The antiferromagnetic transition metal oxyhydride ${\mathrm{SrVO}}_2\mathrm{H}$ is distinguished by its stoichiometric composition and an ordered arrangement of H atoms. The tetragonal structure is related to the cubic perovskite and consists of alternating layers of ${\mathrm{VO}}_2$ and SrH. $d^2$ V(III) attains a sixfold coordination by four O and two H atoms. The latter are arranged in a trans fashion, which produces H–V–H chains along the tetragonal axis. Here, we investigate the vibrational properties of ${\mathrm{SrVO}}_2\mathrm{H}$ by inelastic neutron scattering and infrared spectroscopy combined with phonon calculations based on density functional theory. The H-based vibrational modes divide into a degenerate bending motion perpendicular to the H–V–H chain direction and a highly dispersed stretching motion along the H–V–H chain direction. The bending motion, with a vibrational frequency of approximately 800 ${\mathrm{cm}}^{-1}$, is split into two components separated by about 50 ${\mathrm{cm}}^{-1}$, owing to the doubled unit cell from the antiferromagnetic structure. Interestingly, spin-phonon coupling stiffens the H-based modes by $50-100{\mathrm{cm}}^{-1}$ although super-exchange coupling via H is very small. Frequency shifts of the same order of magnitude also occur for V–O modes. It is inferred that ${\mathrm{SrVO}}_2\mathrm{H}$ displays the hitherto largest recognized coupling between magnetism and phonons in a material.

Using first-principles calculations in combination with the Eliashberg formalism, we systematically investigated phonon-mediated superconductivity in two-dimensional (2D) metal-boride crystals, consisting of a boron honeycomb network doped by diverse metal elements. Such 2D metal-boride compounds, named MBenes, are chemically exfoliable from single-crystalline layered ternary borides. First we identified the MBene layers with potential for superconductivity via isotropic Eliashberg calculations, considering a wide range of metal elements, with a focus on alkaline earth and transition metals. Subsequently, we performed a detailed analysis of the prominent superconducting MBenes by solving the anisotropic Eliashberg equations. The obtained high critical temperatures (up to 72 K), as well as the rich multigap superconducting behavior, recommend these crystals for further use in multifunctional 2D heterostructures and superconducting device applications.

We investigated the electronic and hydration structures of montmorillonite (MMT) and beidellite (BEI) using a first-principles method combined with classical solution theory. Both MMT and BEI belong to a family of clay minerals with a layered structure containing water molecules and cations in the interlayer. First, we optimized the number of accumulated water molecules in the interlayer space and found the present results to be in reasonable agreement with previous experiments. Next, we refined the positions of the cations to determine the most stable structure based on the adsorption energy of the clay layers. We found that the cations in the interlayer stably adsorb to the clay layers and the most stable adsorption site is the center of the six-membered ring. The hydration structure strongly depends on the cation adsorption structure based on the charge density distribution of the water. In contrast, the electronic state is weakly dependent on the adsorption structure because of its insulating electronic structure. Therefore, our results strongly suggest that the physical properties of MMT and BEI arise from changes in the hydration structure induced by cation adsorption/desorption.

Thermodynamics controls structure, function, stability, and morphology of polymer blends. However, obtaining the precise information about their mixing thermodynamics is a challenging task, especially when dealing with complex macromolecules. This is partially because of a delicate balance between the local concentration/composition fluctuations and the monomer level (multibody) interactions. In this context, the Kirkwood-Buff (KB) theory serves as a useful tool that connects the local pairwise fluid structure to the mixing thermodynamics. Using larger scale molecular dynamics simulations, within the framework of KB theory, we investigate a set of technologically relevant poly(methyl methacrylate)-poly(lactic acid) blends with the aim to elucidate the underlying microscopic picture of their phase behavior. Consistent with the existing experiments, we emphasize the importance of properly accounting for the entropic contribution to the mixing Gibbs free-energy change $\mathrm{\Delta }{\mathcal{G}}_{\mathrm{mix}}$ that controls the phase morphology. We further show how the relative microscopic interaction details and the molecular level structures between different mixing species can control the nonlinear mechanics, ductility, and heat flow. Therefore, this study provides a guiding principle for the design of light weight functional materials with extraordinary physical properties.

