Symmetry Breaking Research Articles

Enhancing circular dichroism with anisotropic heterogeneous-structure based on MQBIC resonance

Metasurfaces based on quasi-bound states in the continuum (QBIC) typically require careful tuning of structural parameters to meet critical coupling condition, thereby maximizing circular dichroism (CD). In this study, we propose an innovative heterogeneous-structure comprising four pairs of symmetry-breaking silicon dielectric rods embedded in an anisotropic polymer. The resonance of magnetic QBIC (MQBIC) within the dielectric rods generates a CD response, while the polymer effectively modulates the chirality of the heterogeneous-structure and enhances the CD. This enhancement occurs because the resonance of the MQBIC in the diagonal direction of the heterogeneous-structure is confined, leading to a break in mirror symmetry. Further investigations reveal that even when critical coupling condition are not satisfied, CD can still be maximized through rotational modulation. Additionally, the critical coupling condition for the resonance of MQBIC in the heterogeneous-structure are more readily achievable, allowing the CD response to remain unconstrained by lattice constants. This research is anticipated to have a significant impact on the fields of biosensing and medical imaging in the future.

Symmetry Restoration and Quantum Mpemba Effect in Symmetric Random Circuits.

Entanglement asymmetry, which serves as a diagnostic tool for symmetry breaking and a proxy for thermalization, has recently been proposed and studied in the context of symmetry restoration for quantum many-body systems undergoing a quench. In this Letter, we investigate symmetry restoration in various symmetric random quantum circuits, particularly focusing on the U(1) symmetry case. In contrast to nonsymmetric random circuits where the U(1) symmetry of a small subsystem can always be restored at late times, we reveal that symmetry restoration can fail in U(1)-symmetric circuits for certain weak symmetry-broken initial states in finite-size systems. In the early-time dynamics, we observe an intriguing quantum Mpemba effect implying that symmetry is restored faster when the initial state is more asymmetric. Furthermore, we also investigate the entanglement asymmetry dynamics for SU(2) and Z_{2} symmetric circuits and identify the presence and absence of the quantum Mpemba effect for the corresponding symmetries, respectively. A unified understanding of these results is provided through the lens of quantum thermalization with conserved charges.

Topological valley waveguide state transport based on the nesting difference

Acoustic topological waveguide states are characterized by topologically protected transport. Existing acoustic topological valley-locked waveguide state transport structures can only realize single-scene acoustic field modulation due to the limitation of structural tunability, and it is difficult to realize width degree of freedom and reconfigurable transport paths of acoustic waves by adjusting the transport structure for complex acoustic field. Therefore, the transport structures become a conceptualized idea in terms of tunability. Our study introduces a nesting method in the design of the sonic crystal scatterer, which splits the scatterer structure into a removable outer shell and a core, and three topological phase transitions can be realized by only changing the nesting method of the sonic crystal shell, this approach constructs a fully reconfigurable topological waveguide. The results demonstrate that changing the nesting of the sonic crystals induces effective spatial inversion symmetry breaking, which leads to the valley topological phase transitionSimulations and experiments demonstrate that this transport structure has excellent robust transport properties with large inflection corners, and it is capable of realizing acoustic focusing, acoustic channeling, and acoustic logic gates. This fully reconfigurable sonic crystal design method can provide implications for the modulation of other classical waves.

Orbit symmetry breaking in MXene implements enhanced soft bioelectronic implants.

Bioelectronic implants featuring soft mechanics, excellent biocompatibility, and outstanding electrical performance hold promising potential to revolutionize implantable technology. These biomedical implants can record electrophysiological signals and execute direct therapeutic interventions within internal organs, offering transformative potential in the diagnosis, monitoring, and treatment of various pathological conditions. However, challenges remain in improving excessive impedance at the bioelectronic-tissue interface and thus the efficacy of electrophysiological signaling and intervention. Here, we devise orbit symmetry breaking in MXene (a low-cost scalability, biocompatible, and conductive two dimensionally layered material, which we refer to as OBXene), which exhibits low bioelectronic-tissue impedance, originating from the out-of-plane charge transfer. Furthermore, the Schottky-induced piezoelectricity stemming from the asymmetric orbital configuration of OBXene facilitates interlayered charge transport in the device. We report an OBXene-based cardiac patch applied on the left ventricular epicardium of both rodent and porcine models to enable spatiotemporal epicardium mapping and pacing while coupling the wireless and battery-free operation for long-term real-time recording and closed-loop stimulation.

