Exotic Structures Research Articles

Bubbles structure & droplet of glycerol forming system of lenses with tunable focal length

One of the most exotic structure in liquid crystal is the cholesteric structure. Due to their periodic helical structure, cholesteric liquid crystals (CLCs) promising candidates for a myriad of different photonic applications. CLCs can exhibit bubbles domain, defects arranged in two dimensions, which have been used as an array of micro-lenses with electrically tunable focal length. The focal length of the micro-lenses is limited in micro-meter scale, moreover each micro-lens has it is own focal point. The purpose of this work is how to construct a system of lenses with just one electrically tunable focal length. The system is formed by the bubble domain (micro-lens) accompanied by additional droplet of glycerol (big-lens). Hence, by tuning the focal length of the micro-lenses, the focal length of the system can be varied. This work covers the methodology that was used for making the bubbles domain based on CLCs

Exotic Mazur manifolds and knot trace invariants

From a handle-theoretic perspective, the simplest contractible 4-manifolds, other than the 4-ball, are Mazur manifolds. We produce the first pairs of Mazur manifolds that are homeomorphic but not diffeomorphic. Our diffeomorphism obstruction comes from our proof that the knot Floer homology concordance invariant ν is an invariant of the trace of a knot K⊂S3, i.e. the smooth 4-manifold obtained by attaching a 2-handle to B4 along K. This provides a computable, integer-valued diffeomorphism invariant that is effective at distinguishing exotic smooth structures on knot traces and other simple 4-manifolds, including when other adjunction-type obstructions are ineffective. We also show that the concordance invariants τ and ϵ are not knot trace invariants. As a corollary to the existence of exotic Mazur manifolds, we produce integer homology 3-spheres admitting two distinct S1×S2 surgeries, resolving a question from Problem 1.16 in Kirby's list [28].

Symplectic 4-manifolds on the Noether line and between the Noether and half Noether lines

We construct simply connected, minimal, symplectic 4-manifolds with exotic smooth structures and each with one Seiberg–Witten basic class up to sign, on the Noether line and between the Noether and half Noether lines by star surgeries introduced by Karakurt and Starkston, and by using complex singularities. We also construct certain configurations of complex singularities in the rational elliptic surfaces geometrically, without using any monodromy arguments. By using these configurations, we give symplectic embeddings of star shaped plumbings inside (some blow-ups of) elliptic surfaces.

Dynamic covalent self-assembly of mechanically interlocked molecules solely made from peptides.

Mechanically interlocked molecules (MIMs), such as rotaxanes and catenanes, have captured the attention of chemists both from a synthetic perspective and because of their role as simple prototypes of molecular machines. Although examples exist in nature, most synthetic MIMs are made from artificial building blocks and assembled in organic solvents. Synthesis of MIMs from natural biomolecules remains highly challenging. Here we report on a synthesis strategy for interlocked molecules solely made from peptides—mechanically interlocked peptides (MIPs). Fully peptidic, cysteine-decorated building blocks were self-assembled in water to generate disulfide-bonded dynamic combinatorial libraries consisting of multiple different rotaxanes, catenanes and daisy chains as well as more exotic structures. Detailed NMR spectroscopy and mass spectrometry characterization of a [2]catenane comprised of two peptide macrocycles revealed that this structure has rich conformational dynamics reminiscent of protein folding. Thus, MIPs can serve as a bridge between fully synthetic MIMs and those found in nature.

Hierarchical self-assembly of polydisperse colloidal bananas into a two-dimensional vortex phase

Self-assembly of microscopic building blocks into highly ordered and functional structures is ubiquitous in nature and found at all length scales. Hierarchical structures formed by colloidal building blocks are typically assembled from monodisperse particles interacting via engineered directional interactions. Here, we show that polydisperse colloidal bananas self-assemble into a complex and hierarchical quasi-two-dimensional structure, called the vortex phase, only due to excluded volume interactions and polydispersity in the particle curvature. Using confocal microscopy, we uncover the remarkable formation mechanism of the vortex phase and characterize its exotic structure and dynamics at the single-particle level. These results demonstrate that hierarchical self-assembly of complex materials can be solely driven by entropy and shape polydispersity of the constituting particles.