The electronic rendition of the Hanle effect, which is interpreted as the ensemble dephasing of a spin accumulation in the semiconductor under a perpendicular magnetic field, has been one of the most widely utilized and effective methods of measuring spin lifetime, spin accumulation, and spin transport in semiconductors. However, the origin of the Hanle magnetoresistance in the three-terminal (3T) setup has been intensively questioned both theoretically and experimentally; this is in contrast to the nonlocal four-terminal (NL-4T) measurement, which is accepted as reflecting spin accumulation and its spatial decay in metals and semiconductors alike. Here, we present results from 3T and NL-4T Hanle measurements on the same spin injection and detection devices with an ${\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}:\mathrm{Si}$ semiconducting channel. The use of ${\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}:\mathrm{Si}$, a persistent photoconductor, enables examination of the evolution of both types of Hanle signals with varying carrier density in the channel on one and the same device via in situ photodoping. We observe that the 3T and NL-4T Hanle signals exhibit similar Lorentzian line shapes, and thus yield similar spin lifetimes at all carrier densities. Moreover, the amplitudes of both types of Hanle signals are found to be consistent with each other, showing a similar exponential decrease with carrier density and in agreement with the Valet-Fert theory, in contrast to devices with artificial oxide barriers. These observations provide compelling evidence that in devices in which the spin injectors and detectors are engineered to minimize the presence of localized states, the 3T Hanle measurements provide a reliable probe of the spin accumulation and its dynamics in the semiconductor channel.

Understanding the resistance of soft materials to puncture bears relevance to many fields. However, the complex mechanics during deep indentation make it difficult to disentangle how the different dissipation processes contribute to the fracture energy and how this depends on the molecular structure of the material. To investigate this, we perform deep indentation experiments with a flat-ended cylindrical probe on polymer networks containing the covalently incorporated mechanoluminescent bond rupture sensor 1,2-dioxetane. By carrying out the experiments inside an integrating sphere, we are able to quantify the number of ruptured bonds during puncture nucleation and propagation. We find that puncture is associated with significant diffuse damage, both prior to nucleation of the main crack and during crack propagation. Moreover, in agreement with earlier results for uniaxial extension, we show that puncture of double networks leads to strongly enhanced rupture in the prestretched sacrificial network, while fracture of the matrix network is much more localized. Finally, we complement the experiments with MD simulations that allow us to link the rupture processes to the distribution of tension in the networks.

Over the last two decades organic spintronics has developed into a striving field with exciting reports of long spin diffusion lengths and spin relaxation times in organic semiconductors (OSCs). Easily processed and inexpensive, OSCs are considered a potential alternative to inorganic materials for use in spintronic applications. Spin currents have been detected in a wide range of materials; however, there is still uncertainty over the origin of the signals. Recently, we explored spin transport through an organic semiconductor with lateral spin injection and detection architectures, where the injected spin current is detected nonlocally via spin-to-charge conversion in an inorganic detector. In this work we show that the widely used control experiments like linear power dependence and inversion of the signal with the magnetic field are not sufficient evidence of spin transport and can lead to an incorrect interpretation of the signal. Here, we use in-plane angular dependent measurements to separate pure spin signal from parasitic effects arising from spin rectification. Apart from well established anisotropic magnetoresistance and the anomalous Hall effect, we observe another spurious effect originating in Py and having the same angular symmetry as the inverse spin Hall effect (ISHE), which suggests it might be a self-induced ISHE.

Semiconductor nanowires have emerged as versatile components in superconducting hybrid devices for Majorana physics and quantum computing. The transport properties of nanowires can be tuned either by field effect or doping. We investigated a series of InAs nanowires the conductivity of which has been modified by $n$-type doping using tellurium. In addition to electron microscopy studies, the wires were also examined with atomic probe tomography to obtain information about the local incorporation of Te atoms. It was found that the Te atoms mainly accumulate in the core of the nanowire and at the corners of the {110} side facets. The efficiency of $n$-type doping was also confirmed by transport measurements. As a demonstrator hybrid device, a Josephson junction was fabricated using a nanowire as a weak link. The corresponding measurements showed a clear increase of the critical current with increase of the dopant concentration.

