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<jats:title>Abstract</jats:title> <jats:p>Alternating twist (AT) multilayer graphene systems are at the heart of recent research efforts on flat band superconductivity and therefore precise descriptions of their atomic and electronic structures are desirable. We present the electronic structure of AAʹAAʹ… stacked AT <jats:italic>N</jats:italic>-layer (t<jats:italic>N</jats:italic>G) graphene for <jats:inline-formula> <jats:tex-math><?CDATA $N = $?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>N</mml:mi> <mml:mo>=</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tdmac8a00ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>3-10, 20 layers and bulk AT graphite systems where the atomic structure is relaxed using a molecular dynamics simulation code. The low energy bands depend sensitively on the relative sliding between the layers but we show explicitly up to N = 6 that the highly symmetric AA′AA′. . . stacking is energetically preferred among all interlayer sliding geometries of each added layer, justifying why experimental devices consistently show results compatible with this geometry. It is found that lattice relaxation enhances electron–hole asymmetry, and leads to small reductions of the magic angle values with respect to analytical or continuum model calculations with fixed tunneling strengths that we quantify from few layers to bulk AT-graphite. The twist angle error tolerance near the magic angles obtained by maximizing the density of states of the nearly flat bands expand progressively from 0.05<jats:sup>∘</jats:sup> for twisted bilayer graphene to up to 0.2<jats:sup>∘</jats:sup> for AT-graphite, hence allowing a greater twist angle flexibility in multilayers. We further comment on the role of perpendicular electric and magnetic fields in modifying the electronic structure of the system and how the decoupling of t<jats:italic>N</jats:italic>G multilayers bands allows mapping onto those of periodic AT-graphite’s at different <jats:italic>k</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> values.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>T<jats:italic> <jats:sub>x</jats:sub> </jats:italic> MXene is a promising active material for developing fiber-based devices due to its exceptional electrical conductivity and electrochemical capacitance. However, fabricating robust fibers with high MXene content remains challenging due to shortcomings such as low interfacial adhesion between sheets and shrinkage-induced sheet disorientation during processing, leading to diminished physical and electrochemical properties. Here, we demonstrate the fabrication of tough, conductive, and electrochemically active fibers through a sequential bridging strategy involving calcium cation (Ca<jats:sup>2+</jats:sup>) infiltration of cellulose nanocrystal (CNC)-bridged MXene, cross-linked and dried under tension. The resulting fibers exhibited a record toughness of ∼2.05 MJ m<jats:sup>−3</jats:sup> and retained high volumetric capacitance (∼985 F cm<jats:sup>−3</jats:sup>), attributed to the synergistic CNC bridging, Ca<jats:sup>2+</jats:sup> cross-linking, and tension application during fiber drying. These fibers also surpass the conductivity of their unaligned pristine MXene counterpart (∼8347 S cm<jats:sup>−1</jats:sup> vs ∼5078 S cm<jats:sup>−1</jats:sup>), ascribed to the tension-induced improvement in MXene alignment within these fibers, mitigating the undesirable effects of inserting an insulating CNC bridge. We anticipate that improving the toughness and conductivity of sequentially bridged MXene fibers will pave the way for the production of robust multifunctional MXene fibers, allowing their use in practical high-performance applications like wearable electronics and energy storage devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>MXenes have demonstrated substantial promise as photocatalysts and electrocatalysts for a variety of applications such as self-powered photoelectrochemical (PEC)-type photodetector, hydrogen evolution reaction (HER), and vapor sensing applications. However, their mechanism is still poorly figured out. Currently, Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>T<jats:italic> <jats:sub>x</jats:sub> </jats:italic> MXene suffers from low photoresponsivity, high overpotential, and low sensitivity in such important applications. In order to develop catalytic activity and performances of those devices, modifications must be made to the structure of MXenes to enhance the separation of photogenerated charges, rate of the H<jats:sup>+</jats:sup>/e<jats:sup>−</jats:sup> couplings, and surface-active