Optical, electrical, and catalytic (photo-and sono-) properties of indium doped γ-Bi2O3 with Sillenite structure

The exotic structure and properties exhibited by the metastable solids are exemplified adequately in the materials chemistry area. In this report, metastable γ-Bi2O3 has been stabilized without adding any impurity by the auto-combustion method and compared with the changes in structure and optical property brought out by the inclusion of In3+ ions. Compositions doped with indium (7 and 10 mol% in place of bismuth) resulted in stoichiometric Sillenite-type structures as revealed by their powder X-ray diffraction patterns, FTIR, and Raman spectral measurements. The pale yellow γ-Bi2O3 acquired pale brown coloration on indium inclusion, and the intensities varied with varying indium content. Optical bandgap reduction from 2.63 (pure γ-Bi2O3) to 2.41 eV occurred when 10 mol% of indium was doped in place of bismuth. The formation of non-stoichiometric Sillenite structures was noticed in samples with higher indium concentrations (up to 50 mol%). The non-stoichiometric samples displayed intense brown color and showed a drastic reduction in the optical bandgap, reaching values as low as 1.57 eV (50 mol% indium doped sample). From XPS analysis and red-ox titrations, nearly 5% of oxygen excess was estimated for the non-stoichiometric samples doped with indium. The BET surface area of indium doped non-stoichiometric Sillenites (126 m2/g) was higher than indium doped stoichiometric Sillenites (74 m2/g). The oxygen ion conductivity studies of pure γ-Bi2O3 and indium doped non-stoichiometric Sillenites revealed a marginal rise in conductivity with indium inclusion.

Distinct chemical fixation of CO2 enabled by exotic gold nanoclusters

Atomically precise metal nanoclusters, especially the metal nanoclusters with an exotic core structure, have given rise to a great deal of interest in catalysis, attributing to their well-defined structures at the atomic level and consequently unique electronic properties. Herein, the catalytic performances of three gold nanoclusters, such as Au38S2(S-Adm)20 with a body-centered cubic (bcc) kernel structure, Au30(S-Adm)18 with a hexagonal close-packed (hcp) core structure, and Au21(S-Adm)15 with a face-centered cubic (fcc) kernel structure, were attempted for the CO2 cycloaddition with epoxides toward cyclic carbonates. Due to the excess positive charge with a strong Lewis acidity and large chemical adsorption capacity, the bcc-Au38S2(S-Adm)20 nanocluster outperformed the hcp-Au30(S-Adm)18 and fcc-Au21(S-Adm)15 nanoclusters. Additionally, the synergistic effect between the gold nanocluster and co-catalyst played a crucial role in CO2 cycloaddition.

Pressure-Induced Electronic and Structural Transition in Nodal-Line Semimetal ZrSiSe.

The nodal-line semimetals have recently gained attention as a promising material due to their exotic electronic structure and properties. Here, we investigated the structural evolution and physical properties of nodal-line semimetal ZrSiSe under pressure via experiments and theoretical calculations. An isostructural electronic transition is observed at ∼6 GPa. Upon further compression, the original tetragonal phase starts to transform into an orthorhombic phase at ∼13 GPa and the two phases coexist until the maximal experimental pressure. By analysis of the electronic band structure, we suggest that the significant changes in the Fermi surface contribute to the occurrence of the isostructural electronic transition. The results provide a new insight into the structure and properties of ZrSiSe.

Symmetry-enforced band nodes in 230 space groups

Crystallographic symmetries enforcing band touchings (BTs) in the Brillouin zone (BZ) have been utilized to classify and predict the topological semimetals. Though the early proposed topological semimetals contain isolated nodal points in the BZ, the proposed nodal line semimetals later could host various structures of several nodal lines/loops: nodal chains, nodal nets or Hopf-links, etc. In this work, using compatibility relations, we first list all possible high symmetry lines (HSLs) that can be nodal lines itself, high symmetry planes (HSPLs) that can host nodal loops, high symmetry planes (HSPLs) that are nodal surfaces for all 230 SGs, with spin-orbit coupling and time-reversal symmetry considered or not. We then show how to diagnose a nodal loop from the band crossing in an HSL, or nodal line/surface from irreducible representation (irrep) of an high-symmetry point (HSP), while the rest cases correspond to nodal points. Among our results, those essential cases, for which the nodal points/lines/loops/surfaces must exist, are highlighted since they are promising for the realizations of (nearly) ideal nodal point/line/loop/surface semimetals, as well as systems with flexible tunability owning fixed structure of topological nodal points/lines/loops/surfaces. Based on our results, SGs allowing Hopf-link structure with one straight nodal line threading a nodal loop, or two nesting nodal loops lying in two respective high symmetry planes, are highlighted, with the predicted materials being B$_5$Pb$_2$IO$_9$ in SG 34 and SrAl$_2$Au$_3$ in SG 62, respectively. Our exhaustive results could serve as a useful guide for efficiently predicting and designing materials or artificial systems owning exotic geometric nodal structures of energy bands simply based on structure symmetries.

