Disordered hyperuniformity in two-dimensional amorphous silica

Abstract

Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength density fluctuations and are endowed with unique novel physical properties. Here we report the first discovery of disordered hyperuniformity in atomic-scale 2D materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscope images. Subsequent simulations suggest that the observed DHU is closely related to the strong topological and geometrical constraints induced by the local chemical order in the system. Moreover, we show via large-scale density functional theory calculations that DHU leads to almost complete closure of the electronic band gap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.Disorder hyperuniform (DHU) systems are a unique class of disordered systems which suppress large-scale density fluctuations like crystals and yet possess no Bragg peaks [1, 2]. For a point configuration (e.g., a collection of particle centers of a many-body system), hyperuniformity is manifested as the vanishing structure factor in the infinite-wavelength (or zero-wavenumber) limit, i.e., lim k→0 S(k) = 0, where k = 2π/λ is the wavenumber. In this case of a random field, the hyperuniform condition is given by lim k→0ψ (k) = 0, whereψ(k) is the spectral density [2]. It has been suggested that hyperuniformity can be considered as a new state of matter [1], which possesses a hidden order in between of that of a perfect crystal and a totally disordered system (e.g. a Poisson distribution of points).Recently, a wide spectrum of physical and biological systems have been identified to possess the remarkable property of hyperuniformity, which include the density fluctuations in early universe [3], disordered jammed packing of hard particles [4][5][6][7], certain exotic classical ground states of many-particle systems [8][9][10][11][12][13][14][15], jammed colloidal systems [16][17][18][19], driven non-equilibrium systems [20][21][22][23], certain quantum ground states [24,25], avian photoreceptor patterns [26], organization of adapted im- * These authors contributed equally to this work. † correspondence sent to: xwxfat@gmail.com ‡ correspondence sent to: mohanchen@pku.edu.cn § correspondence sent to: yang.jiao.2@asu.edu ¶ correspondence sent to: hzhuang7@asu.edu mune systems [27], amorphous silicon [28, 29], a wide class of disordered cellular materials [30], dynamic random organizating systems [31-35], and even the distribution of primes on the number axis [36]. In addition, it has been shown that hyperuniform materials can be designed to possess superior physical properties including ...

Stone–Wales defects preserve hyperuniformity in amorphous two-dimensional networks

“…Subsequent detailed transmission electron microscopy characterization indicates that its structure is distinctly different from the random network model (51), a widely accepted structural model of amorphous 2D materials. Moreover, a recent study of amorphous 2D silica reveals that the distribution of silicon atoms possesses the remarkable property of DHU (45). In a wider context, amorphous carbon-based systems have been extensively studied, including graphene sheets (54)(55)(56), cross-linked graphene network (57), and amorphous glassy carbon and carbon fibers (58,59), to name a few.…”

“…Very recently, DHU patterns of electrons emerging from a quantum jamming transition of correlated many-electron state in two-dimensional (2D) materials, which leads to enhanced electronic transport, have been observed (44). In addition, it is found that DHU distribution of localized electrons in 2D amorphous silica results in an insulator-to-metal transition in the material (45). These exciting discoveries not only suggest the existence of a novel DHU state of electrons in low-dimensional materials but also shed light on novel device applications by exploring the unique emergent properties of the DHU electron states.…”

Impact of particle size and multiple scattering on the propagation of waves in stealthy-hyperuniform media

“…Recently, a new state of matter has been discovered that is characterized by cancellation of normalized density fluctuations at infinite wavelength. This state is called hyperuniformity (or superhomogeneity) [14,15] and lead to very particular and interesting properties that have already been observed at natural mesoscopic [16] or microscopic scales [17]. Self assembly of dense packings can also be hyperuniform [18,19].…”

Circular swimming motility and disordered hyperuniform state in an algae system

“…voratum cells self-organize into disordered hyperuniform states with suppressed density fluctuations at large length scales. Hyperuniformity (43,44) has been considered as a new form of material order which leads to novel functionalities (45)(46)(47)(48)(49); it has been observed in many systems, including avian photoreceptor patterns (50), amorphous ices (51), amorphous silica (52), ultracold atoms (53), soft matter systems (54)(55)(56)(57)(58)(59)(60)(61), and stochastic models (62)(63)(64). Our work demonstrates the existence of hyperuniformity in active matter and shows that hydrodynamic interactions can be used to construct hyperuniform states.…”