The emergence of shear bands is the universal cause of material failure in metallic glasses. In spite of relentless spirit, the structural origin, especially down to atomic level, of shear banding emergence is still an open question in disordered solids. Here, careful atomic simulations are carried out in $\mathrm{C}{\mathrm{u}}_{50}\mathrm{Z}{\mathrm{r}}_{50}$ metallic glasses with various cooling histories. The icosahedral network formed by connected icosahedral clusters is recognized as the structural link between the glass formation process and shear banding emergence. First of all, it is found that the dominant structural evolution of glass transition is the competition between newly activated icosahedral clusters and the connection of existing ones. The glassy state as well as dynamics is then characterized by the level of connectivity of icosahedral clusters. This is evidenced by the power-law relation between the connectivity level and the relaxation time. Such connected icosahedral network is further found as the structural origin of the emergent inhomogeneous deformation field as well as the ultimate shear banding emergence upon loading. The emergence of shear bands is thus demonstrated as the collapse of the icosahedral network, which can be characterized as a “core-shell” structure in terms of our previously developed two-term gradient model. It is carefully demonstrated that atoms in the shell participate in dilatation and shear events while atoms in the inner core mainly undertake rotation motion. Our findings elaborate detailed physical images by tracing back to the critical glass transition process which provides a perspective in understanding the shear banding emergence.

III-V nanowire (NW) heterostructures are promising candidates for advanced silicon-integrated optoelectronics and quantum light sources. The interfacial abruptness in axial NW heterostructures grown by the vapor-liquid-solid (VLS) method suffers from the reservoir effect in a catalyst droplet. The interfaces of NW heterostructures based on group V interchange are commonly expected to be sharper due to low concentrations of highly volatile group V atoms in a droplet. Here, we present a self-consistent growth model of VLS III-V NW heterostructures based on group V interchange, influenced by desorption of group V atoms, and show that sharp interfaces are not guaranteed in the general case. The model provides explicitly the interfacial profiles across double NW heterostructure of any composition. The obtained solution contains only one parameter describing different transport of $A$ and $B$ atoms through liquid. The interfacial abruptness depends critically on a binary or ternary NW from which it starts, as well as on the stationary composition of the second segment. We analyze the available experimental data and explain why the interfacial profiles in $\mathrm{Ga}{\mathrm{As}}_x{\mathrm{P}}_{1-x}/\mathrm{Ga}\mathrm{As}/\mathrm{Ga}{\mathrm{As}}_x{\mathrm{P}}_{1-x}$ NWs are much sharper than in $\mathrm{GaP}/\mathrm{Ga}{\mathrm{As}}_x{\mathrm{P}}_{1-x}/\mathrm{GaP}$ NWs. The effect originates from a slower transport of As atoms in any catalyst as compared to P atoms. As a result, feeding and removing As atoms in the GaP-to-$\mathrm{Ga}{\mathrm{As}}_x{\mathrm{P}}_{1-x}$ transitions is much slower than for P atoms in the GaAs-to-$\mathrm{Ga}{\mathrm{As}}_x{\mathrm{P}}_{1-x}$ transitions with similar $x$. Our approach should be useful for tuning the composition and sharpening the interfaces of any III-V NW heterostrutures based on group V interchange, and provides a basis for further advancements in this field.

The diffusive phase transformations occurring in feldspar, a common mineral in the crust of the Earth, are essential for reconstructing the thermal histories of magmatic and metamorphic rocks. Due to the long timescales over which these transformations proceed, the mechanism responsible for sodium diffusion and its possible anisotropy has remained a topic of debate. To elucidate this defect-controlled process, we have developed a neural network potential (NNP) trained on first-principle calculations of Na-feldspar (albite) and its charged defects. This force field reproduces various experimentally known properties of feldspar, including its lattice parameters and elastic constants as well as heat capacity and DFT-calculated defect formation energies. A new type of dumbbell interstitial defect is found to be most favorable, and its free energy of formation at finite temperature is calculated using thermodynamic integration. The necessity of including electrostatic corrections before training an NNP is demonstrated by predicting more consistent defect formation energies.

