Skew trapezoidal bipyramidal distortion in MoS6 unit stabilizing distorted phases of 1T-MoS2 single layer

The exceptional electrocatalytic performance of the 1T phase of MoS2 in the hydrogen evolution reaction has motivated researchers to design methods for enhancing the stability of this phase. Herein, the electronic origin of the stability of 1T-MoS2 and its distorted phases: 1T' (zig-zag), 1T′′ (diamond chain), and 1T′′′ (triangle) was elucidated using first-principles calculations. The phase stability can be altered by the repeating MoS6 units that play a significant role in the generation of metal clusters. A novel skew trapezoidal bipyriamidal (STB) distortion was observed in the MoS6 unit, which increased the stability of the distorted 1T phases in MoS2. The highly distorted STB unit was found in the stable 1T' phase with an enhanced dyz orbital population. The short edges of the distorted STB increase the electron density fraction of the Mo atoms, promoting Mo-Mo bond formation. The 1T' phase exhibited superior stability due to stronger electron delocalization in the Mo-Mo bond compared to that in the 1T′′ and 1T′′′ phases. The nature of Mo-Mo bonding varied on different metal clusters for 1T' (σ, π, and δ), 1T′′ (π and σ), and 1T′′′ (σ) bond types. Therefore, the stability of the 1T'-MoS2 phase depends on the extent of distortion in the MoS6 unit, Mo-Mo bond nature, and layer thickness.11Nsciescopu

Activated somatostatin interneurons orchestrate memory microcircuits

Despite recent advancements in identifying engram cells, our understanding of their regulatory and functional mechanisms remains in its infancy. To provide mechanistic insight into engram cell functioning, we introduced a novel local microcircuit labeling technique that enables the labeling of intraregional synaptic connections. Utilizing this approach, we discovered a unique population of somatostatin (SOM) interneurons in the mouse basolateral amygdala (BLA). These neurons are activated during fear memory formation and exhibit a preference for forming synapses with excitatory engram neurons. Post-activation, these SOM neurons displayed varying excitability based on fear memory retrieval. Furthermore, when we modulated these SOM neurons chemogenetically, we observed changes in the expression of fear-related behaviors, both in a fear-associated context and in a novel setting. Our findings suggest that these activated SOM interneurons play a pivotal role in modulating engram cell activity. They influence the expression of fear-related behaviors through a mechanism that is dependent on memory cues. © 2023 Elsevier Inc.11Nsciescopu

Limit of Bergman kernels on a tower of coverings of compact Kähler manifolds

We prove the convergence of the Bergman kernels and the L2-Hodge numbers on a tower of Galois coverings { Xj} of a compact Kähler manifold X converging to an infinite Galois (not necessarily universal) covering X~. We also show that, as an application, sections of canonical line bundle KXj for sufficiently large j give rise to an immersion into some projective space, if so do sections of KX~. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.11Nsciescopu

Random-singlet-like state emergent in s = 5/2 frustrated cubic lattice

We employ thermodynamic and electron spin resonance (ESR) techniques to elucidate the effects of quenched disorder on a ground state of s= 5 / 2 frustrated cubic antiferromagnet La 3 Sb 3 Mn 2 O 14 . We observe the development of multiple ESR lines for temperatures below 80 K. Concomitantly, the ESR linewidth exhibits a power-law increase, accompanied by an intriguing shift in resonance fields. These observations point to the occurrence of inhomogeneous magnetism. Additionally, ac magnetic susceptibility and magnetization data obey a scaling relation of χ′(H, T) and M(H, T) in μBH/ kBT with the scaling exponent α= 0.53 . This scaling behavior alludes to the formation of a random-singlet-like state and the presence of abundant low-lying excitations. Our results highlight the concerted interplay of strong disorder and frustration to stabilize a putative random-singlet state even in classical and high-dimensional spin systems. © 2024, The Korean Physical Society.11Nscopuskc

Rational Molecular Design of Redox-Active Carbonyl-Bridged Heterotriangulenes for High-Performance Lithium-Ion Batteries

Carbonyl aromatic compounds are promising cathode candidates for lithium-ion batteries (LIBs) because of their low weight and absence of cobalt and other metals, but they face constraints of limited redox-potential and low stability compared to traditional inorganic cathode materials. Herein, by means of first-principles calculations, a significant improvement of the electrochemical performance for carbonyl-bridged heterotriangulenes (CBHTs) is reported by introducing pyridinic N in their skeletons. Different center atoms (B, N, and P) and different types of functionalization with nitrogen effectively regulate the redox activity, conductivity, and solubility of CBHTs by influencing their electron affinity, energy levels of frontier orbitals and molecular polarity. By incorporating pyridinic N adjacent to the carbonyl groups, the electrochemical performance of N-functionalized CBHTs is significantly improved. Foremost, the estimated energy density reaches 1524 Wh kg−1 for carbonyl-bridged tri (3,5-pyrimidyl) borane, 50% higher than in the inorganic reference material LiCoO2, rendering N-functionalized CBHTs promising organic cathode materials for LIBs. The investigation reveals the underlying structure-performance relationship of conjugated carbonyl compounds and sheds new lights for the rational design of redox-active organic molecules for high-performance lithium ion batteries (LIBs).11Nsciescopu