Kitaev honeycomb antiferromagnet in a field: quantum phase diagram for general spin

We use tensor-network methods and high-order linked-cluster expansions to explore the quantum phase diagram of the antiferromagnetic Kitaev honeycomb model in a magnetic field for general spin S values. Tensor network calculations for the pure Kitaev model confirm the absence of fluxes and spin-spin correlations beyond nearest neighbors, while revealing discrete orientational symmetry breaking for S ∈ 1, 3/2, 2, consistent with the semiclassical limit. An intermediate region between Kitaev phases and the high-field polarized phase is identified for all considered spin values, showing a sequence of potential phases characterized by distinct local magnetization patterns while the total magnetization increases smoothly as a function of the field. Linked-cluster expansions for the high-field zero-momentum gap and spectral weight indicate a quantum critical breakdown of the polarized phase, suggesting exotic physics at intermediate Kitaev couplings.

Machine learning assisted screening of two dimensional chalcogenide ferromagnetic materials with Dzyaloshinskii Moriya interaction

Magnetic skyrmions are potential candidates for high-density storage and logic devices because of their inherent topological stability and nanoscale size. Two-dimensional (2D) Janus transition metal chalcogenides (TMDs) are widely used to induce skyrmions due to the breaking of inversion symmetry. However, the experimental synthesis of Janus TMDs is rare, which indicates that the Janus configuration might not be the most stable MXY structure. Here, through machine-learning-assisted high-throughput first-principles calculations, we demonstrate that not all MXY compounds can be stabilized in Janus layered structure and a large proportion prefer to form other configurations with lower energy than the Janus configuration. Interestingly, these new configurations exhibit a strong Dzyaloshinskii–Moriya interaction (DMI), which can generate and stabilize skyrmions even under a strong magnetic field. This work provides not only an efficient method for obtaining ferromagnetic materials with strong DMI but also a theoretical guidance for the synthesis of TMDs via experiments.

Durable Photo-Pyroelectric Detection in a Diamine-Constructed Lead-Free Hybrid Perovskite Ferroelectric.

As a subcategory of pyroelectric materials, hybrid perovskite ferroelectrics possess substantial pyroelectric properties and exceptional light absorption characteristics, demonstrating significant potential in the photo-pyroelectric (PPE) detection field. Despite the significant advantages of hybrid perovskite ferroelectric materials for PPE detection, both the lead issue and the weak stability from van der Waals interactions in monoamines have hindered their further application. Here, 1D lead-free ferroelectric (BDA)SbBr5 (1, where BDA is 1,4-butanediammonium) is fabricated to achieve PPE detection. Compound 1 exhibits significant symmetry breaking attributed to the order-disorder transition of organic cations and octahedral distortions. Specifically, compound 1 enables broad-spectrum PPE detection from UV to near-infrared (377-980nm) and further realizes switchable pyroelectric current after polarization. More importantly, the stability of the pyroelectric current is preserved without degradation over three months, attributed to the hydrogen bonding interactions of butanediamide. Further theoretical calculations of compound 1 reveal a more negative energy of formation than its monoamine homologs (BA)2SbBr5 (where BA is n-butylammonium), which is evidence of its stability. These findings highlight 1 as a promising candidate for high-stability and environmentally friendly PPE wide-spectrum detection, representing a noteworthy advancement in the ferroelectric field.

Constructing the Fulde-Ferrell-Larkin-Ovchinnikov State in a CrOCl/NbSe2 van der Waals Heterostructure.

Time reversal symmetry breaking in superconductors, resulting from external magnetic fields or spontaneous magnetization, often leads to unconventional superconducting properties. In this way, an intrinsic phenomenon called the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state may be realized by the Zeeman effect. Here, we construct the FFLO state in an artificial CrOCl/NbSe2 van der Waals (vdW) heterostructure by utilizing the superconducting proximity effect of NbSe2 flakes. The proximity-induced superconductivity demonstrates a considerably weak gap of about 0.12 meV, and the in-plane upper critical field reveals the behavior of the FFLO state. First-principles calculations uncover the origin of the proximitized superconductivity, which indicates the importance of Cr vacancies or line defects in CrOCl. Moreover, the FFLO state could be induced by the inherent large spin splitting in CrOCl. Our findings not only provide a practical scheme for constructing the FFLO state but also inspire the discovery of an exotic FFLO state in other two-dimensional vdW heterostructures.