Self-Assembly of Isostatic Self-Dual Colloidal Crystals.

Self-dual structures whose dual counterparts are themselves possess unique hidden symmetry, beyond the description of classical spatial symmetry groups. Here we propose a strategy based on a nematic monolayer of attractive half-cylindrical colloids to self-assemble these exotic structures. This system can be seen as a 2D system of semidisks. By using MonteCarlo simulations, we discover two isostatic self-dual crystals, i.e., an unreported crystal with pmg space-group symmetry and the twisted kagome crystal. For the pmg crystal approaching the critical point, we find the double degeneracy of the full phononic spectrum at the self-dual point and the merging of two tilted Weyl nodes into one critically tilted Dirac node. The latter is "accidentally" located on the high-symmetry line. The formation of this unconventional Dirac node is due to the emergence of the critical flatbands at the self-dual point, which are linear combinations of "finite-frequency" floppy modes. These modes can be understood as mechanically coupled self-dual rhombus chains vibrating in some unique uncoupled ways. Our work paves the way for designing and fabricating self-dual materials with exotic mechanical or phononic properties.

Novel evidence for the σ-bond linear-chain molecular structure in 14C * *Supported by the National Key research and development Program of China (2018YFA0404403), the National Natural Science Foundation of China (11875074, 11875073, 12027809, 11635015, 11961141003) and the Continuous Basic Scientific Research Project (WDJC-2019-13)

A multi-nucleon transfer and cluster decay experiment, Li( B, C + Be) , is conducted at an incident beam energy of 55 MeV. This reaction channel has a significantly large Q-value, which favors populating the high lying resonant states in C. The decay paths, from these resonances to various states of the final nucleus Be, can be selected, owing to the experimentally achieved optimal resolution of the Q-value spectrum. A number of resonant states are reconstructed from the forward emitting Be + fragments, and their major molecular structures can be detected according to the selective decay paths and relative decay widths. A state at 22.4(2) MeV validates the previously measured and theoretically predicted band head of the positive-parity -bond linear-chain molecular band. Two additional resonances at 22.9(2) and 24.2(2) MeV are identified and consistent with the predicted and members of the same molecular band, thus providing novel evidences for the existence of the exotic clustering chain structure in neutron-rich carbon isotopes. A few high energy resonances, which also indicate the presence of the -bond molecular structure, are observed; however, further studies are still required to clarify their ascription in band systematics.

Floquet engineering ultracold polar molecules to simulate topological insulators

We present a quantitative, near-term experimental blueprint for the quantum simulation of topological insulators using lattice-trapped ultracold polar molecules. In particular, we focus on the so-called Hopf insulator, which represents a three-dimensional topological state of matter existing outside the conventional tenfold way and crystalline-symmetry-based classifications of topological insulators. Its topology is protected by a linking number invariant, which necessitates long-range spin-orbit-coupled hoppings for its realization. While these ingredients have so far precluded its realization in solid-state systems and other quantum simulation architectures, in an accompanying Letter [T. Schuster et al., Phys. Rev. Lett. 127, 015301 (2021)], we predict that Hopf insulators can arise naturally from the dipolar interaction. Here, we investigate a specific polar molecule architecture, where the effective ``spin'' is formed from sublattice degrees of freedom. We introduce two techniques that allow one to optimize dipolar Hopf insulators with large band gaps, and which should also be readily applicable to the simulation of other exotic band structures. First, we describe the use of Floquet engineering to control the range and functional form of dipolar hoppings and, second, we demonstrate that molecular AC polarizabilities (under circularly polarized light) can be used to precisely tune the resonance condition between different rotational states. To verify that this latter technique is amenable to current-generation experiments, we calculate, from first principles, the AC polarizability for ${\ensuremath{\sigma}}^{+}$ light for $^{40}\mathrm{K}^{87}\mathrm{Rb}$. Finally, we show that experiments are capable of detecting the unconventional topology of the Hopf insulator by varying the termination of the lattice at its edges, which gives rise to three distinct classes of edge mode spectra.

