Spontaneous Order Research Articles

Magnetic structures and spin reorientation in the B-site disordered perovskite PrFe0.5Cr0.5O3

Through the detailed studies utilizing x-ray and neutron powder diffraction and magnetometry measurements, we report the magnetic phase transitions in the B-site disorder perovskite oxide PrFe0.5Cr0.5O3. The Fe3+/Cr3+ sublattice was observed to form a long-range magnetic order with the GxFz configuration below TN = 270 K from neutron powder diffraction. It then undergoes the second-order phase transition to FxGz spin configuration below 210 K and the transition ends at ~170 K. On the other hand, long range magnetic ordering with FxCy configuration at Pr3+ sublattice can be identified at base temperature. The magnetic phase diagram is derived with spontaneous spin ordering and reorientation at A- and B-sublattices.

Chirality exists in the isotropic liquid above blue phase III

ABSTRACT The chirality of spherical liquid crystal droplets was investigated in this study. We report the effect of confinement on blue phase III (BPIII) spheres. We investigated the behaviours of the spherical BPIII droplets under the absence of surfactants or nanoparticles, spherical droplets in water, and polymerised capsules in air. Optical activity was observed between the transparent isotropic liquid phase and the bluish BPIII in the spherical BPIII droplets and capsules. This behaviour was not observed in the spherical cubic BP samples. Optical activities in the isotropic-phase temperature range were specific to BPIII. Furthermore, the phase transition behaviours of BPIII differed based on the sample confinement conditions, even for samples with the same mixture composition. Spherical confinement induced spontaneous microscopic chiral order formation at the isotropic liquid temperature range in the BPIII liquid crystal composition.

Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering

Odd-parity magnetic and magnetic toroidal multipoles in the absence of both spatial-inversion and time-reversal symmetries are sources of multiferroic and nonreciprocal optical phenomena. We investigate electronic states caused by an emergent odd-parity magnetic quadrupole (MQ) as a representative example of magnetic odd-parity multipoles. It is shown that spontaneous ordering of the MQ leads to an antisymmetric spin-orbital polarization in momentum space, which corresponds to a spin-orbital-momentum locking at each wave vector. By a symmetry argument, we show that the orbital or sublattice degree of freedom is indispensable to give rise to the spin-orbital-momentum locking. We demonstrate how the electronic band structures are modulated by the MQ ordering in the three-orbital system, in which the MQ is activated by the spin-dependent hybridization between the orbitals with different spatial parities. The spin-orbital-momentum locking is related to the microscopic origin of cross-correlated phenomena, e.g., the magnetic-field-induced symmetric and antisymmetric spin polarization in the band structure, the current-induced distortion, and the magnetoelectric effect. We also discuss similar spin-orbital-momentum locking in an antiferromagnet where the MQ degree of freedom is activated through the antiferromagnetic spin structure in a sublattice system.

Unconventional density waves and superconductivities in Fe-based superconductors and other strongly correlated electron systems

To seek high-$T_c$ pairing mechanism, many scientists have focused on the mysterious spontaneous rotational symmetry breaking above Tc, such as nematic order at $q=0$ and smectic order at $q\ne0$. Such exotic correlation-driven symmetry breaking in metals has become a central issue in condensed matter physics. We demonstrate the emergence of the nematic and smectic orders due to orbital polarization ($n_{xz}\ne n_{yz}$) and the symmetry breaking in the correlated intersite hopping (= bond order $\delta t_{i,j}$) in Fe-based and cuprate superconductors. In addition, we discuss exotic spontaneous loop current orders driven by the pure imaginary $\delta t_{i,j}$. These interesting ``unconventional density-waves'' originate from the quantum interference between different spin fluctuations that is described by the vertex correction (VC) in the field theory. In the next stage, we discuss electron-correlation driven superconductivity due to the fluctuations of unconventional density-waves. For this purpose, we suggest the beyond-Migdal-Eliashberg gap equation by including the VCs into the equation. In Fe-based superconductors, high-$T_c$ $s$-wave superconductivity can be mediated by nematic and smectic fluctuations because the pairing interaction is magnified by the VCs. We also discuss the multipolar fluctuation pairing mechanism in heavy fermion systems, owing to the cooperation between the strong spin-orbit interaction and the strong electron correlation. To summarize, we suggest that the quantum interference mechanism described by the VCs is the key ingredients to explain not only various unconventional density-waves, but also exotic superconducting states in many strongly correlated metals. We finally discuss some interesting future issues with respect to the quantum interference mechanism.