Two-dimensional van der Waals single crystals DyOBr and SmOCl have been grown by a flux method, and their anisotropic magnetic properties are reported. DyOBr orders antiferromagnetically at $T_{\mathrm{N}}=9.5\mathrm{K}$ with magnetic moments lying along $a$ axis, similar as DyOCl. Its magnetic susceptibility shows an anomaly at $T^{*}=30\mathrm{K}$, possibly due to the crystal field effect. Furthermore, a 1/3 magnetization plateau is clearly observed under $H\parallel a$ and $H\parallel \left[110\right]$, which might be a field-induced spin-flop phase or some exotic quantum magnetic state. On the other hand, isostructural SmOCl undergoes an antiferromagnetic transition at $T_{\mathrm{N}}=7.1\mathrm{K}$ and exhibits a contrasting Ising-like perpendicular $c$-axis magnetic anisotropy, which could be well explained by our crystal field calculations. Both DyOBr and SmOCl are insulators with a band gap of $\sim 5\mathrm{eV}$, and our results suggest they are promising in building van der Waals heterostructures and applications in multifunctional devices.

The Photonic Atom Probe is applied to the study of nanoscale field-emission tip specimens containing a section of III-N device constituted by a sequence of alloyed and doped sections. Different sections produce specific but spectrally overlapping luminescence signals. The possibility of collecting photoluminescence spectra during the field evaporation of the specimen allows for disentangling different doping-related luminescence lines and to correlate the different spectral contributions to the specific properties of the doping distributions. In particular, the spectral components of the luminescence related to Mg impurities at energies between 3.0 eV and 3.3 eV have been investigated, and correlated with the Mg concentration and 3D distribution in different sections of the device.

Epitaxially grown ${\mathrm{RuO}}_2$ films on ${\mathrm{TiO}}_2$ (110) exhibit significant in-plane strain anisotropy, with a compressive strain of −4.7% along the [001] crystalline direction and a tensile strain of +2.3% along $\left[1\overline{1}0\right]$. As the film thickness increases, anisotropic strain relaxation is expected. By fabricating Hall bar devices with current channels along two in-plane directions, $\langle 001\rangle$ and $\langle 1\overline{1}0\rangle$, we reveal anisotropic in-plane transport in $\mathrm{Ru}{\mathrm{O}}_2/\mathrm{Ti}{\mathrm{O}}_2$ (110) films grown via the solid-source metal-organic molecular beam epitaxy approach. For film thicknesses $\left(t_{\mathrm{film}}\right)\le 3.6$ nm, the resistivity along $\langle 001\rangle$ exceeds that along the $\langle 1\overline{1}0\rangle$ direction at all temperatures. With further decrease in film thickness, we uncover a transition from metallic to insulating behavior at $t_{\mathrm{film}}\le 2.1$ nm. Our combined temperature- and magnetic field-dependent electrical transport measurements reveal that this transition from metallic to insulating behavior is driven by electron-electron interactions.

Although the use of two-dimensional materials for hydrogen storage has been intensively studied, finding reversible hydrogen storage material with high hydrogen gravimetric density under environmental conditions remains challenging. In this study, a new two-dimensional BN-biphenylene with Li decoration is systematically investigated through density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations. The DFT results reveal that the average binding energy between Li and BN-biphenylene monolayers can be significantly improved from −0.9 eV to −3.34 eV by doping two C atoms at N sites. In this sense, each Li atom can adsorb three ${\mathrm{H}}_2$ molecules, yielding a high ${\mathrm{H}}_2$ weight density of 12.54 wt%. Meanwhile, considering the corresponding ${\mathrm{H}}_2$ desorption temperature at the ideal environmental condition of 323.89 K, Li-modified C-doped BN-biphenylene monolayer can be treated as a promising reversible candidate for high-density hydrogen storage. In addition, GCMC simulation results also prove that the ${\mathrm{H}}_2$ storage capacity of Li-modified C-doped BN-biphenylene can reach an ultrahigh 13.28 wt% under 298 K and 1 bar. The present study provides a positive and valuable reference for exploring ultrahigh-capacity reversible hydrogen storage materials under environmental conditions.

