We conducted a comprehensive analysis of the magnetic and electronic transport properties of the layered chalcogenide ${\mathrm{Cr}}_{1+\delta }{\mathrm{Te}}_2$ in its single-crystalline form. This material exhibits a ferromagnetic transition at a critical temperature of $T_C=191\mathrm{K}$, characterized by significant thermal hysteresis in the magnetization data below this temperature. Measurements of isothermal magnetization, magnetocaloric effect, and magnetoresistance indicate that the system exhibits strong magnetocrystalline anisotropy, with the $c$ axis serving as the easy axis of magnetization. The ${\mathrm{Cr}}_{1+\delta }{\mathrm{Te}}_2$ compound shows a pronounced anomalous Hall effect (AHE); however, existing experimental and theoretical data do not provide a clear understanding of the nature and origin of this phenomenon. Our experimental findings suggest that the skew scattering mechanism primarily accounts for the observed AHE. In contrast, our theoretical study reveals the presence of gapped nodal points accompanied by nonzero Berry curvature, which are expected to contribute towards intrinsic AHE. A detailed analysis of the electronic band structure, obtained by density functional theory calculations, reveals that the Berry curvature at different nodal points exhibits both positive and negative signs. These opposing contributions largely cancel each other out, thereby significantly diminishing the intrinsic contribution to the AHE.

The effect of structure relaxation on the potential energy surface (PES) of the interlayer interaction of twisted graphene bilayer is studied for a set of commensurate moiré systems using the registry-dependent empirical potential of Kolmogorov and Crespi. It is found that the influence of structure relaxation on the amplitude of PES corrugations (determining static friction) depends on the unit cell size (or related twist angle) of the moiré system. For moiré systems with the smallest unit cells, the amplitudes of PES corrugations calculated with and without account of structure relaxation are approximately the same. However, for large unit cell sizes, the structure relaxation can lead to an increase of PES corrugations by orders of magnitude. This means that structure relaxation can provide the main contribution to the static friction of a superlubric system under certain conditions (such as the contact size and twist angle). Moreover, the change of the PES type because of structure relaxation from a trigonal lattice of maxima to a trigonal lattice of minima is observed for systems with the moiré patterns (5,1) and (5,3). Based on the results obtained, possible crossovers between static friction modes taking place upon changing the twist angle in a macroscopic superlubric system consisting of identical layers are discussed. Additionally, it is shown that the PES for relaxed structures can still be approximated by the first Fourier harmonics compatible with symmetries of twisted layers analogously to the PES for rigid layers.

We present a first-principles study of $\mathrm{MnAlGe}/{\mathrm{TiO}}_2$ (001) heterostructure, where the interface between layered topological ferromagnetic MnAlGe and anatase ${\mathrm{TiO}}_2$ induces significant spintronic effects via proximity coupling. In the ferromagnetic bulk ground state, MnAlGe exhibits nontrivial topological properties in both its electronic and phononic bands. Upon interfacing with ${\mathrm{TiO}}_2$, electrons are transferred from MnAlGe, driving ${\mathrm{TiO}}_2$ from semiconducting to a metallic state, due to its proximity to the metallic MnAlGe layer. The resulting Ohmic contact induces nontrivial topological characteristics at the interface. Through quantum transport analysis within the framework of density functional theory and nonequilibrium Green's function method (DFT-NEGF), including current-voltage (I-V) and transmission spectrum computations, we demonstrate a notable spin injection efficiency of 43% at a bias voltage of 0.2 V in a $\mathrm{MnAlGe}/{\mathrm{TiO}}_2$ device, underscoring the efficient spin polarization facilitated by the proximity effect. Our findings reveal the potential of $\mathrm{MnAlGe}/{\mathrm{TiO}}_2$ heterostructure in advancing spintronic device performance, with the ability to finely tune spin injection and transport through deliberate interface engineering. This study provides critical insights into the synergistic role of topological and proximity effects, laying the groundwork for future innovations in spin-based electronics.

We have developed a first-principles method to calculate the electron-phonon coupling for specific modes and $\mathit{q}$ points in the Brillouin zone for crystalline organic semiconductors. Using the obtained coupling strengths, we propose an approach to compute the temperature-dependent mobilities of electrons and holes.

To validate our treatment of the electronic structures and vibrational properties, we calculate the Raman spectra in the lattice-phonon region and compare them with experimental data. We then compare the computed mobilities with available data for single crystals of naphthalene, anthracene, and tetracene (bulk polymorph), finding good agreement within the experimental range, especially when accounting for possible charged impurities. Finally, we discuss the observed differences between tetracene polymorphs.