Recording morphogen signals reveals mechanisms underlying gastruloid symmetry breaking.

Aggregates of stem cells can break symmetry and self-organize into embryo-like structures with complex morphologies and gene expression patterns. Mechanisms including reaction-diffusion Turing patterns and cell sorting have been proposed to explain symmetry breaking but distinguishing between these candidate mechanisms of self-organization requires identifying which early asymmetries evolve into subsequent tissue patterns and cell fates. Here we use synthetic 'signal-recording' gene circuits to trace the evolution of signalling patterns in gastruloids, three-dimensional stem cell aggregates that form an anterior-posterior axis and structures resembling the mammalian primitive streak and tailbud. We find that cell sorting rearranges patchy domains of Wnt activity into a single pole that defines the gastruloid anterior-posterior axis. We also trace the emergence of Wnt domains to earlier heterogeneity in Nodal activity even before Wnt activity is detectable. Our study defines a mechanism through which aggregates of stem cells can form a patterning axis even in the absence of external spatial cues.

Steering high-Q intrinsic chiral quasi-bound states in the continuum via engineered 2.5D phase-change metasurfaces.

High-Q intrinsic quasi-bound states in the continuum (QBICs) require three-dimensional (3D) geometries with both in-plane and out-of-plane mirror symmetry breakings, hindering practical implementations due to the complex architectures. Here we demonstrate that high-Q intrinsic QBICs can be flexibly controlled by using the engineered 2.5D phase-change metasurfaces of Ge2Sb2Te5 (GST). By introducing the additional out-of-plane perturbations of slant angle θ and azimuthal angle φ, highly efficient and high-Q intrinsic circular dichroism (CD) for both reflection and transmission can be realized. The spinning-selected magnetic dipole (MD) is responsible for the high-Q intrinsic chirality. The high-Q intrinsic CD is robust to the variation of structural parameters, and its Q-factor and resonance location can be tuned through the phase transition of GST.

Controlled light distribution with coupled microresonator chains via Kerr symmetry breaking

Within optical microresonators, the Kerr interaction of photons can lead to symmetry breaking of optical modes. In a ring resonator, this leads to the interesting effect that light preferably circulates in one direction or in one polarization state. Applications of this effect range from chip-integrated optical diodes to nonlinear polarization controllers and optical gyroscopes. In this work, we study Kerr-nonlinearity-induced symmetry breaking of light states in coupled resonator optical waveguides (CROWs). We discover, to our knowledge, a new type of controllable symmetry breaking that leads to emerging patterns of dark and bright resonators within the chains. Beyond stationary symmetry broken states, we observe Kerr-effect-induced homogeneous periodic oscillations, switching, and chaotic fluctuations of circulating powers in the resonators. Our findings are of interest for controlled multiplexing of light in photonic integrated circuits, neuromorphic computing, topological photonics, and soliton frequency combs in coupled resonators.

New 5-6-6-5 (fourfold) and 5-9-6 defect Configurations in g-SiC (graphene-like hexagonal monolayer silicon carbide)

Abstract Computational studies using the density functional theory (DFT) were employed to analyze defect configurations in g-SiC. The SiC supercells containing 72 atoms were used for simulation. We simulate C-vacancy (VC) and Si-vacancy (VSi). We relaxed all atoms so that the atomic force tolerance is 1.0 × 10−4 Ha/Bohr. The unrelaxed defective configurations have the same symmetry as the perfect configuration, which is a D3h symmetry. During relaxation, atoms neighboring the vacancy were displaced to reach a ground state condition. In the case of VC, a Si atom at the center of the defect has four bonds, resulting in a new 5-6-6-5 fourfold configuration with a C2v symmetry. In the case of VSi, a C atom forms bonds with two other C atoms, resulting in a new configuration, namely a 5-9-6 configuration. We identified that this configuration also has a C2v symmetry. Thus, symmetry breaking (lowering) occurs from D3h to C2v. We calculated the formation energy, which is 3.28 eV for the 5-6-6-5 fourfold and 3.92 eV for the 5-9-6 configuration. We also calculated the Density of States (DOS), and the results show that both configurations have semiconductor material properties suitable for promising optoelectronic devices with an infrared spectrum for future applications.