Design and demonstration of Al x In1−x P multiple quantum well light-emitting diodes

Direct bandgap Al x In1−x P alloys offer an advantage for red and amber light-emitting diode (LED) operation over conventional (Al x Ga1−x )0.5In0.5P alloys due to their higher direct bandgap energies. However, the coupled variation of its bandgap energy and lattice constant present challenges for fabricating quantum well (QW)-based LED devices on GaAs substrates. Here, we present the design and demonstration of Al x In1−x P red and amber LEDs incorporating multiple QW structures. Strain balancing the QW layers and manipulating the Al x In1−x P conduction band energy through control of spontaneous atomic ordering produce structures with higher energetic barriers to electron leakage compared to (Al x Ga1−x )0.5In0.5P LEDs. We also discuss future improvements that must be made to realize high efficiency red and amber LEDs.

Role of matrix phase and electric field gradient in Na1/2Bi1/2TiO3[sbnd]BaTiO3:ZnO composites

Na1/2Bi1/2TiO3-based materials exhibit potential for applications in high-power ultrasonics. The composites of Na1/2Bi1/2TiO3-yBaTiO3 (NBTyBT; y denotes mole%) with ZnO inclusions were demonstrated to stabilize a ferroelectric equilibrium that led to enhanced thermal depolarization temperature (Td) and increased mechanical quality factor (Qm). This work addresses the influence of the matrix NBTyBT phase by investigating two limiting choices based on symmetry (tetragonal/rhombohedral) and polar (relaxor/ferroelectric) nature. While the composites constituting the tetragonal NBT9BT (non-ergodic relaxor at room temperature) matrix phase exhibit improved Td, the critical temperatures in the composites with rhombohedral NBT3BT (displaying spontaneous ferroelectric order at room temperature) exhibit only marginal changes. Further, NBT3BT composites feature a 45% increase in Qm, while the corresponding increase is roughly three-fold for the NBT9BT composites. A 3-D Finite Element Method is used to simulate the electric field gradient at the matrix/inclusion interface, with the effective field distribution estimated to be higher than the applied field for highly conducting ZnO inclusions. The electrical properties indicate that, while the deviatoric stress at the matrix/inclusion interface stabilizes the ferroelectric equilibrium for the relaxor matrix phase, the stresses disrupt the long-range order for the ferroelectric matrix phase. These results establish the volume-limit of the second phase to stabilize a ferroelectric equilibrium, in addition to substantiating the role of residual stress evidenced by changes in the polar nature. Finally, a comparison of the composites with different NBTyBT phases is presented, with NBT6BT:ZnO composites demonstrating an optimal increase in both Td and Qm.

Crafting a Confucian Culture in Chinese Corporations: A Case Study of Guangzhou Borche

Corporate culture is an important source of enterprise’s soft power. Confucianism, which has been regarded as official teaching over a thousand years, manifests its profound values in modern management and is adopted by a number of private companies in China. This paper employs a case study method, concentrating on the development of Borche - a private enterprise in Guangzhou. Data and other information were collected from interviews, open reports and historical records and got ensured by triangulation verification. It seeks to explain how the Confucianism got internalized as part of a corporate culture and serves us its management guideline. The result demonstrates that the internalization of Confucian values in a corporation will go through three stages: cultural identity, identity strengthening and spontaneous order. Confucianism’s corporate culture is reflected in four aspects: of spirit, institution, behavior, and matter. The cultural infiltration mechanism is thus created. Keywords: corporate culture, Confucianism, cultural internalization mechanism, culture evolution

Self-Organization in Cold Atoms Mediated by Diffractive Coupling

This article discusses self-organization in cold atoms via light-mediated interactions induced by feedback from a single retro-reflecting mirror. Diffractive dephasing between the pump beam and the spontaneous sidebands selects the lattice period. Spontaneous breaking of the rotational and translational symmetry occur in the 2D plane transverse to the pump. We elucidate how diffractive ripples couple sites on the self-induced atomic lattice. The nonlinear phase shift of the atomic cloud imprinted onto the optical beam is the parameter determining coupling strength. The interaction can be tailored to operate either on external degrees of freedom leading to atomic crystallization for thermal atoms and supersolids for a quantum degenerate gas, or on internal degrees of freedom like populations of the excited state or Zeeman sublevels. Using the light polarization degrees of freedom on the Poincaré sphere (helicity and polarization direction), specific irreducible tensor components of the atomic Zeeman states can be coupled leading to spontaneous magnetic ordering of states of dipolar and quadrupolar nature. The requirements for critical interaction strength are compared for the different situations. Connections and extensions to longitudinally pumped cavities, counterpropagating beam schemes and the CARL instability are discussed.