Epitaxial fabrication of AgTe monolayer on Ag(111) and the sequential growth of Te film

Transition-metal chalcogenides (TMCs) materials have attracted increasing interest both for fundamental research and industrial applications. Among all these materials, two-dimensional (2D) compounds with honeycomb-like structure possess exotic electronic structures. Here, we report a systematic study of TMC monolayer AgTe fabricated by direct depositing Te on the surface of Ag(111) and annealing. Few intrinsic defects are observed and studied by scanning tunneling microscopy, indicating that there are two kinds of AgTe domains and they can form gliding twin-boundary. Then, the monolayer AgTe can serve as the template for the following growth of Te film. Meanwhile, some Te atoms are observed in the form of chains on the top of the bottom Te film. Our findings in this work might provide insightful guide for the epitaxial growth of 2D materials for study of novel physical properties and for future quantum devices.

Topological Insulating Phase in Single-Layer Pentagonal Covalent Organic Frameworks: A Reticular Design Using Metal Phthalocyanine

Organic topological insulators have received tremendous attention lately due to their designability and highly chemical diversity. In this work, we propose an isoreticular series of single-layer π-conjugated covalent organic frameworks with the Cairo pentagonal tiling, termed mcm-ZnPc-1, mcm-ZnPc-2, mcm-ZnPc-3, and mcm-ZnPc-3N, where mcm is the crystal net’s symbol and ZnPc stands for zinc phthalocyanine. First-principles calculations using density functional theory show that mcm-ZnPc-1 and mcm-ZnPc-2 are trivial insulators with band gaps of 0.96 and 1.18 eV, respectively. Interestingly, expanding the π-conjugated system of mcm-ZnPc-2, followed by a chemical substitution, results in mcm-ZnPc-3 and mcm-ZnPc-3N with a distorted Dirac point and a quadratic band-crossing point in their band structures, respectively. The topological analyses indicate that mcm-ZnPc-3N is a Z2 topological insulator with a nontrivial gapless edge state. Our tight-binding model for the pentagonal lattice suggests that the topologically trivial-to-nontrivial transition can be attributed to the sufficient electronic coupling between two adjacent linkers and to the fact that the band-crossing point locates at the Fermi level. Remarkably, we show that replacing Zn in mcm-ZnPc-3N with Cd and Hg can substantially enlarge the nontrivial band gap from 0.3 meV up to 10 meV due to strong spin–orbit coupling strengths although a biaxial strain is necessary to tune the Fermi level of mcm-HgPc-3N in order to enter its topological insulating phase. Our proposed materials are predicted to be dynamically, thermally, and mechanically stable, thus paving the way for their experimental realization. This work not only introduces the pentagonal lattice as a building motif for framework structures but also demonstrates a strategy to engineer the exotic band structure of organic materials.

About the exotic structure of Zcs

Very recently a new hadronic structure around 3.98 GeV was observed in BESIII experiment. From its decay modes, it is reasonable for people to assign it to the category of exotic state, say Zcs+, the stranged-parter of Zc(3900). This finding indicates for the first time the tetraquark with strange quark in hidden-charm sector, and hence has a peculiar importance. By virtue of the QCD Sum Rule technique, we analyze the Zcs+ about its possible configuration and physical properties, and find it could be configured as a mixture of two types of structures, [1c]c¯u⊗[1c]s¯c and [1c]c¯c⊗[1c]s¯u, or [3c]c¯u⊗[3¯c]s¯c and [3c]c¯c⊗[3¯c]s¯u, with JP=1+. Physically, it then appears to be the emergence of a compound of four possible currents in each configuration, which tells that the single current evaluation of hadron spectroscopy and their decay properties are sometimes not enough. We find that in both cases the energy spectra may fit well with the experimental observation within the uncertainties, i.e. 3.98 GeV, while be noted that the molecular state is not favored by vector-meson-exchange model. Various Zcs+(3980) decay modes are evaluated, which are critical for pinning down its configuration and left for experimental verification. We also predict the mass of Zcs0, the neutral partner of Zcs+(3980), and analyze its dominant decay probabilities.