We propose a minimalist coarse-grained microscopic model to investigate the mechanical response of ice-templated polymer nanocomposite sponges with large open voids. Earlier experimental work [Rajamanickam et al., Chem. Mater. 26, 5161 (2014)] has demonstrated that such systems show elastic recovery after being subjected to large compressive strains exceeding $80\%$, despite being comprised primarily of inorganic nanoparticles. Our model captures the essential features of the nonlinear mechanical response to uniaxial compression up to strain $\gamma =0.8$. From our simulation we identify three different regimes for the stress response: (i) the stress increases linearly with strain at low strains up to $\approx 0.2$; (ii) at intermediate strains, such that $\gamma$ is approximately in the range $0.2-0.5$, we observe a plateau regime in the stress-strain data; and (iii) finally we see a sharp increase in stress at strains $>0.5$. This agrees with experimental observations. The model helps us establish a correlation between the stress-strain response and the underlying microscopic reorganization of microstructure spanning multiple length scales, which leads to the emergence of the three regimes. The nature of individual void deformations was statistically analysed to demonstrate the progression of void shapes as the sponge is compressed. We also establish that nanoparticles at the interface of voids respond differently to stress as compared to those away from the interface. Our simulation model is versatile and allows us to vary parameters, which correspond to variations in the cross-link density and architecture of nanoparticle connectivity in experiments.

We compare the magnetism of single crystals of the intercalated transition metal dichalcogenides ${\mathrm{Cr}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ and ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ using techniques such as dc and ac susceptibility and Lorentz transmission electron microscopy (LTEM). We present a detailed structural investigation of these materials using electron and single-crystal x-ray diffraction measurements to show how substitutional disorder and stacking faults can manifest in ${\mathrm{Cr}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ and ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$, and give rise to additional superlattice reflections in diffraction patterns acquired from ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$. Magnetic susceptibility and LTEM measurements show ${\mathrm{Cr}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ displays chiral helimagnetism below its magnetic ordering temperature ($T_{\mathrm{C}}$) of 111 K, while there is no evidence that ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ exhibits helimagnetic ordering below its transition temperature $T_{\mathrm{C}}=45$ K.

We theoretically study the carrier doping effect for magnetism in the stacked-kagome system ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ based on an effective model and the Hartree-Fock method. We show the electron filling and temperature dependencies of the magnetic order parameter. The perpendicular ferromagnetic ordering is suppressed by hole doping, whereas undoped ${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ shows a magnetic Weyl semimetal state. Additionally, in the electron-doped regime, we find a noncollinear antiferromagnetic ordering. Especially, in the noncollinear antiferromagnetic state, by considering a certain spin-orbit coupling, the finite orbital magnetization and the anomalous Hall conductivity are obtained.

Magnetic doping of topological quantum materials provides an attractive route for studying the effects of time-reversal symmetry breaking. Thus motivated, we explore the introduction of the transition metal Mn into thin films of the Dirac semimetal ${\mathrm{Cd}}_3{\mathrm{As}}_2$ during growth by molecular beam epitaxy. Scanning transmission electron microscopy measurements show the formation of a Mn-rich phase at the top surface of Mn-doped ${\mathrm{Cd}}_3{\mathrm{As}}_2$ thin films grown using both uniform doping and delta doping. This suggests that Mn acts as a surfactant during epitaxial growth of ${\mathrm{Cd}}_3{\mathrm{As}}_2$, resulting in phase separation. Magnetometry measurements of such samples indicate a ferromagnetic phase with out-of-plane magnetic anisotropy. Electrical magneto-transport measurements of these films as a function of temperature, magnetic field, and chemical potential reveal a lower carrier density and higher electron mobility compared with pristine ${\mathrm{Cd}}_3{\mathrm{As}}_2$ films grown under similar conditions. This suggests that the surfactant effect might also serve to remove impurities from the bulk of the film. We observe robust quantum transport (Shubnikov-de Haas oscillations and an incipient integer quantum Hall effect) in very thin (7 nm) ${\mathrm{Cd}}_3{\mathrm{As}}_2$ films despite being in direct contact with a structurally disordered surface ferromagnetic overlayer.

Due to its half metallic nature, ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ is an attractive highly correlated electronic system to obtain ultralow magnetic damping. In this paper we analyze the temperature and thickness dependence of the damping of the magnetization dynamic of epitaxial thin ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ films. Our analysis reveals that the damping encompasses resistivelike and conductivelike contributions, as in transition metal ferromagnets. The data also show a large increase of the ferromagnetic resonance linewidth at low temperature, a feature that we ascribe to the presence of a dead layer, insulating and magnetically active, that behaves like a spin sink. The associated spin-pumping term shows a strong temperature dependence, linked to that of the spin mixing conductance. By clarifying some unexplored aspects of spin dynamics in half-metallic manganites, our results contribute to the progress in the burgeoning field of oxide spin orbitronics.