Study of disorder in pulsed laser deposited double perovskite oxides by first-principle structure prediction

Double perovskite oxides, with generalized formula A2BB^{prime}O6, attract wide interest due to their multiferroic and charge transfer properties. They offer a wide range of potential applications such as spintronics and electrically tunable devices. However, great practical limitations are encountered, since a spontaneous order of the B-site cations is notoriously hard to achieve. In this joint experimental-theoretical work, we focused on the characterization of double perovskites La2TiFeO6 and La2VCuO6 films grown by pulsed laser deposition and interpretation of the observed B-site disorder and partial charge transfer between the B-site ions. A random structure sampling method was used to show that several phases compete due to their corresponding configurational entropy. In order to capture a representative picture of the most relevant competing microstates in realistic experimental conditions, this search included the potential formation of non-stoichiometric phases as well, which could also be directly related to the observed partial charge transfer. We optimized the information encapsulated in the potential energy landscape, captured via structure sampling, by evaluating both enthalpic and entropic terms. These terms were employed as a metric for the competition of different phases. This approach, applied herein specifically to La2TiFeO6, highlights the presence of highly entropic phases above the ground state which can explain the disorder observed frequently in the broader class of double perovskite oxides.

The concept of social liberalism of Frederick August von Hayek

According to some criteria, social liberalism is considered to be one of the types of liberalism. These studies are a reflection on Frederick August von Hayek’s concept of social liberalism, who is a supporter of political and economic freedom, but above all, individual freedom. This analysis aims to present the leading ideas of his social philosophy in the area of the function of the state, democracy, freedom, spontaneous order of individualism and equality.

Orbital-order phase transition in Pr1−xCaxMnO3 probed by photovoltaics

The phase diagram of $Pr_{1-x}Ca_xMnO_3$ is modified x $\le$ 0.3, which suggests a reevaluation of the phase diagram of other manganites in that doping region. Rather than an orbital ordered phase reaching up to high temperatures of approximately 800-1100 K, we propose a loss of spontaneous orbital order already near room temperature. Above this temperature, the phase is characterized by a finite orbital polarization and octahedral tilt pattern. The tilt pattern couples to the Jahn-Teller distortion and thus induces a remaining orbital order, which persists up to high temperatures, where the tilt order is lost as well. This explains the experimental observation of orbital order up to high temperatures. The reevaluation of the orbital order transition is based on observed anomalies of various physical properties at a temperatures of 220-260 K in epitaxial thin films of $Pr_{1-x}Ca_xMnO_3$ x=0.1, i.e.in the photovoltaic effect, electric transport, magnetization, optical and ultrafast transient pump probe studies. Finite-temperature simulations based on a tight-binding model with carefully adjusted parameters from first-principles calculations exhibit an orbital order phase transition at $T_{OO} \approx$ 300 K for x=0.1. This is consistent with the experimental observation of a temperature dependent change in lattice parameter for bulk samples of the same doping at 300 K for x=0.1 and 350 K for x=0, typical for a second order phase transition. Since our reassignment of the orbital order phase transition towards lower temperatures challenges a well-established and long-accepted picture, we provide results of multiple complementary measurements as well as a detailed discussion.

Digitization and the evolution of money as a social technology of account

Throughout the history of monetary thought, economists have predominantly emphasised the function of money as a medium of exchange along with the intrinsic properties that enhance its salability and credibility as the most liquid store of value. But the social institution of money co-evolves with technology. It is significant that the advent of digital crypto-currencies was initiated by computer scientists and has taken economists completely by surprise. As a consequence, it also forces our profession to rethink the basic phenomenology of money. In accordance with the views of Wieser and Schumpeter, digitization brings to the fore the immaterial function of money as a standard of value and social technology of account, which increasingly absorbs its function as a medium of exchange. The potential impact of this on economic policy is huge. The variety of different crypto coins has proven the technical feasibility of competing private currencies as proposed by Hayek. In the long term, however, there is reason to doubt the persistence of intense competition. One must fear that major digital platforms will extend their current dominance in multisided virtual market places to include digital payments and money. Central banks are increasingly anxious to preserve public sovereignty over the common unit of account and are considering issuing their own digital fiat money. After the current era of intense creative experimentation, the potentially new spontaneous order of private crypto-currencies is likely to be supplanted by central bank digital currencies (CBDCs), the design of which will depend on deliberate public choices and policies.