Nano and micro-structural complexity of nematic liquid crystal configurations

Of our interest are frustration-driven pattern generating mechanisms in systems which in bulk equilibrium display spatially homogeneous long-range orientational order in absence of perturbations. As testbed material, we select thermotropic nematic liquid crystals. In bulk, they exhibit weakly discontinuous order–disorder phase transformation on varying temperature where the ordered nematic phase features spatially uniform axial order along an arbitrary symmetry breaking direction. However, due to continuous symmetry breaking (CSB) the established order is extremely susceptible to various perturbations which are in real systems in general always present. We theoretically illustrate how diverse complex patterns could be excited. Particularly intriguing configurations could appear if topological defects are present that could be generated via CSB. Our analysis is based on a relatively simple Lebwohl-Lasher-type model in which we could get analytical insight into phenomena of our interest. Using it we illustrate history dependent early stage isotropic-nematic phase evolution and final patterns in presence of “impurities” (e.g., nanoparticles). We show how characteristic effective interaction characteristics predict qualitatively different emerging patterns. Our analysis is based on CSB which is ubiquitous in nature. Consequently, demonstrated mechanisms are expected to manifest also in other condensed matter systems whose ordered phase is formed via CSB. We illustrate how kinetics and impurities could impact key structural properties of the systems of our interest.

Mott Transitions: A Brief Review

AbstractThis short review provides an overview of some aspects of the current understanding of Mott insulators and Mott metal‐insulator transitions. The development of this field is traced, from earliest classical views to the state‐of‐the‐art picture based on methods of quantum field theory. A quasi‐local view point, characterizing “pure” Mott physics, throughout this article is focused on. Following an extensive discussion on Mott transitions in one‐ and multi‐orbital Hubbard models, progress is reviewed in first‐principles correlation‐based approaches in achieving a quantitative description of insulator‐metal transitions in two celebrated Mott materials. Building thereupon, success of such approaches in providing microscopic justification for the famed Mott criterion, as well as in the attempts to model emerging devices is reviewed briefly. The study is concluded with a discussion of a class of Mott insulators modeled by the Kugel‐Khomskii model, and discuss how progress in the understanding of novel quantum liquid‐crystal‐like order provides an attractive opportunity to gain insight into topologically ordered states and topological‐to‐trivial phase transitions for certain quantum spin models in terms of a dual description in terms of Landau‐like symmetry breaking.

Alpha sensing, NIR to green light emission in Er3+ doped PbWO4 nanoparticles with modification of calcination atmosphere

In this study, various concentrations (0.5, 1, and 1.5 at%) of Er3+ PbWO4 nanoparticles (PWO: Er NPs) were prepared using a co-precipitation procedure, and the effect of the calcination atmosphere (air and argon) on the luminescence properties and scintillation responses were investigated. Different characterization analyses were carried out to study the structural and optical characteristics of prepared samples. We found evidence of the transformation of the PWO Scheelite structure into a non-centered group, which effectively influences the symmetry properties of the structure and subsequently its luminescence and sensing properties. Both Ar atmosphere and Er concentration contribute to the distortion of the scheelite structure and the symmetry breaking. However, with increasing dopant concentrations, the lattice becomes more homogeneously distorted, causing the structure to re-symmetrize and, as a result, the intensity of luminescence increases, particularly magnetic dipolar (MD) transitions that correspond to NIR emission. The ideal conditions are given when the impurity percentage reaches 1.5 at%, in the Ar atmosphere. Our PWO: Er (1.5 at%-Ar) sample had a maximum count rate of 1388 and 2082 and detection efficiency of 0.216 and 0.170 cps/Bq under 241Am sources with 0.22 and 0.26 μc activities, respectively. By exceeding the efficiency of the commercial ZnS(Ag), it showed promising potential for practical applications in future optoelectronic domains.

Two Distinct Charge Orders in Infinite-Layer PrNiO2+δ Revealed by Resonant X-Ray Diffraction

Abstract Research of infinite-layer nickelates has unveiled a broken translation symmetry, which has sparked significant interest in its root, its relationship to superconductivity, and its comparison to charge order in cuprates. In this study, resonant x-ray scattering measurements were performed on thin films of infinite-layer PrNiO2+δ . The results show significant differences in the superlattice reflection at the Ni L 3 absorption edge compared to that at the Pr M 5 resonance in their dependence on energy, temperature, and local symmetry. These differences point to two distinct charge orders, although they share the same in-plane wavevectors. It is suggested that these dissimilarities could be linked to the excess oxygen dopants, given that the resonant reflections were observed in an incompletely reduced PrNiO2+δ film. Furthermore, azimuthal analysis indicates that the oxygen ligands likely play a crucial role in the charge modulation revealed at the Ni L 3 resonance.

