constrained models of classical glasses. Previous work has established that its continuous-time counterpart displays a disorder-free localization transition signaled by the appearance of an exponentially large (in the volume) family of nonthermal, localized eigenstates. Here we combine analytical and numerical approaches to show that (i)the transition persists for discrete times, in fact, it is present for any finite value of the time step apart from a zero measure set; (ii)it is directly detected by following the nonequilibrium dynamics of the fully polarized state. Our findings imply that the transition is currently observable in state-of-the-art platforms for digital quantum simulation.

The Harmonic and Gaussian Approximations in the Potential Energy Landscape Formalism for Quantum Liquids.

The potential energy landscape (PEL) formalism has been used in the past to describe the behavior of classical low-temperature liquids and glasses. Here, we extend the PEL formalism to describe the behavior of liquids and glasses that obey quantum mechanics. In particular, we focus on the (i) harmonic and (ii) Gaussian approximations of the PEL, which have been commonly used to describe classical systems, and show how these approximations can be applied to quantum liquids/glasses. Contrary to the case of classical liquids/glasses, the PEL of quantum liquids is temperature-dependent, and hence, the main expressions resulting from approximations (i) and (ii) depend on the nature (classical vs quantum) of the system. The resulting theoretical expressions from the PEL formalism are compared with results from path-integral Monte Carlo (PIMC) simulations of a monatomic model liquid. In the PIMC simulations, every atom of the quantum liquid is represented by a ring-polymer. Our PIMC simulations show that at the local minima of the PEL (inherent structures, or IS), sampled over a wide range of temperatures and volumes, the ring-polymers are collapsed. This considerably facilitates the description of quantum liquids using the PEL formalism. Specifically, the normal modes of the ring-polymer system/quantum liquid at an IS can be calculated analytically if the normal modes of the classical liquid counterpart are known (as obtained, e.g., from classical MC or molecular dynamics simulations of the corresponding atomic liquid).

Very Large Pore Mesoporous Bioactive Silicate Glasses: Comparison of Behavior toward Classical Mesoporous Bioactive Glasses in Terms of Drug Loading/Release and Bioactivity.

Considering the increase in patients who suffer from osteoporosis and the bone defects that occur in these patients, bone tissue regeneration is a promising option to solve this problem. To achieve a synergistic effect between the synthesis of a proper structure and bioactive/pharmaceutical activity, ions with a physiological effect can be added to silica structures, such as Ca2+, thanks to its bioactive behavior, and Ga3+ for its antibacterial and anticancer action. In this work, the synthesis of large pore mesoporous silica (LPMS), potential bioactive glasses containing Ca2+ and Ga3+, has been studied. Corresponding structures, in terms of composition, have been synthesized following the Sol-Gel EISA (Evaporation Induced Self-Assembly) process (obtaining Classical Mesoporous Silica, MS). Pore structure characterization of LPMSs and MSs has been performed using N2 adsorption/desorption and Hg-porosimetry, showing the presence of pores for LPMSs in the range of 20-60 and 200-600 nm. Nisin, a polycyclic antibacterial peptide, has been used for load tests. The load and release tests performed highlight a higher loading and releasing, doubled for LPMSs if compared to MSs. To confirm the maintenance of the structure of LPMSs and their mechanical strength and resistance, scanning electron microscopy images were acquired before and after release tests. Ca and Ga release in SBF has been studied through inductively coupled plasma-optical emission spectroscopy (ICP-OES), showing a particularly high release of these ions performed with LPMSs. The bioactive behavior of Ca-containing structures has been confirmed using FT-IR (Fourier-transform infrared spectroscopy), SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy), and X-ray powder diffraction (XRDP). In conclusion, LPMSs showed better loading and releasing properties compared with classical MS and better release in terms of active ions. In addition, it has also been demonstrated that LPMSs have bioactive behavior (a well-known characteristic of MSs).