Non-local dxy nematicity and the missing electron pocket in FeSe

The origin of spontaneous electronic nematic ordering provides important information for understanding iron-based superconductors. Here, we analyze a scenario where the dxy orbital strongly contributes to nematic ordering in FeSe. We show that the addition of dxy nematicity to a pure dxz/dyz order provides a natural explanation for the unusual Fermi surface and correctly reproduces the strongly anisotropic momentum dependence of the superconducting gap. We predict a Lifshitz transition of an electron pocket mediated by temperature and sulfur doping, whose signatures we discuss by analysing available experimental data. We present the variation of momentum dependence of the superconducting gap upon suppression of nematicity. Our quantitatively accurate model yields the transition from tetragonal to nematic FeSe and the FeSe1−xSx series, and puts strong constraints on possible nematic mechanisms.

Anomalous fractional quantization in the kagomelike Heisenberg ladder: Emergence of the effective spin-1 chain

We study a Kagome-like spin-$1/2$ Heisenberg ladder with competing ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. Using the density-matrix renormalization group based calculations, we obtain the ground state phase diagram as a function of the ratio between the FM and AFM exchange interactions. Five different phases exist. Three of them are spin polarized phases; an FM phase and two kinds of ferrimagnetic (FR) phases (referred to as FR1 and FR2 phases). The spontaneous magnetization per site is $m=1/2$, $1/3$, and $1/6$ in the FM, FR1, and FR2 phases, respectively. This can be understood from the fact that an effective spin-1 Heisenberg chain formed by the upper and lower leg spins has a three-step fractional quantization of the magnetization per site as $m=1$, $1/2$, and $0$. In particular, an anomalous "intermediate" state $m=1/2$ of the effective spin-1 chain with the reduced Hilbert space of a spin from $3$ to $2$ dimensional is highly unexpected in the context of conventional spin-1 physics. Thus, surprisingly, the effective spin-1 chain behaves like a spin-1/2 chain with SU(2) symmetry. The remaining two phases are spin-singlet phases with translational symmetry breaking in the presence of valence bond formations. One of them is octamer-siglet phase with a spontaneous octamerization long-range order of the system, and the other is period-4 phase characterized by the magnetic superstructure with a period of four structural unit cells. In these spin-singlet phases, we find the coexistence of valence bond structure and gapless chain. Although this may be emerged through the order-by-disorder mechanism, there can be few examples of such a coexistence.

Can We Design Spontaneity? The Tension between Evolution and Design and the Defense of Liberalism in Hayek

F.A Hayek is one of the most important and influential advocates of liberalism in the 20th century. His theory is famously based on the concept of spontaneous order, an order emerging from the interaction of individuals without central control and appears critical of every form of interventionism. At the same time Hayek also defends the necessity to improve or even to constitute a liberal order. This seminal tension, between an evolutionary strand and a designing strand in Hayek's political theory, gave birth to a set of debates regarding the consistency of Hayek's thinking. In this article I argue, against several commentators and critics, that the theory of spontaneous order, which draws on complexity theory and cultural evolution, does not clash with Hayek's defense of liberalism, but allow for a better understanding of it. My analysis puts forward the importance of a liberal design of a framework enhancing spontaneity, a radical liberalism, which goes beyond a whiggish liberalism defending the slow piecemeal evolution of social norm and institutions. I thus defend that Hayek provides a theory of a liberal design of spontaneity. Since Hayek is concerned by the liberal framework allowing for the growth of a beneficial spontaneous order, his liberalism should not be defended on evolutionary grounds, which are flawed, but on normative grounds, which are debatable.