Two-dimensional (2D) semiconductors are likely to dominate next-generation electronics due to their advantages in compactness and low power consumption. However, challenges such as high contact resistance and inefficient doping hinder their applicability. Here, we investigate work-function-mediated charge transfer (modulation doping) as a pathway for achieving high-performance p-type 2D transistors. Focusing on type-III band alignment, we explore the doping capabilities of 27 candidate materials, including transition metal oxides, oxyhalides, and $\alpha \text{−}{\mathrm{RuCl}}_3$, on channel materials such as transition metal dichalcogenides (TMDs) and group-III nitrides. Our extensive first-principles density functional theory (DFT) reveal p-type doping capabilities of high electron affinity materials, including $\alpha \text{−}{\mathrm{RuCl}}_3$, ${\mathrm{MoO}}_3$, and ${\mathrm{V}}_2{\mathrm{O}}_5$. We predict significant reductions in contact resistance and enhanced channel mobility through efficient hole transfer without introducing detrimental defects. We analyze transistor geometries and identify promising material combinations beyond the current focus on ${\mathrm{WSe}}_2$ doping, suggesting new avenues for hBN, AlN, GaN, and ${\mathrm{MoS}}_2$. This comprehensive investigation provides a roadmap for developing high-performance p-type monolayer transistors toward the realization of 2D electronics.

We successfully fabricated overdoped $\mathrm{T}{\mathrm{l}}_2\mathrm{B}{\mathrm{a}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ superconducting films with ozone annealing and obtained the systematic evolution of electrical transport properties with the ionic-liquid gating technique. It was found that superconducting transition temperature $T_{\mathrm{c}}$ varies in a dome shape as a function of doping, and the strange-metal phase exists where the doping level $p$ is beyond 0.19, in line with the reported phase diagrams of hole-doped cuprate superconductors. Moreover, the $T$-linear resistivity coefficient $A_1$ and $T_{\mathrm{c}}$ satisfy a quantitative scaling relation $T_{\mathrm{c}}\sim A_1^{0.5}$, which has been observed in various unconventional superconductors. This result further proves the universality of such a quantitative scaling, which points to an intrinsic link between superconducting pairing and strange metal scattering in high temperature superconductors. Our observations provide new insights toward finding a unified understanding of high-temperature superconductivity.

We report the impact of magnetic impurity substitution on the quantum disordered magnetic ground state of ${\mathrm{NaRuO}}_2$. Local $S=5/2$ moments are introduced into the frustrated triangular lattice of $J_{\text{eff}}=1/2$ Ru moments via Fe substitution in ${\mathrm{NaFe}}_x{\mathrm{Ru}}_{1-x}{\mathrm{O}}_2$, and the evolution of the magnetic ground state is reported. Local spin freezing associated with conventional spin-glass behavior is observed upon Fe substitution, marking an impurity-induced freezing of the primarily dynamic magnetic ground state in ${\mathrm{NaRuO}}_2$. Furthermore, local Fe moments induce a Curie-Weiss magnetic behavior in the uniform magnetic susceptibility, and the local moment magnitude is best described by dynamic Ru moments polarized about impurity sites. Our results establish an impurity-doping phenomenology consistent with inherently dynamic moments in ${\mathrm{NaRuO}}_2$ that are pinned by local magnetic impurities, similar to “swiss cheese” models of impurity-substituted copper oxides.

We report on ferroelectric behavior in wurtzite $\mathrm{Z}{\mathrm{n}}_{1-x}\mathrm{M}{\mathrm{g}}_x\mathrm{O}$ thin films across the accessible Mg concentration range. We outline a sputter deposition process for $\mathrm{Z}{\mathrm{n}}_{1-x}\mathrm{M}{\mathrm{g}}_x\mathrm{O}$ thin films using an oxygen/ozone environment to reduce electronic defects that limit insulation resistance. This procedure yields films that support ferroelectric hysteresis in Mg-substitution concentrations between $\sim 8\mathrm{mol}\%$ and 55 mol%. Generally, the remnant polarization has a modest composition dependence and all films show complete ferroelectric wakeup. Coercive fields initially fall with increasing Mg fraction and then increase above $\sim 13\mathrm{mol}\%$. The initial reduction is likely associated with structural softening via Mg substitution while the increase is likely associated with increased crystallographic disorder. The most resistive films reside in the 25–38 mol% Mg window. Electron microscopy reveals large stacking fault concentrations in as-deposited film microstructures consistent with sputtered ZnO. Chemical analysis suggests uniform Mg distribution in all films. For the test case in the Mg-rich regime, films become less resistive with decreasing thickness, but hysteresis is observable in a 66 nm layer.