We used 4D ultrafast electron microscopy (UEM) to directly image femtosecond photoinduced structural dynamics in single-crystal LaFeAsO at initial temperatures of 300 and 100 K, above and below the known structural and magnetic phase-transition temperatures, respectively. With nanometer-picosecond resolution, we resolved an initial (precursor) sigmoidlike response arising from photothermal expansion and lattice reorientation that precedes the onset of propagating coherent acoustic phonons (CAPs). In the specific regions probed, the precursor response at 100 K is shorter than at 300 K ($t_{0.5;100\mathrm{K}}=11.3\mathrm{ps}$ vs $t_{0.5;300\mathrm{K}}=17.8\mathrm{ps}$), and the CAP oscillation frequency is lowered with cooling ($f_{\mathrm{CAP};100\mathrm{K}}=12\mathrm{GHz}$ vs $f_{\mathrm{CAP};300\mathrm{K}}=21\mathrm{GHz}$), correlated to known lattice softening due to the structural phase change. The transient CAP behaviors at 300 K are dispersive, displaying an exponentially decaying phase velocity over the first nanosecond. Further, the CAP symmetry at 300 K matches a first-order antisymmetric shear mode ($A_1$), while at 100 K it is best matched by a mostly nondispersive zero-order symmetric mode ($S_0$). These findings illustrate the sensitivity of UEM imaging to spatially heterogeneous dynamics in the Fe-pnictide materials and more broadly in other quantum materials.

Exceptionally high experimental photoluminescence quantum yields attributed to highly efficient quantum cutting have recently been observed in ytterbium-doped inorganic metal-halide perovskites such as Yb:CsPb($X=$ Cl, ${\mathrm{Br})}_3$. Combined with strong, tunable, broadband absorption in the visible spectrum, these materials show great promise for applications in solar down-converter technologies. Much subsequent work has been dedicated to uncovering the fundamental mechanisms behind Yb-mediated quantum cutting, and an accumulation of experimental evidence has shown that a particular speciation of Yb, believed to be a fully compensated ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^0$ defect complex, dominates this process. In this work, we investigate Yb defect formation in single-crystal ${\mathrm{CsPbCl}}_3$, and in particular the feasibility of forming ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^0$ defect complexes, using first-principles electronic structure calculations. A simple thermodynamic model based on defect formation energies, binding energies, and charge transition levels provides some insight into the distribution of ${\mathrm{Yb}}_{\mathrm{Pb}}$ substitutionals and Pb vacancies, underscoring the range of material compositions and synthesis conditions over which locally bound configurations of ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^0$ defect complexes become significant. We complement this analysis with additional calculations of structural and electronic properties and discuss the consistency of these results with the observed onset of quantum cutting.

Two-dimensional (2D) MXenes are a rapid growing family of 2D materials with rich physical and chemical properties where their surface termination plays an essential role. Among the various 2D MXenes, functionalization of the ${\mathrm{Ti}}_n{\mathrm{C}}_{n-1}$ phase with oxygen (O) atoms makes them attractive for optoelectronic applications due to their optical gap residing in the infrared or visible region. In this paper, we theoretically investigate the electronic and optical properties of four different O-atom-functionalized ${\mathrm{Ti}}_n{\mathrm{C}}_{n-1}$ MXene monolayers using state-of-the-art, first-principles techniques. In particular, we calculate the quasiparticle corrections on top of density functional theory (DFT) with the GW approximation and the exciton-dominated optical spectra by solving the Bethe-Salpeter equation also at finite momentum. We find that all but one of the monolayer models are indirect band-gap semiconductors where quasiparticle corrections are very important ($\sim 1$ eV). The optical spectra are instead dominated by direct and indirect excitons with large binding energies (between 0.5 and 1 eV). Most direct excitons lie above 1.5 eV, while the indirect ones are below; therefore, we conclude that ${\mathrm{Ti}}_n{\mathrm{C}}_{n-1}$ should display strong absorption in the visible region, but phonon-assisted emission in the infrared. Our work thus reveals the potential usage of surface terminations to tune the optical and electronic properties of ${\mathrm{Ti}}_n{\mathrm{C}}_{n-1}$ MXene monolayers, while emphasizing the pivotal role of many-body effects beyond DFT to obtain accurate prediction for these systems.