sites. These manipulations of MXenes heavily depend on understanding the mechanism of devices, appropriate modification elements, and the method of modification. This study for the first time reveals a facile solid-state annealing strategy for doping semi-metallic selenium (Se) atoms on Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>T<jats:italic> <jats:sub>x</jats:sub> </jats:italic> MXene for self-powered PEC-type photodetector, HER, and vapor sensor applications. The suitable characteristics of Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>T<jats:italic> <jats:sub>x</jats:sub> </jats:italic> make it an appropriate substrate to accommodate Se atoms. The well-designed Se-doped Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub> heterojunction including some TiO<jats:sub>2</jats:sub> cuboids could exhibit unprecedented photoresponsivity (up to 90 mA W<jats:sup>−1</jats:sup>) and detectivity (up to 2.0 × 10<jats:sup>8</jats:sup> cm Hz<jats:sup>1/2</jats:sup> W<jats:sup>−1</jats:sup>) for 420 nm light, HER (−0.7 V at 10 mA cm<jats:sup>−2</jats:sup>), and gas sensitivity (Z′ = 347 Ω and Z′′ = 150 Ω, for ethanol) in comparison with the pristine Ti<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>T<jats:italic> <jats:sub>x</jats:sub> </jats:italic> nanosheets. The acquired promising results can be promoted with some other elements and also be examined in other electrolytes. Then, bring inspiration to the applications involving charge transfer, H<jats:sup>+</jats:sup>/e<jats:sup>−</jats:sup> couplings, and surface-active sites.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nonlinear anomalous (NLA) Hall effect is the Berry curvature dipole induced second-order Hall voltage or temperature difference induced by a longitudinal electric field or temperature gradient. These are the prominent Hall responses in time-reversal symmetric systems. These band-geometry induced responses in recently realized twistronic platforms can probe their novel electronic band structure and topology. Here, we investigate the family (electrical, thermoelectric, and thermal) of second-order NLA Hall effects in the moiré system of twisted double bilayer graphene (TDBG). We combine the semiclassical transport framework with the continuum model of TDBG to demonstrate that the NLA Hall signals can probe topological phase transitions in moiré systems. We show that the whole family of NLA Hall responses undergo a sign reversal across a topological phase transition. Our study establishes a deeper connection between valley topology and nonlinear Hall effects in time-reversal symmetric systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Silicene, the two-dimensional (2D) allotrope of silicon, is a promising material for electronics. So far, the most direct synthesis strategy has been to grow it epitaxially on metal surfaces; however, the effect of the strong silicon-metal interaction on the structure and electronic properties of the metal-supported silicene is generally poorly understood. In this work, we consider the <jats:inline-formula> <jats:tex-math><?CDATA $\left( {4 \times 4} \right)$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>4</mml:mn> <mml:mo>×</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tdmac8a01ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>-silicene monolayer (ML) grown on Ag(111), probably the most illustrious representative of the 2D silicon family, and show that our experimental results refute the common interpretation of this system as a simple buckled, honeycomb ML with a sharp interface to the Ag substrate. Instead, the presented analysis demonstrates the pervasive presence of a second silicon species, which we conclude to be a Si–Ag alloy stacked between the 2D silicene and the silver substrate and scaffolding the 2D silicene layer. These findings question the current structural understanding of the silicene/Ag(111) interface and may raise expectations of analogous alloy systems in the stabilization of other 2D materials grown epitaxially on metal surfaces.