Spontaneous symmetry breaking and vortices in a tri-core nonlinear fractional waveguide

We introduce a waveguiding system composed of three linearly-coupled fractional waveguides, with a triangular (prismatic) transverse structure. It may be realized as a tri-core nonlinear optical fiber with fractional group-velocity dispersion (GVD), or, possibly, as a system of coupled Gross–Pitaevskii equations for a set of three tunnel-coupled cigar-shaped traps filled by a Bose–Einstein condensate of particles moving by Lévy flights. The analysis is focused on the phenomenon of spontaneous symmetry breaking (SSB) between components of triple solitons, and the formation and stability of vortex modes. In the self-focusing regime, we identify symmetric and asymmetric soliton states, whose structure and stability are determined by the Lévy index of the fractional GVD, the inter-core coupling strength, and the total energy, which determines the system’s nonlinearity. Bifurcation diagrams (of the supercritical type) reveal regions where SSB occurs, identifying the respective symmetric and asymmetric ground-state soliton modes. In agreement with the general principle of the SSB theory, the solitons with broken inter-component symmetry prevail with the increase of the energy in the weakly-coupled system. Three-components vortex solitons (which do not feature SSB) are studied too. Because the fractional GVD breaks the system’s Galilean invariance, we also address mobility of the vortex solitons, by applying a boost to them.

Transport through a monolayer-tube junction: Sheet-to-tube spin current

We develop a method to calculate the electron flow between an arbitrary atomic monolayer sheet and an arbitrary tube by expressing the corresponding sheet-tube tunneling matrix elements with those between sheets. We use this method to calculate the spin current from a monolayer silicene sheet with sublattice-staggered current-induced spin polarization to a silicene tube. The calculated sheet-to-tube spin current exhibits an oscillation as a function of the tube circumferential length because the Fermi points in the tube cross the Fermi circle in the sheet. Furthermore, the spin current with spin in the out-of-plane direction, which is absent in the sheet-sheet junction (including twisted sheets) with C3 rotational symmetry, appears in an oscillating form in the tube-sheet junction due to the broken C3 rotational symmetry. This is an example of the symmetry manipulation which realizes switching a particular component of the spin current.

Chiral symmetry breaking, chiral partners, and the [formula omitted] and [formula omitted] in medium

We clarify the concept of chiral partners. For a vector meson, the isospin-zero and hypercharge-zero state in the flavor octet mixes with the flavor singlet state. Since the flavor singlet vector meson does not have a chiral partner, the mixed ω and ϕ mesons will not have chiral partners. This means that even when chiral symmetry is restored, these mesons will not become degenerate with their corresponding parity partners. On the other hand, the K1 and K∗ mesons are chiral partners, and both have widths smaller than 100 MeV. Therefore, we emphasize that studying these mesons in environments where chiral symmetry is restored is particularly important for understanding the effect of chiral symmetry restoration on chiral partners and their masses.

Real-space diffusion theory from quantum mechanics using analytic continuation

We show that a physical correspondence between Brownian motion and quantum mechanics can be established by formal analytic continuation if Wick rotation (t→it) is replaced by the mirror symmetric, complex conjugate time transformation t→±it. Invariance of the square modulus of the wave function under this transformation reveals a tight connection between Born's interpretation of the probability density and the proper time t2=(−it)(+it), as being both the result of a time symmetry breaking in the informational content of the microscopic (quantum) world, which takes place as we move to a macroscopic level. We find that under the transformation t→±it, the Schrödinger equation and its complex conjugate conforms with a stochastic-mechanical model of the Brownian motion of a particle. From the present analysis, Nelson's osmotic velocity arises naturally and the quantum phase function admits a classical interpretation in terms of a continuous (scalar) potential field that influences the motion of the particle. The maximum phase variation defines the direction of the osmotic and current velocity. Whereas the paper focuses on the correlation between quantum mechanics and Ficks's second law for a constant diffusion coefficient, a discussion is also provided on the possibility of a quantum mechanical formulation for anomalous diffusion, where the diffusion coefficient is a function of space and/or time.