Automatic exhaustive exploration of a large material space by high-performance supercomputers is crucial for developing new functional materials. We demonstrated the efficiency of high-throughput calculations using the all-electron Korringa-Kohn-Rostoker coherent potential approximation method with the density functional theory for the large material space consisting of quaternary high entropy alloys, which are nonstoichiometric and substitutionally disordered materials. The exhaustive calculations were performed for 147 630 systems based on the AkaiKKR program package and supercomputer Fugaku, where the numerical parameters and self-consistent convergence are automatically controlled. The large material database including the total energies, magnetization, Curie temperature, and residual resistivity was constructed by our calculations. We used frequent itemset mining to identify the characteristics of parcels in magnetization and Curie temperature space. We also identified the elements that enhance the magnetization and Curie temperature and clarified the rough dependence of the elements through regression modeling of the residual resistivity.

Predicting the behavior of complex systems is one of the main goals of science. An important example is plastic deformation of micron-scale crystals, a process mediated by collective dynamics of dislocations, manifested as broadly distributed strain bursts and significant sample-to-sample variations in the response to applied loading. Here, by combining large-scale discrete dislocation dynamics simulations and machine learning, we study the problem of predicting the fluctuating stress-strain curves of individual small single crystals subject to strain-controlled loading using features of the initial dislocation configurations as input. Our results reveal an intriguing rate dependence of deformation predictability: For small strains predictability improves with increasing strain rate, while for larger strains the predictability vs strain rate relation becomes nonmonotonic. We show that for small strains the rate dependence of deformation predictability can be captured by considering the fraction of dislocations moving against the direction imposed by the external stress, serving as a measure of strain-rate-dependent complexity of the dislocation dynamics. The nonmonotonic predictability vs strain rate relation for large strains is argued to be related to a transition from fluctuating to smooth plastic flow when strain rate is increased.

Dense, disordered packings of particles are useful models of low-temperature amorphous phases of matter, biological systems, granular media, and colloidal systems. The study of dense packings of nonspherical particles enables one to ascertain how rotational degrees of freedom affect packing behavior. Here, we study superballs, a large family of deformations of the sphere, defined in three dimensions by $|x_1{|}^{2p}+|x_2{|}^{2p}+{\left|x_3\right|}^{2p}\le 1$, where $p\in (0,\infty )$ is a deformation parameter indicating to what extent the shape deviates from a sphere. As $p$ increases from the sphere point ($p=1$), the superball tends to a cuboidal shape and approaches a cube in the $p\to \infty$ limit. As $p\to 0.5$, it approaches an octahedron, becomes a concave body with octahedral symmetry for $p<0.5$, and approaches a three-dimensional cross in the limit $p\to 0$. Previous characterization of superball packings has shown that they have a maximally random jammed (MRJ) state, whose properties (e.g., packing fraction $\varphi$, average contact number $\overline{Z}$) vary nonanalytically as $p$ diverges from unity. Here, we use an event-driven molecular dynamics algorithm to produce MRJ superball packings with $0.85\le p\le 1.50$. To supplement the previous work on such packings, we characterize their large-scale structure by examining the behaviors of their structure factors $S\left(Q\right)$ and spectral densities ${\tilde{\chi }}_{{}_V}\left(Q\right)$, as the wave number $Q$ tends to zero, and find that these packings are effectively hyperuniform for all values of $p$ examined. We show that the mean width $\overline{w}$ is a useful length scale to make distances dimensionless in order to compare systematically superballs of different shape. Moreover, we compute the complementary cumulative pore-size distribution $F\left(\delta \right)$ and find that the pore sizes tend to decrease as $|1-p|$ increases. From $F\left(\delta \right)$, we estimate how the fluid permeability, mean survival time, and principal diffusion relaxation time vary as a function of $p$. Additionally, we compute the diffusion “spreadability” $\mathcal{S}\left(t\right)$ [Torquato, Phys. Rev. E 104, 054102 (2021)] of these packings and find that the long-time power-law scaling indicates these packings are hyperuniform with a small-$Q$ power law scaling of the spectral density ${\tilde{\chi }}_{{}_V}\left(Q\right)\sim Q^{\alpha }$ with an exponent $\alpha$ that ranges from 0.64 at the sphere point to 0.32 at $p=1.50$, and decreases as $|1-p|$ increases. Each of the structural characteristics computed here exhibits an extremum at the sphere point and varies nonanalytically as $p$ departs the sphere point. We find the nonanalytic behavior in $\varphi$ on either side of the sphere point is nearly linear, and determine that the rattler fraction ${\varphi }_R$ decreases rapidly as $|1-p|$ increases. Our results can be used to help inform the design of colloidal or granular materials with targeted densities and transport properties.