Energy Sciences

The tuning of the Fermi level in tin telluride, a topological crystalline insulator, is essential for accessing its unique surface states and optimizing its electronic properties for applications such as spintronics and quantum computing. In this study, we demonstrate that the Fermi level in tin telluride can be effectively modulated by controlling the tin concentration during chemical vapor deposition synthesis. By introducing tin-rich conditions, we observed a blue shift in the x-ray photoelectron spectroscopy core-level peaks of both tin and tellurium, indicating an upward shift in the Fermi level. This shift is corroborated by a decrease in work function values measured via ultraviolet photoelectron spectroscopy, confirming the suppression of Sn vacancies. Our findings provide a low-cost, scalable method to achieve tunable Fermi levels in tin telluride, offering a significant advancement in the development of materials with tailored electronic properties for next-generation technological applications.

Halides are promising solid-state electrolytes for all-solid-state lithium batteries due to their exceptional oxidation stability, high Li-ion conductivity, and mechanical deformability. However, their practicality is limited by the reliance on rare and expensive metals. This study investigates the Li2MgCl4 inverse spinel system as a cost-effective alternative. Molecular dynamics simulations reveal that lithium disordering at elevated temperatures significantly reduces the activation energy in Li2MgCl4. To stabilize this disorder at lower temperatures, we experimentally explored the Li x Zr1-x/2Mg x/2Cl4 system and found that Zr doping induces both Zr and Li disorder at the 16c site at room temperature (RT). This leads to a 2 order-of-magnitude increase in ionic conductivity for the Li1.25Zr0.375Mg0.625Cl4 composition, achieving 1.4 × 10-5 S cm-1 at RT, compared to pristine Li2MgCl4. By deconvoluting the role of lithium vacancies and dopants, we reveal that cation disordering to the 16c site predominantly enhances ionic conductivity, whereas lithium vacancy concentration has a very limited effect.

Heterogeneous materials containing molecular catalytic sites show promise for electrocatalytic reduction of CO2 to energy-enriched carbon products. Interactions between the catalyst and the heterogeneous support increasingly are recognized as important in governing product selectivity and rate. Recent work on Mn(R-bpy)(CO)3Br type catalysts immobilized on multiwalled carbon nanotubes (MWCNT) demonstrated control of electrocatalytic behavior with steric modification of the molecular catalyst. Phenyl groups installed in the 4,4 positions of the bipyridine ligand (ph-bpy) maximized performance through π-π interactions with the MWCNT support. Herein we report the outcome of extending the ligand π system with Mn(nap-bpy)(CO)3Br (nap-bpy = 4,4-di(naphthalen-1-yl)-2,2-bipyridine) and Mn(pyr-bpy)(CO)3Br (pyr-bpy = 4,4-di(pyren-1-yl)-2,2-bipyridine) immobilized on MWCNT. We demonstrate exceptional electrocatalysis with Mn(nap-bpy)(CO)3Br/MWCNT (FECO > 92%; JCO = 16.5 mA/cm2) and find that this catalyst electrochemically reduces bicarbonate in the absence of deliberately added CO2 at a remarkable overall selectivity of >80% for carbon products (FEHCOO- = 52% and FECO = 29%). We show diminishing returns to simply adding aromatic character to the bipyridyl ligand with Mn(pyr-bpy)(CO)3Br/MWCNT and observe a unique cambering of the Mn(nap-bpy)(CO)3Br bipyridyl ligand that we believe enables selective catalysis. Mechanistic studies were carried out on Mn(nap-bpy)(CO)3Br/MWCNT using a novel thin-film infrared spectroelectrochemical (IR-SEC) technique. These experiments observe the immobilized Mn(nap-bpy)(CO)3Br undergo single electron reduction to a Mn-centered radical that binds CO2 in a reduction-coupled process.

Through millions of years of evolution, bones have developed a complex and elegant hierarchical structure, utilizing tropocollagen and hydroxyapatite to attain an intricate balance between modulus, strength, and toughness. In this study, continuous fiber silk composites (CFSCs) of large size are prepared to mimic the hierarchical structure of natural bones, through the inheritance of the hierarchical structure of fiber silk and the integration with a polyester matrix. Due to the robust interface between the matrix and fiber silk, CFSCs show maintained stable long-term mechanical performance under wet conditions. During in vivo degradation, this material primarily undergoes host cell-mediated surface degradation, rather than bulk hydrolysis. We demonstrate significant capabilities of CFSCs in promoting vascularization and macrophage differentiation toward repair. A bone defect model further indicates the potential of CFSC for bone graft applications. Our belief is that the material family of CFSCs may promise a novel biomaterial strategy for yet to be achieved excellent regenerative implants.

Abstract: Forming heavily‐doped regions in 2D materials, like graphene, is a steppingstone to the design of emergent devices and heterostructures. Here, a selective‐area approach is presented to tune the work‐function and carrier density in monolayer graphene by spatially synthesizing sub‐monolayer gallium beneath the 2D‐solid. The localized metallic gallium is formed via precipitation from an underlying diamond‐like carbon (DLC) film that is spatially implanted with gallium‐ions. By controlling the interfacial precipitation process with annealing temperature, spatially precise ambipolar tuning of the graphene work‐function is achieved, and the tunning effect preserved upon cooling to ambient conditions. Consequently, charge carrier densities from ≈1.8 × 1010 cm−2 (hole‐doped) to ≈7 × 1013 cm−2 (electron‐doped) are realized, confirmed by in situ and ex situ measurements. The theoretical studies corroborated the role of gallium at the heterointerface on charge transfer and electrostatic doping of the graphene overlayer. Specifically, sub‐monolayer gallium facilitates heavy n‐doping in graphene. Extending this doping strategy to other implantable elements in DLC provides a new means of exploring the physics and chemistry of highly‐doped 2D materials.

The chirality of magnons, exhibiting left- and right-handed polarizations analogous to the counterparts of spin-up and spin-down, has emerged as a promising paradigm for information processing. However, the potential of this paradigm is constrained by the controllable excitation and transmission of chiral magnons. Here, the magnon transmission is explored in the Gd₃Fe₅O₁₂/NiO/Pt structures. It is demonstrated that both left- and right-handed magnon modes, thermally generated in the compensated ferrimagnet Gd₃Fe₅O₁₂, can efficiently propagate through the antiferromagnetic NiO layer. Remarkably, these modes undergo distinct decay processes in NiO, manifested by different evolutions of the spin diffusion length with temperature. This behavior can be explained by an exchange model rooted in the spin-flop magnetic configuration between Gd₃Fe₅O₁₂ and NiO, which establishes a chiral selection rule for magnon transmission. These findings offer significant fundamental insight into controlling chiral magnons, opening avenues for chirality-based magnonics.

Reducing decoherence in quantum computers rapidly decreases the overhead needed to construct a logical qubit from physical qubits. In solid-state systems, a class of defects known as two-level systems is a major source of decoherence. Currently, superconducting qubit experiments reduce dissipation due to the two-level systems by using large device dimensions. However, this approach only provides partial protection and results in a trade-off between qubit size and dissipation. In this work, we instead engineer the interactions between a qubit and the surrounding two-level systems using phononics. We fabricate a superconducting qubit on a phononic-bandgap metamaterial that suppresses phonon emission mediated by the two-level systems. The phonon-engineered bath of two-level systems shows increased lifetime and affects the thermalization dynamics of the qubit. Within the phononic bandgap, we observe the emergence of a non-Markovian qubit behaviour. Combined with qubit miniaturization, our approach could substantially extend the qubit relaxation times.