Precise control over gas-transporting channels in zeolitic imidazolate framework glasses

Porous metal–organic frameworks have emerged to resolve important challenges of our modern society, such as CO2 sequestration. Zeolitic imidazolate frameworks (ZIFs) can undergo a glass transition to form ZIF glasses; they combine the liquid handling of classical glasses with the tremendous potential for gas separation applications of ZIFs. Using millimetre-sized ZIF-62 single crystals and centimetre-sized ZIF-62 glass, we demonstrate the scalability and processability of our materials. Further, following the evolution of gas penetration into ZIF crystals and ZIF glasses by infrared microimaging techniques, we determine the diffusion coefficients and changes to the pore architecture on the ångström scale. The evolution of the material on melting and processing is observed in situ on different length scales by using a microscope-coupled heating stage and analysed microstructurally by transmission electron microscopy. Pore collapse during glass processing is further tracked by changes in the volume and density of the glasses. Mass spectrometry was utilized to investigate the crystal-to-glass transition and thermal-processing ability. The controllable tuning of the pore diameter in ZIF glass may enable liquid-processable ZIF glass membranes for challenging gas separations.

Electrochromic Glass Design with Solar Energy

With the effect of the use of non-renewable energy sources, our world is facing the danger ofglobal warming. The use of fossil fuels increases the rate of carbon dioxide emitted into the atmosphere,and thus, global warming, unfortunately, brings climate changes with it. Minimizing this danger can onlybe achieved by turning humanity towards renewable energy sources. Solar energy is a reliable,environmentally friendly and inexpensive source. The aim of this study is to perform the electrochromicglass by using solar energy without any electricity costs and thus to encourage people to more renewableenergy technologies. In this study, it is desired to present a new technology design that is an alternative tothe classical window glasses used in our country by using solar energy. The solar panel converts the sun'senergy into electrical energy by using solar energy, and with this electrical energy, the opaqueelectrochromic glass changes color and becomes transparent. Thus, the glass makes the interior of the roomshow with this color change. This system, which works with a photovoltaic panel, operates theelectrochromic glass with solar energy without the need for extra energy. For example, with this system, italso eliminates the need for curtains or roller blinds used in working and living areas and provide ease ofuse according to the desired conditions. This system can be used not only for this purpose, but alsoanywhere that is required for smart glass design and has solar energy potential. For this study,electrochromic smart glass obtained by placing polymer dispersed liquid crystal (PDLC) smart materialand this material was sandwiched between indium tin oxide window films with the help of Polyvinyl butyral(PVB) layer. This electrochromic glass system is designed by connecting the connection cable and the onoff switch cable to the photovoltaic panel. In this study, electrochromic glass performance was tried to beanalyzed depending on the exposure time of the photovoltaic panel in the sun.

Understanding the Rheology of Polymer–Polymer Interfaces Covered with Janus Nanoparticles: Polymer Blends versus Particle Sandwiched Multilayers