ScN is an emerging transition metal nitride with unique physical properties arising from the $d$ electrons of Sc. In this letter, we present the results of optical characterization techniques: spectroscopic ellipsometry, Raman spectroscopy, and photoluminescence measurements of a $40\text{−}\mu \mathrm{m}$-thick fully relaxed, and only weakly $n$-type doped ($n=1.2\times {10}^{18}{\mathrm{cm}}^{-3}$) ScN film deposited by halide vapor phase epitaxy (HVPE) on r-sapphire substrate. Spectroscopic ellipsometry yields an indirect band gap of $1.1\mathrm{eV}$, while the lowest direct interband transition is observed at $E_{\mathrm{g},\mathrm{opt}}=2.16\mathrm{eV}$ in the dielectric function. A broad luminescence feature at $2.15\mathrm{eV}$ is observed, matching this transition. We derive an estimate for the exciton binding energy ($E_{\mathrm{bX}}\approx 14\mathrm{meV}$) as well as the Born effective charges $Z_{\mathrm{Sc}}^{*}=-Z_{\mathrm{N}}^{*}=3.81$. In the infrared spectral region, we observe a strong phonon and a weak plasmon absorption. We precisely determine the transverse optical (TO) phonon eigenfrequency (${\omega }_{\text{TO}}=340.7{\mathrm{cm}}^{-1}$), the high frequency dielectric constant (${\varepsilon }_{\infty }=8.3$), and the static dielectric constant (${\varepsilon }_{\text{stat}}=29.5$). Raman measurements using various excitation energies show resonant multiphonon scattering up to 6LO [sixth-order overtone for longitudinal optical (LO) phonons] for excitation above the optical band gap ($E_{\text{Laser}}>E_{\mathrm{g},\text{opt}}$), where the allowed $2\mathrm{LO}$ scattering is the dominant scattering mechanism for all excitation energies. Their characteristic parameters determined from Lorentzian line shape fitting yield ${\omega }_{\text{LO}}=684.5{\mathrm{cm}}^{-1}$ and an increased broadening for higher LO scattering order $n$.

We have investigated the magnetotransport properties for solid-solution thin films of ${\mathrm{Nd}}_{1-x}{\mathrm{Pr}}_x{\mathrm{RuO}}_3$ and ${\mathrm{Nd}}_{1-y}{\mathrm{Sm}}_y{\mathrm{RuO}}_3$ prepared through a solid phase epitaxy. It is found that the peculiar magnetotransport properties that emerge in ${\mathrm{NdRuO}}_3$ are modified by the systematic control of the electron correlation strength through the tuning of the bandwidth as well as in the total angular momentum $J$ of rare earth magnetic ions. The transition from metal to insulator is observed with increasing the concentration $y$ of smaller ${\mathrm{Sm}}^{3+}$ in ${\mathrm{Nd}}_{1-y}{\mathrm{Sm}}_y{\mathrm{RuO}}_3$, while ${\mathrm{Nd}}_{1-x}{\mathrm{Pr}}_x{\mathrm{RuO}}_3$ is kept metallic with increasing $x$ for larger ${\mathrm{Pr}}^{3+}$. An anomalous Hall effect is observed for all the conducting samples with the maximum Hall angle appearing for ${\mathrm{NdRuO}}_3$. The topological Hall effect observed for ${\mathrm{NdRuO}}_3$ gradually diminishes with increasing the doping concentrations $x$ and $y$.