Atomic vibrational dynamics in cuprite ${\mathrm{Cu}}_2\mathrm{O}$ was studied by inelastic neutron scattering and molecular-dynamics (MD) simulations from 10 K to 900 K. At 300 K, a diffuse inelastic intensity (DII) appeared in the phonon dispersions, and dominated the spectral intensity at higher temperatures. Classical MD simulations with a machine-learning interatomic potential reproduced general features of the DII. Better agreement with experiment was obtained with the addition of a stiffer potential at close approaches of the Cu and O-atoms. The DII originates from random phase shifts of vibrating O atoms that have brief ($\sim 10\mathrm{fs}$) anharmonic interactions with neighboring Cu atoms. The spectrum of DII gives information about the interaction time of anharmonic interactions between atoms, and its intensity gives a strength of coupling between vibrating atoms and a thermal bath.

Alloying metals improves their mechanical properties. In the case of Mg, alloying atoms, such as Cu and Al, act as microcathodes and accelerate corrosion. We establish the relationship between the corrosion mechanisms and avalanche dynamics as observed by acoustic emission (AE) spectroscopy. The micro-galvanic corrosion of Mg-Cu-Al alloys is simultaneously investigated under in situ conditions by AE and free-corrosion potential measurements, and optical observations. Three corrosion mechanisms are found, namely Mg matrix dissolution, crack propagation, and bubble burst. Mg matrix dissolution events show predominantly correlated avalanches with power law distributed AE signals. Their energy exponents decrease when initial sparse, localized corrosion events develop into large-scale corrosion. The crack propagation involves avalanches which accelerate micro-galvanic corrosion. To better understand the role of alloying of Mg we compare our results of a Mg-Cu-Al alloy with those of pure Mg. The incubation time in Mg alloys is much shorter (41 s versus 1236 s) than in pure Mg, and the initial attack regime is shortened (1236 s versus 1903 s). The power law exponents are generally reduced, and the power law regimes are wider in the Mg alloys than in pure Mg. The bubble bursts in the two materials are virtually identical. The statistical analysis demonstrates in situ monitoring of corrosion based on these techniques is possible.

Lamellar crystalline materials, whose layers are bound by van der Waals forces, can be stacked to form ultrathin artificial heterostructures and, in particular, vertical magnetic junctions when some of the stacked materials are (ferro)magnetic. Here, using the room temperature van der Waals ferromagnet $1T\text{−}{\mathrm{CrTe}}_2$, we report a method for patterning lateral magnetic junctions. Exploiting the heat-induced phase transformation of the material into ${\mathrm{Cr}}_x{\mathrm{Te}}_y$ compounds ($x/y>1/2$), we use local laser heating to imprint patterns at the micron-scale. Optimizing laser heat dissipation, we further demonstrate the crucial role of the substrate to control the phase transformation. If plain, unstructured poorly heat-conducting substrates allow for direct writing of magnetic patterns, structured $h$-BN layers can serve as heat stencils to draw potentially thinner patterns. Besides, $h$-BN encapsulation turns out to be heat-protective (in addition to protecting against oxidation, for which it is generally used), allowing the demonstration of room temperature ferromagnetism in $<7$ nm-thick $1T\text{−}{\mathrm{CrTe}}_2$.

We use molecular dynamics to calculate rate coefficients for recombination of vacancies with self-interstitial atoms (SIAs) in Cu at temperatures from 300 to 700 K. From these results, we calculate vacancy/SIA recombination volumes and find that they decrease from around 290Ω (where Ω is one atomic volume) at 300 K to 160Ω at 500 K and above. By counting the number of distinct pathways by which a stable SIA may migrate to a site of spontaneous recombination with a nearby vacancy, we find a lower bound estimate of 168Ω for the recombination volume. We furthermore rationalize its temperature dependence based on differences between the activation energies for recombination and SIA migration. Our work sheds light on the fundamental nature of the recombination volume and provides information that may be incorporated into multiscale models of radiation response in solids.