Interfacial rheology is crucial in dictating morphology and ultimate properties of particle-stabilized polymer blends, but is challenging to be determined. In this study, a fully polymeric dumbbell-shaped Janus nanoparticle (JNP) of polymethyl methacrylate (PMMA) and polystyrene (PS) spheres with equal sizes (∼80 nm) was prepared and used as an efficient compatibilizer for PMMA/PS blends. The JNPs were preferentially localized at the PMMA/PS interface, thereby reducing the interfacial tension and refining the morphology in both droplet-matrix and co-continuous type blends, whereby a JNP concentration ∼2.5 wt % is sufficient to reach a saturation in droplet size reduction due to compatibilization. Based on the linear viscoelastic moduli and corresponding relaxation spectra (H(τ)*τ) of JNP-compatibilized droplet-matrix blends, besides the droplet shape relaxation time (τF), a longer relaxation time (τβ), typically related to interfacial viscoelasticity, was readily identified. The dependence of τβ on the JNP concentration (WJNPs) was significantly dominated by the droplet size reduction induced by the JNP compatibilization, with τβ decreasing with increasing WJNPs. The viscoelastic properties extracted from τβ typically originate from a combination of gradients in interfacial tension due to the particle redistribution at the droplet interface (Marangoni stresses) and the deviatoric stresses of intrinsic rheological origin. The latter originate from the intrinsic viscoelasticity of the particle-laden interface, which is enhanced by particle jamming and particle–polymer interactions, such as entanglements between chains from the polymeric spheres and those penetrating from the bulk into the spheres. To address the challenge of isolating these contributions, a JNP-sandwiched PMMA/PS multilayer structure was designed to exclude the effect of Marangoni stresses and droplet curvature, thus having no τF but a new relaxation (τ′β), which characterizes the contribution of intrinsic interfacial viscoelasticity. The τ′β was observed to increase with JNP coverage (Σ) following the Vogel–Fulcher–Tammann model that is typically used to describe the divergent behavior of the “cage” effect in classical colloidal glasses. Moreover, a multimode Maxwell model fitting allows to split the interfacial relaxation into the confined diffusion of JNPs within their cage and the entanglements between the JNPs and the bulk.

Spatiotemporal heterogeneity of entanglement in many-body localized systems

We propose a spatio-temporal characterization of the entanglement dynamics in many-body localized (MBL) systems, which exhibits a striking resemblance with dynamical heterogeneity in classical glasses. Specifically, we find that the relaxation times of local entanglement, as measured by the concurrence, are spatially correlated yielding a dynamical length scale for quantum entanglement. As a consequence of this spatio-temporal analysis, we observe that the considered MBL system is made up of dynamically correlated clusters with a size set by this entanglement length scale. The system decomposes into compartments of different activity such as active regions with fast quantum entanglement dynamics and inactive regions where the dynamics is slow. We further find that the relaxation times of the on-site concurrence become broader distributed and more spatially correlated, as disorder increases or the energy of the initial state decreases. Through this spatio-temporal characterization of entanglement, our work unravels a previously unrecognized connection between the behavior of classical glasses and the genuine quantum dynamics of MBL systems.

Free energy of the quantum Sherrington–Kirkpatrick spin-glass model with transverse field

We consider the quantum Sherrington–Kirkpatrick (SK) spin-glass model with a transverse field and provide a formula for its free energy in the thermodynamic limit, valid for all inverse temperatures β > 0. To characterize the free energy, we use the path integral representation of the partition function and approximate the model by a sequence of finite-dimensional vector-spin glasses with Rd-valued spins. This enables us to use the results of Panchenko who generalized [Ann. Probab. 46(2), 829–864 (2018); ibid, 46(2), 865–896 (2018)] the Parisi formula to classical vector-spin glasses. As a consequence, we can express the thermodynamic limit of the free energy of the quantum SK model as the d → ∞ limit of the free energies of the d-dimensional approximations of the model.