Design and growth of InAsP metamorphic buffers for InGaAs thermophotovoltaic cells

The structural and optical properties of InAsxP1-x metamorphic buffers grown by metal–organic chemical vapor deposition on InP (100) substrates have been investigated. High-resolution X-ray reciprocal space mapping around the (115) InP lattice point reveals that the strain relaxations of the InAsxP1-x with x = 0.5, 0.55, and 0.7 are 98%, 92%, and 96%, while the lateral correlation lengths are 17, 62, and 28 nm, respectively. The optical bandgap energy of the InAsP derived from photoreflectance (PR) measurements decreases from 0.819 to 0.621 eV at 300 K when increasing As composition from x = 0.5 to 0.7. The bowing parameter for the optical bandgap of the InAsP is increased with increasing As composition, which is attributable to the increased spontaneous CuPt-type ordering in InAsP. It is found from the excitation power-dependent PR measurement that the InAsxP1-x layers have different degrees of the bandgap redshift due to the reduced thermal conductivity caused by crystal imperfections generated during the strain relaxation process.

Emergence of charge loop current in the geometrically frustrated Hubbard model: A functional renormalization group study

Spontaneous current orders due to odd-parity order parameters attract increasing attention in various strongly correlated metals. Here, we discover a novel spin-fluctuation-driven charge loop current (cLC) mechanism based on the functional renormalization group (fRG) theory. The present mechanism leads to the ferro-cLC order in a simple frustrated chain Hubbard model. The cLC appears between the antiferromagnetic and $d$-wave superconducting ($d$SC) phases. While the microscopic origin of the cLC has a close similarity to that of the $d$SC, the cLC transition temperature $T_{\rm cLC}$ can be higher than the $d$SC one for wide parameter range. Furthermore, we reveal that the ferro cLC order is driven by the strong enhancement of the forward scatterings $g_2$ and $g_4$ owing to the two dimensionality based on the $g$-ology language. The present study indicates that the cLC can emerge in metals near the magnetic criticality with geometrical frustration

Development of ferroelectric nematic fluids with giant-ε dielectricity and nonlinear optical properties.

Superhigh-ε materials that exhibit exceptionally high dielectric permittivity are recognized as potential candidates for a wide range of next-generation photonic and electronic devices. In general, achieving a high-ε state requires low material symmetry, as most known high-ε materials are symmetry-broken crystals. There are few reports on fluidic high-ε dielectrics. Here, we demonstrate how small molecules with high polarity, enabled by rational molecular design and machine learning analyses, enable the development of superhigh-ε fluid materials (dielectric permittivity, ε > 104) with strong second harmonic generation and macroscopic spontaneous polar ordering. The polar structures are confirmed to be identical for all the synthesized materials. Furthermore, adapting this strategy to high-molecular weight systems allows us to generalize this approach to polar polymeric materials, creating polar soft matters with spontaneous symmetry breaking.

Weakening of Solvation-Induced Ordering by Composition Fluctuation in Salt-Doped Block Polymers.

The spontaneous ordering of block polymers doped with ions is affected by both selective solvation and long-range Coulombic interaction. The mean-field treatment was recently shown to overestimate the solvation-induced ordering, requiring a large solvation radius to fit experimental phase diagrams, which may be relieved by including composition fluctuations. Treating the composition fluctuations in such systems is challenging because of the need of resolving heterogeneous dielectric profile that couples with the ordering itself. Starting from a minimal model, we develop a Landau-Brazovskiĭ expansion for the free energy of salt-doped block polymer near the ordering transition. It is found that the wavelength for typical composition fluctuations first decreases with salt doping, due to Coulombic interaction, then increases due to ionic solvation. Two mechanisms that weaken the solvation-enhanced ordering are identified: the Brazovskiĭ-type composition fluctuation that stabilizes disordered phase, and the coupling between mismatch in dispersion interaction and the dielectric permittivity through monomeric polarizability.

Dynamic behavior of elevators under random inflow of passengers.

Elevators can be regarded as oscillators driven by the calls of passengers who arrive randomly. We study the dynamic behavior of elevators during the down peak period numerically and analytically. We assume that new passengers arrive at each floor according to a Poisson process and call the elevators to go down to the ground floor. We numerically examine how the round-trip time of a single elevator depends on the inflow rate of passengers at each floor and reproduce it by a self-consistent equation considering the combination of floors where the call occurs. By setting an order parameter, we show that the synchronization of two elevators occurs irrespective of final destination (whether the elevators did or did not go to the top floor). It indicates that the spontaneous ordering of elevators emerges from the Poisson noise. We also reproduce the round-trip time of two elevators by a self-consistent equation considering the interaction through the existence of passengers and the absence of volume exclusion. Those results suggest that such interaction stabilizes and characterizes the spontaneous ordering of elevators.