Altermagnets represent a new class of magnetic phases without net magnetization, invariant under a combination of rotation and time reversal. Unlike conventional collinear antiferromagnets (AFM), altermagnets could lead to new correlated states and important material properties deriving from their nonrelativistic spin-split band structure. Indeed, they serve as the magnetic analogue of unconventional superconductors and can yield spin-polarized electrical currents in the absence of external magnetic fields, making them promising candidates for next-generation spintronics. Here, we report altermagnetism in the correlated insulator, magnetically ordered tetragonal oxychalcogenide, $\mathrm{L}{\mathrm{a}}_2{\mathrm{O}}_3\mathrm{M}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_2$. Symmetry analysis reveals a $d_{x^2-y^2}$-wave-like spin-momentum locking arising from the $\mathrm{M}{\mathrm{n}}_2\mathrm{O}$ Lieb lattice, supported by density functional theory (DFT) calculations. Magnetic measurements confirm the AFM transition below $\sim 166\mathrm{K}$ while neutron pair distribution function analysis reveals a 2D short-range magnetic order that persists above the Néel temperature. Single crystals are grown and characterized using x-ray diffraction, optical and electron microscopy, and micro-Raman spectroscopy to confirm the crystal structure, stoichiometry, and uniformity. Our findings establish $\mathrm{L}{\mathrm{a}}_2{\mathrm{O}}_3\mathrm{M}{\mathrm{n}}_2\mathrm{S}{\mathrm{e}}_2$ as a model altermagnetic system realized on a Lieb lattice.

We report a substrate-limited, high-quality thin film growth of ${\mathrm{Co}}_2\mathrm{TiSn}$, requiring the use of a substrate-limited TiN buffer layer as well as a Nb capping layer to achieve an x-ray diffraction rocking curve full width at half-maximum of 12 arcseconds. This value represents more than an order of magnitude improvement over previous results for TiN, and more than two orders of magnitude better than any previous ${\mathrm{Co}}_2\mathrm{TiSn}$ thin film reported. Our surface analysis of the TiN film grown on a-plane sapphire reveals a distinctive step-edge-guided nucleation and epitaxial layer growth. Additionally, our first-principles calculations on ${\mathrm{Co}}_2\mathrm{TiSn}$ in its ${\mathrm{L}2}_1$ and XA phases examine the limitations of various exchange correlation functionals and the impact of Hubbard U correction on accurately representing the magnetic properties and density of states of ${\mathrm{Co}}_2\mathrm{TiSn}$. The observed lower-than-ideal magnetic moment in the disordered (XA) phase corresponds well with the experimentally observed reduced magnetization of the ${\mathrm{Co}}_2\mathrm{TiSn}$ film, as no evidence of phase segregation or secondary phase is detected. This work serves as both a roadmap for making high-quality Heusler alloy thin films and a stepping stone for the evaluation of the intrinsic atomic ordering in this and other Heusler systems by providing a high-quality crystal with energetics during formation as close to the thermodynamic limit as possible.

Understanding the atomistic mechanism in graphene growth is crucial for controlling the number of layers or domain sizes to meet practical needs. In this work, focusing on the growth of graphene by chemical vapor deposition on copper substrates, the surface kinetics in the growth are systematically investigated by first-principles calculations. The phase diagram, predicting whether the growth mode is monolayer graphene or bilayer graphene under various experimental conditions, is constructed based on classical nucleation theory. Our phase diagram well illustrates the effect of high hydrogen pressure on bilayer graphene growth kinetics and clarifies the mechanism of the most widely used experimental growth approaches. The phase diagram can provide guidance and predictions for experiments and inspire the study of other two-dimensional materials with graphenelike growth mechanisms.

We demonstrated x-ray structural analysis of the pressure-induced superconductor ${\beta }^{\prime }\text{−}{\mathrm{ET}}_2{\mathrm{ICl}}_2$ under extremely high pressure conditions, where ET denotes bis(ethylenedithio)tetrathiafulvalene. This material has been known as the highest transition temperature ($T_c$) superconductor among organic superconductors ($T_c=14.2\mathrm{K}$ at 8.2 GPa). On the basis of the experimental results, ab initio models were derived using the constrained random phase approximation. We revealed that the Lifshitz transition exists behind the Mott insulator–imetal transition and found that the value of the on-site Coulomb interaction was halved to around $10\mathrm{GPa}$ compared to that at ambient pressure. This Letter clarifies the enigmatic origins of high $T_{\mathrm{c}}$ and, concurrently, provides an understanding of the impacts of structural alterations in organic materials under high pressure on their electronic properties and the superconductivity process.