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Based on first-principles calculations and quantum transport simulations, we systematically investigate the possibility of using two-dimensional transition metal borides (MBenes) as electrodes for two-dimensional monolayer MoS<jats:sub>2</jats:sub> via interfacial interactions, band bending, vertical Schottky barrier, tunneling probability, and lateral Schottky barrier. The weak interaction between the functionalized MBenes and MoS<jats:sub>2</jats:sub> results in MoS<jats:sub>2</jats:sub> retaining its original intrinsic properties while significantly reducing the Fermi level pinning effect; this, is perfectly consistent with the revised Schottky–Mott model after considering charge redistribution. Combined with band calculations and device local projection density of states, MoS<jats:sub>2</jats:sub>/TiBO, MoS<jats:sub>2</jats:sub>/TiBF, and MoS<jats:sub>2</jats:sub>/MoBO, either with the vertical hole Schottky barrier or the lateral hole Schottky barrier, are negative, forming p-type ohmic contacts. Our work provides theoretical guidance for constructing high-performance nanodevices and MoS<jats:sub>2</jats:sub>-based logic circuits for large-scale integrated circuits. We demonstrate the outstanding potential of MBenes as electrodes for nanodevices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>MXene with expanding interlayer and tunable terminations emerge as promising candidates for metal ion storage. Herein, we develop a facile urea decomposition strategy to obtain ultrathin nitrogen-modified Ti3C2Tx with optimized terminations (N-UT-Ti3C2Tx) as anode for sodium/potassium ion storage. Experimental results have shown that NH3 molecules produced by urea pyrolysis could introduce two types of nitrogen modifications in Ti3C2, function substitution for –OH (FS) and surface absorption on –O (SA). During subsequent hydrothermal and heating processes, the nitrogen atoms in situ substitute the lattice carbon in Ti3C2 (LS). Further, the effects of these nitrogen modifications in Ti3C2 on diffusion kinetics of Na+ and K+ are investigated by first-principles calculations. The superior Na+ storage performances of the N-UT-Ti3C2Tx anode are the main attribute of the nitrogen modification of LS in Ti3C2, while the excellent K+ storage performances come from the synergistic effects of the nitrogen modifications of FS and LS in Ti3C2. This work emphasizes the effectiveness of surface engineering of nitrogen modifications and optimized terminations for improving the electrochemical performances of Ti3C2Tx and inspires the design of heteroatom modified MXenes for energy storage. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Novel 2D material CrI<jats:sub>3</jats:sub> reveals unique combination of 2D ferromagnetism and robust excitonic response. We demonstrate that the possibility of the formation of magnetic topological defects, such as Neel skyrmions, together with large excitonic Zeeman splitting, leads to giant scattering asymmetry, which is the necessary prerequisite for the excitonic anomalous Hall effect. In addition, the diamagnetic effect breaks the inversion symmetry, and in certain cases can result in exciton localization on the skyrmion. This enables the formation of magnetoexcitonic quantum dots with tunable parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Steering photogenerated electron flow to the effective reactive sites is ideal for photocatalytic H2 evolution. Herein, as a proof-of-concept, NiS is coupled with a typical Schottky heterojunction of Ti3C2Tx MXene@In2S3 through the photodepotition method towards improving the photocatalytic H2 evolution performance. In addition to the Schottky effect-mediated electron transfer in Ti3C2Tx MXene@In2S3 heterojunctions, p-n junctions form between In2S3 and NiS to extract photoinduced electrons, which is found to cooperate with the role of effective H2 evolution reactive sites. The synergistic dual functions of NiS cooporate with Ti3C2Tx MXene promote multichannel electron transfer in Ti3C2Tx MXene@In2S3-NiS hybrids to improve the photocatalytic hydrogen evolution reaction (HER) efficiency by 41 times compared to the bare In2S3. These results enlighten the engineering of the spatial transfer of photoinduced electrons to the reactive sites toward boosting the efficiency of photocatalytic HER. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Twisted bilayered graphenes at magic angles are systems housing long ranged periodicity of moir´e patterns together with short ranged periodicity associated with the individual graphenes. Such materials are a fertile ground for novel states largely driven by electronic correlations. Here we find that the ubiquitous Casimir force can serve as a platform for macroscopic manifestations of the quantum effects stemming from the magic angle bilayered graphenes properties and their phases determined by electronic correlations. By utilizing comprehensive calculations for the electronic and optical response, we find that Casimir torque can probe anisotropy from the Drude conductivities in nematic states, while repulsion in the Casimir force can help identify topologically nontrivial phases in magic angle twisted bilayered graphenes.</jats:p>