Metal phosphorus trichalcogenides ($\mathrm{MP}{\mathrm{X}}_3$) constitute a vast family of van der Waals materials, comprising more than four dozen candidates with versatile properties spanning spin crossover, catalysis, and pressure-induced superconductivity. While exceptions exist, such as $\mathrm{SnPS}{\mathrm{e}}_3$, which adopts both 2D and 3D crystalline structures, with its 2D isomer recently exhibiting superconductivity under high pressure, the investigation of its 3D counterpart presents an intriguing opportunity to explore the dimensional influence on superconductivity. Here, we present detailed high-pressure measurements of bulk $\mathrm{SnPS}{\mathrm{e}}_3$, integrating electrical transport measurements, synchrotron diffraction, and theoretical structure predictions. Our findings reveal a monoclinic ($\mathrm{P}{2}_1/\mathrm{c}$, No. 14) to orthorhombic (Cmcm, No. 63) phase transition in $\mathrm{SnPS}{\mathrm{e}}_3$ at $P=22\mathrm{GPa}$, which remains crystalline to 50.5 GPa. Concurrent with this structural change, $\mathrm{SnPS}{\mathrm{e}}_3$ undergoes a semiconductor-superconductor transition at 18.9 GPa. Furthermore, as pressure increases, the transition temperature ($T_{\mathrm{c}}$) monotonically rises to 6.9 K at 85.6 GPa. This behavior sharply contrasts with that of reported 2D $\mathrm{SnPS}{\mathrm{e}}_3$, where a relatively higher $T_{\mathrm{c}}$ is achieved accompanied with amorphization at around 30 GPa. The notable difference in structural stability and superconductivity thus renders $\mathrm{SnPS}{\mathrm{e}}_3$ a clean and ideal platform for exploring additional unforeseen dimensional effects.

We study the dynamic deformation of columns containing a periodic array of holes subject to impact loading. When compressed slowly, holey columns buckle beyond a critical compressive strain, and global pattern switching (from circular holes to orthogonal ellipses) occurs instantaneously. In contrast, the dynamic deformation of holey columns is driven by wave propagation; impact induces a compressive wave that buckles the ligaments surrounding a hole, nucleating a sequential pattern switching process. Subsequent void collapse, which ultimately leads to self-contact and topological modification, is driven by the moving boundary. Here, we identify the critical impact velocity above which the compression can no longer be considered quasistatic, and we show that it depends on system size. For dynamic deformations, we show that internal displacements are independent of impact velocity and propagate at the material sound speed, whereas the topological transition wave propagates at a speed that depends on the impact velocity.

Polarized Raman spectroscopy offers the capability to study the interactions between electrons/excitons and phonons in the presence of intervalley scattering within two-dimensional materials. This study explores the relation between phonon symmetry and exciton-phonon interactions in monolayer and bilayer ${\mathrm{MoS}}_2$ using polarization-resolved photoluminescence and Raman spectroscopy. The resonant second-order Raman spectra in ${\mathrm{MoS}}_2$ are closely tied to material properties and laser excitation energy. Experimental and numerical analyses systematically examined phonon symmetry in Raman scattering, revealing a strong correlation between phonon symmetry and spin-valley polarization, especially under resonant excitation. Resonant excitation changed Raman scattering polarization because of the dominant Fröhlich interaction. The strong spin-orbit coupling in monolayer ${\mathrm{MoS}}_2$ unaffected by thermal vibrations at low temperatures leads to a notable increase in the valley polarization resulting from the restricted energy-level distribution of electron transitions. This phenomenon significantly influences the b mode in second-order resonant Raman scattering, consequently altering the chirality of phonon vibrations. We further propose a mechanism diagram elucidating the interaction between electrons and excitons of intervalley scattering. The study highlights the interplay between electron transitions and phonon-related behaviors in ${\mathrm{MoS}}_2$, emphasizing the significance of electron/exciton-phonon interactions under varying excitation energies and temperatures. These insights hold crucial implications for the optoelectronic applications of ${\mathrm{MoS}}_2$.