Ionic glasses: Structure, properties and classification

Due to the absence of microstructure and virtually infinite compositional versatility, glassy materials are perfect candidates for rational methods to predict structure-property relationships. In the most common models of glass structure, a three-dimensional network backbone and less-localized interstitial species are taken as the fundamental constituents of a glass. Such theoretical frameworks break down for the wide range of glass-forming compositions in which covalent bonding does not percolate and, therefore, there is no network in the classical sense. Most prominently, this applies to the class of ionic glasses, presently emerging as a separate class of amorphous materials, which includes classical invert glasses, geometrically frustrated compounds, mixtures of simple salts and ionic liquids, and organic–inorganic hybrids. Here, we will critically review ionic glasses as a distinct group of materials in which structural predictions are complicated by the dominance of long-range bonding interactions which lack directionality. First, we will reassess Zachariasen’s and Hägg’s rules for conventional glass formation in an attempt to broaden the current understanding of glass formation to include ionic glasses. By reviewing the compositions and properties of many simple and complex glass-forming salts, we discern the commonalities shared by ionic glasses and their unique characteristics as compared to other classes of glass. Specifically, we discuss the importance of non-percolating topology to dynamic properties such as mechanical behavior, ionic conductivity, relaxation processes and crystallization. We also demonstrate the relevance of the adjacent fields of ionic liquids and amorphous metal organic frameworks, and highlight possibilities for fruitful interdisciplinary exchange. The structure of ionic glasses, being dominated by Coulombic interactions, lends itself to high compositional flexibility and therefore, creates significant opportunities in the search for optical materials with enhanced transmission windows, fast ion conductors, phase-change materials, or, e.g ., adapted solders, hermetic seals and dielectric insulators. • The field of ionic glasses is reviewed with a focus on structure and properties. • Classification criteria are proposed. • Invert, halide, oxoanionic, halide-oxide and superionic glasses are included. • Links are drawn to the adjacent fields of ionic liquids and metal organic framework glasses.

Quantum East Model: Localization, Nonthermal Eigenstates, and Slow Dynamics

We study in detail the properties of the quantum East model, an interacting quantum spin chain inspired by simple kinetically-constrained models of classical glasses. Through a combination of analytics, exact diagonalization and tensor-network methods we show the existence of a transition, from a fast to a slow thermalization regime, which manifests itself throughout the spectrum. On the slow side, by exploiting the localization of the ground state and the form of the Hamiltonian, we explicitly construct a large (exponential in size) number of non-thermal states which become exact finite-energy-density eigenstates in the large-size limit, as expected for a true phase transition. A ``super-spin'' generalization allows us to find a further large class of area-law states proved to display very slow relaxation. These states retain memory of their initial conditions for extremely long times. Our numerical analysis reveals that the localization properties are not limited to the ground state and that} many eigenstates have large overlap with product states and can be approximated well by matrix product states at arbitrary energy densities. The mechanism that induces localization to the ground state, and hence the non-thermal behavior of the system, can be extended to a wide range of models including a number of simple spin chains. We discuss implications of our results for slow thermalization and non-ergodicity more generally in disorder-free systems with constraints and we give numerical evidence that these results may be extended to two dimensional systems.

Classical glasses, black holes, and strange quantum liquids

From the dynamics of a broad class of classical mean-field glass models one may obtain a quantum model with finite zero-temperature entropy, a quantum transition at zero temperature, and a time-reparametrization (quasi-)invariance in the dynamical equations for correlations. The low eigenvalue spectrum of the resulting quantum model is directly related to the structure and exploration of metastable states in the landscape of the original classical glass model. This mapping reveals deep connections between classical glasses and the properties of SYK-like models.

Chalcogenide Glasses

Chalcogenide glasses, which are among the technologically very important materials, contain at least one chalcogen element as a major constituent and their utilization ranges from infrared optics applications to phase–change, optical–electrical data–recording. The interest to spectacle glasses exhibiting transparency in the infrared region of the optical spectrum coincides with the mid–twentieth century. Firstly, heavy metal oxides were investigated and the transparency limit was extended from 3–5 μm (classical oxide glasses) to 7–8 μm wavelength. The widespread usage of infra–red (IR) optics in the 20 th century has led to the need for new IR materials and to increase the IR transparency limit over 8 μm and scientists have tried chemical compositions of S, Se and Te in the 6 th group of the periodic table. Compared to oxide glasses, their mechanical strength and thermal stability are considerably lower and the calorimetric glasses form a new glass group with semiconductor properties. In this article, a brief overview of the definition, historical development, structure, properties and potential applications of chalcogenide glasses dating back to the early 1950s.