Space fabric wrinkles: history of observational searches for exotic structures in the Universe

The paper consistently presents the history and methodology of observational searches for cosmic strings of various nature. Cosmic strings are one-dimensional extended objects predicted by modern cosmology, which, however, have not yet been detected with a high degree of confidence. The presence of cosmic strings changes the global geometry of the Universe and could serve as a unique proof of higher-dimensional theories. The properties and features of these cosmological objects from the point of view of observational astronomy are discussed. The presentation is preceded by a brief mathematical theory of cosmic strings.

Exotic toroidal and superdeformed configurations in light atomic nuclei: Predictions using a mean-field Hamiltonian without parametric correlations

Mean-field calculations in multidimensional deformation spaces are performed and the shape coexistence and isomers generated by exotic nuclear configurations and toroidal and superdeformed ones are addressed. We use a phenomenological mean-field Hamiltonian of Woods-Saxon type with its universal parametrization involving eight parameters fixed once for all for the full periodic table. Original parametric correlations existing in this type of Hamiltonians are removed using methods of inverse problem theory of applied mathematics. Stochastic analysis of uncertainties of the final nuclear energy predictions with the obtained correlation-free parametrization is performed and the viability tests are illustrated and discussed. Prediction capacities of resulting model related to the description of the nuclear shape properties are cross-checked using the experimental information available, revealing full coherence. Presented results encourage experimental verification of predicted exotic structures; suggestions related to identification possibilities are formulated and discussed.

Customized depolarization spatial patterns with dynamic retardance functions

In this work we demonstrate customized depolarization spatial patterns by imaging a dynamical time-dependent pixelated retarder. A proof-of-concept of the proposed method is presented, where a liquid–crystal spatial light modulator is used as a spatial retarder that emulates a controlled spatially variant depolarizing sample by addressing a time-dependent phase pattern. We apply an imaging Mueller polarimetric system based on a polarization camera to verify the effective depolarization effect. Experimental validation is provided by temporal integration on the detection system. The effective depolarizance results are fully described within a simple graphical approach which agrees with standard Mueller matrix decomposition methods. The potential of the method is discussed by means of three practical cases, which include non-reported depolarization spatial patterns, including exotic structures as a spirally shaped depolarization pattern.

On some torus knot groups and submonoids of the braid groups

The submonoid of the 3-strand braid group B3 generated by σ1 and σ1σ2 is known to yield an exotic Garside structure on B3. We introduce and study an infinite family (Mn)n≥1 of Garside monoids generalizing this exotic Garside structure, i.e., such that M2 is isomorphic to the above monoid. The corresponding Garside group G(Mn) is isomorphic to the (n,n+1)-torus knot group–which is isomorphic to B3 for n=2 and to the braid group of the exceptional complex reflection group G12 for n=3. This yields a new Garside structure on (n,n+1)-torus knot groups, which already admit several distinct Garside structures.The (n,n+1)-torus knot group is an extension of Bn+1, and the Garside monoid Mn surjects onto the submonoid Σn of Bn+1 generated by σ1,σ1σ2,…,σ1σ2⋯σn, which is not a Garside monoid when n>2. Using a new presentation of Bn+1 that is similar to the presentation of G(Mn), we nevertheless check that Σn is an Ore monoid with group of fractions isomorphic to Bn+1, and give a conjectural presentation of it, similar to the defining presentation of Mn. This partially answers a question of Dehornoy–Digne–Godelle–Krammer–Michel.

Capping and gate control of anomalous Hall effect and hump structure in ultra-thin SrRuO3 films

Ferromagnetism and exotic topological structures in SrRuO3 (SRO) induce sign-changing anomalous Hall effect (AHE). Recently, hump structures have been reported in the Hall resistivity of SRO thin films, especially in the ultra-thin regime. We investigate the AHE and hump structure in the Hall resistivity of SRO ultra-thin films with an SrTiO3 (STO) capping layer and ionic liquid gating. STO capping results in sign changes in the AHE and modulation of the hump structure. In particular, the hump structure in the Hall resistivity is strongly modulated and even vanishes in STO-capped 4 unit cell films. In addition, the conductivity of STO-capped SRO ultra-thin films is greatly enhanced with restored ferromagnetism. We also performed ionic liquid gating to modulate the electric field at SRO/STO interface. Drastic changes in the AHE and hump structure are observed with different gate voltages. Our study shows that the hump structure as well as the AHE can be controlled by tuning inversion symmetry and the electric field at the interface.