The recent synthesis of two-dimensional (2D) ${\mathrm{MoSi}}_2{\mathrm{N}}_4$ and ${\mathrm{WSi}}_2{\mathrm{N}}_4$ crystals has given rise to a new class of 2D materials with distinctive properties and significant potential for applications in advanced technologies. The transition metal (TM) elements can potentially be substituted with other TMs, adding the possibility of introducing new members to this emerging 2D family. In this regard, we propose three structural phases ($1H, 1T$, and $1T^{\prime }$) of $M{\mathrm{Si}}_2{\mathrm{N}}_4$ ($M=\mathrm{Ru}$ and Os) monolayers and examine their structural, vibrational, mechanical, electronic, and optical properties using ab initio methods. The results of cohesive energies ($E_{\mathrm{C}}$) indicate that the $1T^{\prime }$ structures are energetically more favorable than their $1H$ and $1T$ counterparts. The calculated phonon spectra reveal that the $M{\mathrm{Si}}_2{\mathrm{N}}_4$ nanosheets in distorted $1T^{\prime }$ phase are dynamically stable, while their $1H$ and $1T$ forms exhibit imaginary phonon modes, signifying vibrational instability of the systems. Ab initio molecular dynamics (AIMD) simulations also confirm that the $1T^{\prime }\text{−}M{\mathrm{Si}}_2{\mathrm{N}}_4$ structures remain thermally stable, even up to 600 K, without any notable structural deformations. The mechanical properties of $1T^{\prime }$ structures are assessed through the computation of in-plane stiffness ($Y_{2D}$), Poisson's ratio ($\nu$), and ultimate tensile strain (UTS). The intrinsic geometrical anisotropy of the $1T^{\prime }$ nanosheets induces strong orientation-dependent elastic properties, and the calculated large values of $Y_{2D}$ and high UTS indicate their rigidity and suitability for strain engineering of electronic and optical properties. The calculated electronic band structures reveal that, whereas unstable $1T\text{−}M{\mathrm{Si}}_2{\mathrm{N}}_4$ structures exhibit ferromagnetic metal properties, the stable $1T^{\prime }\text{−}{\mathrm{RuSi}}_2{\mathrm{N}}_4$ and $1T^{\prime }\text{−}{\mathrm{OsSi}}_2{\mathrm{N}}_4$ monolayers possess a nonmagnetic semiconducting ground state with indirect band gaps of 1.40 and 1.47 eV, respectively, at the level of the HSE functional. The observed shifts from metallic characteristics in the $1T$ phase to semiconducting nature in the $1T^{\prime }$ structures can be attributed to the Peierls distortion. Additionally, in accordance with the direct electronic bandgap of the $1T^{\prime }\text{−}M{\mathrm{Si}}_2{\mathrm{N}}_4$ crystals, strong optical absorption within the visible parts of the optical spectrum is estimated. Our study not only expands the family of 2D $MA{}_{2}Z{}_4$ crystals, but also introduces members with distinctive $1T^{\prime }$ geometries that exhibit promising mechanical, electronic, optical features for nanomechanical, optoelectronic, and green-energy applications.

Macroscopic sheets of hydrogen boride (HB) were fabricated by annealing microflakes, synthesized after the ion-exchange reaction. The sheets were centimeters wide and a micrometer thick. Handy and easy handling of the sheets has allowed us to conduct spectroscopic evaluations over various photon energy ranges. X-ray absorption spectra at the B K-shell absorption edge were obtained; the narrow spectral peaks were reproduced in theoretical simulations, revealing bonding characters between the H and B atoms. The macroscopic fabrication demonstrated in the present research offers a bottom-up approach toward real-world applications of these HB sheets.