Mesoporous bioactive glasses doped with cerium: Investigation over enzymatic-like mimetic activities and bioactivity

In this work, we investigate the ability of mesoporous bioactive glasses (MBGs) modified with cerium ions (Ce3+/Ce4+) to act as catalase and superoxide dismutase (SOD) mimetic materials. We have previously reported that the catalytic properties of bioactive Ce-containing glasses based on 45S5 Bioglass® and synthesized via melting are influenced by: i) composition (presence/absence of P2O5); ii) Ce3+/Ce4+ molar ratio. The introduction of cerium species drastically decreased the bioactivity in terms of Hydroxyapatite formation during bioactivity tests in vitro. We thus decided to add cerium to MBGs, a class of glasses with improved bioactivity with respect to classical molten glasses. MBGs exhibit a high surface area and their reactivity is increased with respect to the molten glasses; they are able to induce the formation of Hydroxyapatite over the surface within shorter times with respect to the 45S5. The catalase and SOD mimetic activity tests revealed that the Ce-MGBs are able to act as mimetic materials for the two enzymes. Both Infrared Spectroscopy and X-ray diffraction analysis have confirmed the presence of Hydroxyapatite over both 80SiO2–15CaO–5P2O5, and 80SiO2–20CaO MBGs samples modified by 5.3% mol of CeO2; simultaneously the glasses maintain a good catalase activity. Moreover, the 80SiO2–15CaO–5P2O5 potential bioactive glasses showed SOD mimetic activity. These results highlight that it is possible to obtain a glass with both antioxidant and bioactivity properties.

Quantum Slow Relaxation and Metastability due to Dynamical Constraints.

One of the general mechanisms that give rise to the slow cooperative relaxation characteristic of classical glasses is the presence of kinetic constraints in the dynamics. Here we show that dynamical constraints can similarly lead to slow thermalization and metastability in translationally invariant quantum many-body systems. We illustrate this general idea by considering two simple models: (i)a one-dimensional quantum analogue to classical constrained lattice gases where excitation hopping is constrained by the state of neighboring sites, mimicking excluded-volume interactions of dense fluids; and (ii)fully packed quantum dimers on the square lattice. Both models have a Rokhsar-Kivelson (RK) point at which kinetic and potential energy constants are equal. To one side of the RK point, where kinetic energy dominates, thermalization is fast. To the other, where potential energy dominates, thermalization is slow, memory of initial conditions persists for long times, and separation of timescales leads to pronounced metastability before eventual thermalization. Furthermore, in analogy with what occurs in the relaxation of classical glasses, the slow-thermalization regime displays dynamical heterogeneity as manifested by spatially segregated growth of entanglement.

Signatures of many-body localisation in a system without disorder and the relation to a glass transition

We study a quantum spin system—adapted from a facilitated spin model for classical glasses—with local bilinear interactions and without quenched disorder which seems to display characteristic signatures of a many-body localisation (MBL) transition. From direct diagonalisation of small systems, we find a change in certain dynamical and spectral properties at a critical value of a coupling, from those characteristic of a thermalising phase to those characteristic of a MBL phase. The system we consider is known to have a quantum phase transition in its ground-state in the limit of large size, related to a first-order active-to-inactive phase transition in the stochastic trajectories of an associated classical model of glasses. Our results here suggest that this first-order transition in the low-lying spectrum may influence the rest of the spectrum of the system in the large size limit. These findings may help understand the connection between MBL and structural glass transitions.

Comparing Occlusion Method by Display Blanking to Occlusion Goggles

The paper reports on an experiment, which compares the occlusion methods: display blanking (via an Android application) and classical occlusion glasses with liquid crystal shutters. According to ISO 16673:2007 both methods are applicable. Therefore, the results and findings are compared and discussed for three use cases: Occlusion software application (display blanking) as a teaching aid, self-test for software developers and laboratory tests. For most tasks, both methods yield comparable results. Using display blanking for teaching purposes and propagating the method could be valuable. For the use in a typical developer workbench/desktop self-test, the operator must be aware that various influences can result in an underestimation of occlusion metrics. Nevertheless, it would be a benefit if developers apply the method in an early phase. For laboratory tests, we would further recommend the use of occlusion glasses.