Quantum spin nematic phase in a square-lattice iridate

Spin nematic is a magnetic analogue of classical liquid crystals, a fourth state of matter exhibiting characteristics of both liquid and solid 1,2. Particularly intriguing is a valence-bond spin nematic 3–5, in which spins are quantum entangled to form a multipolar order without breaking time-reversal symmetry, but its unambiguous experimental realization remains elusive. Here we establish a spin nematic phase in the square-lattice iridate Sr2IrO4, which approximately realizes a pseudospin one-half Heisenberg antiferromagnet in the strong spin–orbit coupling limit 6–9. Upon cooling, the transition into the spin nematic phase at T C ≈ 263 K is marked by a divergence in the static spin quadrupole susceptibility extracted from our Raman spectra and concomitant emergence of a collective mode associated with the spontaneous breaking of rotational symmetries. The quadrupolar order persists in the antiferromagnetic phase below T N ≈ 230 K and becomes directly observable through its interference with the antiferromagnetic order in resonant X-ray diffraction, which allows us to uniquely determine its spatial structure. Further, we find using resonant inelastic X-ray scattering a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state 10,11. Taken together, our results reveal a quantum order underlying the Néel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity 12,13. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.11Nsciescopu

On a rainbow extremal problem for color-critical graphs

Given (Formula presented.) graphs (Formula presented.) over a common vertex set of size (Formula presented.), what is the maximum value of (Formula presented.) having no “colorful” copy of (Formula presented.), that is, a copy of (Formula presented.) containing at most one edge from each (Formula presented.) ? Keevash, Saks, Sudakov, and Verstraëte denoted this number as (Formula presented.) and completely determined (Formula presented.) for large (Formula presented.). In fact, they showed that, depending on the value of (Formula presented.), one of the two natural constructions is always the extremal construction. Moreover, they conjectured that the same holds for every color-critical graphs, and proved it for 3-color-critical graphs. They also asked to classify the graphs (Formula presented.) that have only these two extremal constructions. We prove their conjecture for 4-color-critical graphs and for almost all (Formula presented.) -color-critical graphs when (Formula presented.). Moreover, we show that for every non-color-critical non-bipartite graphs, none of the two natural constructions is extremal for certain values of (Formula presented.). © 2023 Wiley Periodicals LLC.11Nsciescopu

Measuring Nonlocal Brane Order with Error-Corrected Quantum Gas Microscopes

Exotic quantum many-body states, such as Haldane and spin liquid phases, can exhibit remarkable features like fractional excitations and non-Abelian statistics and offer new understandings of quantum entanglement in many-body quantum systems. These phases are classified by nonlocal correlators that can be directly measured in atomic analog quantum simulating platforms, such as optical lattices and Rydberg atom arrays. However, characterizing these phases in large systems is experimentally challenging because they are sensitive to local errors like atom loss, which suppress its signals exponentially. Additionally, protocols for systematically identifying and mitigating uncorrelated errors in analog quantum simulators are lacking. Here, we address these challenges by developing an error-correction method for large-scale neutral atom quantum simulators using optical lattices. Our error-correction method can distinguish correlated particle-hole pairs from uncorrelated holes in the Mott insulator. After removing the uncorrelated errors, we observe a dramatic improvement in the nonlocal parity correlator and find the perimeter scaling law. Furthermore, the error model provides a statistical estimation of fluctuations in site occupation, from which we measure the generalized brane correlator and confirm that it can be an order parameter for Mott insulators in two dimensions. Our work provides a promising avenue for investigating and characterizing exotic phases of matters in large-scale quantum simulators. © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.11Nscopu

The ergodicity question when imaging DNA conformation using liquid cell electron microscopy

Assessing the ergodicity of graphene liquid cell electron microscope measurements, we report that loop states of circular DNA interconvert reversibly and that loop numbers follow the Boltzmann distribution expected for this molecule in bulk solution, provided that the electron dose is low (80-keV electron energy and electron dose rate 1-20 e- Å-2 s-1). This imaging technique appears to act as a slow motion camera that reveals equilibrated distributions by imaging the time average of a few molecules without the need to image a spatial ensemble.11Nscopu

Prime vertex-minors of a prime graph

A graph is prime if it does not admit a partition (A,B) of its vertex set such that min{|A|,|B|}≥2 and the rank of the A×B submatrix of its adjacency matrix is at most 1. A vertex v of a graph is non-essential if at least two of the three kinds of vertex-minor reductions at v result in prime graphs. In 1994, Allys proved that every prime graph with at least four vertices has a non-essential vertex unless it is locally equivalent to a cycle graph. We prove that every prime graph with at least four vertices has at least two non-essential vertices unless it is locally equivalent to a cycle graph. As a corollary, we show that for a prime graph G with at least six vertices and a vertex x, there is a vertex v≠x such that G∖v or G∗v∖v is prime, unless x is adjacent to all other vertices and G is isomorphic to a particular graph on odd number of vertices. Furthermore, we show that a prime graph with at least four vertices has at least three non-essential vertices, unless it is locally equivalent to a graph consisting of at least two internally-disjoint paths between two fixed distinct vertices having no common neighbors. We also prove analogous results for pivot-minors. © 2023 Elsevier Ltd11Nsciescopu