We present an experimental investigation of the magnetic ground state in ${\mathrm{Ba}}_4{\mathrm{NbIr}}_3{\mathrm{O}}_{12}$, a fractional valent trimer iridate. X-ray absorption and photoemission spectroscopy show that the Ir valence lies between $3+$ and $4+$ while Nb is pentavalent. Combined dc/ac magnetization, specific heat, and muon spin rotation/relaxation ($\mu \mathrm{SR}$) measurements reveal no magnetic phase transition down to 0.05 K. Despite a significant Weiss temperature (${\mathrm{\Theta }}_{\mathrm{W}}\sim -15$ to $-25$ K) indicating antiferromagnetic correlations, a quantum spin-liquid (QSL) phase emerges and persists down to 0.1 K. This state likely arises from geometric frustration in the edge-sharing equilateral triangle Ir network. Our $\mu \mathrm{SR}$ analysis reveals a two-component depolarization, arising from the coexistence of rapidly (90%) and slowly (10%) fluctuating Ir moments. Powder x-ray diffraction and Ir-${\mathrm{L}}_3\mathrm{edge}$ x-ray absorption fine structure spectroscopy identify 8–10% Nb/Ir site-exchange, reducing frustration within part of the Ir network, and likely leading to the faster muon spin relaxation, while the structurally ordered Ir ions remain highly geometrically frustrated, giving rise to the rapidly spin-fluctuating QSL ground state. At low temperatures, the magnetic specific heat varies as $\gamma T+\alpha T^2$, indicating gapless spinon excitations, and possible Dirac QSL features with linear spinon dispersion, respectively.

The electrical 180° switching of the antiferromagnetic Néel vector is a long-term goal for building high-performance spintronic devices, such as the antiferromagnetic random-access memory that requires a single writing channel. For practical application, unavoidable thermal effects during the 180° Néel vector switching process should be taken into account, which still need a profound understanding. Here, we present an unconventional thermal-modulation spin-orbit torque (SOT) mechanism for the 180° Néel vector switching in the spin-splitting antiferromagnet $\mathrm{M}{\mathrm{n}}_5\mathrm{S}{\mathrm{i}}_3$, in which the electrical SOT switching is highly modulated by Joule heating. Guided by this mechanism, we observed two distinct switching dynamical behaviors during the switching process, depending on whether heating effects raise the temperature above the Néel temperature of $\mathrm{M}{\mathrm{n}}_5\mathrm{S}{\mathrm{i}}_3$ within the duration of electrical pulses. This unconventional switching mechanism is far beyond the scope of traditional SOT switching. Moreover, the thermal-modulation SOT mechanism showcases notably higher switching efficiency compared to the ferromagnetic and ferrimagnetic counterparts. Our findings not only deepen the understanding of the mechanism for electrical 180° switching of the Néel vector but also of spintronic devices based on spin-splitting antiferromagnets with low power consumption.

The influence of the presence of free electrons on the spectra of optical phonons and on electron-optical phonon scattering in quantum wells has been theoretically studied. As an example, calculations of the optical phonon spectra, intrasubband and intersubband electron-optical phonon scattering in 10-nm-GaAs quantum wells surrounded by ${\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ barriers were carried out at two temperatures of 77 and 300 K. It was shown that the frequency of intrasubband scattering varies nonmonotonically with increasing electron concentration in the quantum well. The relaxation rates of the wave vector and energy for scattering in the first and second subbands are found. It is shown that with increasing electron concentration in the quantum well, the frequency of intersubband scattering decreases.

Using advanced dynamical mean-field theory on a realistic level we study the normal-state correlated electronic structure of the high-pressure superconductor ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ and compare the features of the conventional bilayer (2222) Ruddelsden-Popper crystal structure with those of a newly identified monolayer-trilayer (1313) alternation. Both structural cases display Ni-$d_{z^2}$ flat-band character at low energy, which drives an electronic instability with a wave vector ${\mathbf{q}}_{\mathrm{I}}=(0.25,0.25,q_z)$ at ambient pressure, in line with recent experimental findings. The 1313 electronic structure exhibits significant layer selectivity, rendering especially the monolayer part to be Mott critical. At high pressure, this layer selectivity weakens and the 1313 fermiology displays arcs reminiscent to those of high-$T_c$ cuprates. In contrast to dominant intersite self-energy effects in the latter systems, here the Fermi arcs are the result of the multiorbital and multilayer interplay within a correlated flat-band scenario.