Out-of-equilibrium evolution of kinetically constrained many-body quantum systems under purely dissipative dynamics.

We explore the relaxation dynamics of quantum many-body systems that undergo purely dissipative dynamics through non-classical jump operators that can establish quantum coherence. Our goal is to shed light on the differences in the relaxation dynamics that arise in comparison to systems evolving via classical rate equations. In particular, we focus on a scenario where both quantum and classical dissipative evolution lead to a stationary state with the same values of diagonal or "classical" observables. As a basis for illustrating our ideas we use spin systems whose dynamics becomes correlated and complex due to dynamical constraints, inspired by kinetically constrained models (KCMs) of classical glasses. We show that in the quantum case the relaxation can be orders of magnitude slower than the classical one due to the presence of quantum coherences. Aspects of these idealized quantum KCMs become manifest in a strongly interacting Rydberg gas under electromagnetically induced transparency (EIT) conditions in an appropriate limit. Beyond revealing a link between this Rydberg gas and the rather abstract dissipative KCMs of quantum glassy systems, our study sheds light on the limitations of the use of classical rate equations for capturing the non-equilibrium behavior of this many-body system.

The topological glass in ring polymers

We study the dynamics of concentrated, long, semi-flexible, unknotted and unlinked ring polymers embedded in a gel by Monte Carlo simulation of a coarse-grained model. This involves the ansatz that the rings compactify into a duplex structure where they can be modelled as linear polymers. The classical polymer glass transition involves a rapid loss of microscopic freedom within the polymer molecule as the temperature is reduced toward Tg. Here we are interested in temperatures well above Tg where the polymers retain high microscopic mobility. We analyse the slowing of stress relaxation originating from inter-ring penetrations (threadings). For long polymers an extended network of quasi-topological penetrations forms. The longest relaxation time appears to depend exponentially on the ring polymer contour length, reminiscent of the usual exponential slowing (e.g., with temperature) in classical glasses. Finally, we discuss how this represents a universality class for glassy dynamics.

New oxysulphide glasses in Sb 2S 3–M mO n and Sb 2S 3–Sb 2O 3–M mO n systems

New oxysulphide glasses involving antimony sulphide (Sb 2S 3), antimony oxide (Sb 2O 3) and M m O n (M = Cu +1, Pb +2, Sn +2, Zn +2, Ba +2, In +3, Bi +3 and V +5) have been investigated and characterized. They exhibit physical properties, different from those of classical oxide glasses and chalcogenide glasses. Glass-forming regions have been found in the Sb 2S 3–M m O n binary systems based on antimony sulphide as the main glass former and Sb 2S 3–Sb 2O 3–M m O n ternary systems derived from the Sb 2S 3–Sb 2O 3 binary glass. Most glasses are easy to prepare and quite stable in air. Depending on the composition and the nature of the M cation, glass transition temperature, T g, is between 190 and 290 °C, crystallization temperature, T c, is between 243 and 442 °C and the stability factor T c −T g is between 23 and 170 °C. Optical properties of these glasses have been measured. They generally appear black with no transparency in the visible range. For some thin glass samples, the infrared absorption edge extends up to about 12 μm.

Nonlinear Screening Theory of the Coulomb Glass

A nonlinear screening theory is formulated to study the problem of gap formation and its relation to glassy freezing in classical Coulomb glasses. We find that a pseudogap ("plasma dip") in a single-particle density of states begins to open already at temperatures comparable to the Coulomb energy. This phenomenon is shown to reflect the emergence of short-range correlations in a liquid (plasma) phase, a process which occurs even in the absence of disorder. Glassy ordering emerges when disorder is present, but this occurs only at temperatures roughly an order of magnitude lower. Our result demonstrate that the formation of the plasma dip at high temperatures is a process distinct from the formation of the Efros-Shklovskii pseudogap, which in our model emerges only within the glassy phase.