Nature Materials最新文献

The stacking sequence of two-dimensional hexagonal boron nitride (hBN) is a critical factor that determines its polytypes and its distinct physical properties. Although most hBN layers adopt the thermodynamically stable AA′ stacking sequence, achieving alternative stacking configurations has remained a long-standing challenge. Here we demonstrate the scalable synthesis of hBN featuring unprecedented AA stacking, where atomic monolayers align along the c axis without any translation or rotation. This previously considered thermodynamically unfavourable hBN polytype is achieved through epitaxial growth on a two-inch single-crystalline gallium nitride wafer, using a metal–organic chemical vapour deposition technique. Comprehensive structural and optical characterizations, complemented by theoretical modelling, evidence the formation of AA-stacked multilayer hBN and reveal that hBN nucleation on the vicinal gallium nitride surface drives the unidirectional alignment of layers. Here electron doping plays a central role in stabilizing the AA stacking configuration. Our findings provide further insights into the scalable synthesis of engineered hBN polytypes, characterized by unique properties such as large optical nonlinearity.

The full-range, high-sensitivity and integratable detection of circularly polarized light (CPL) is critically important for quantum information processing, advanced imaging systems and optical sensing technologies. However, mainstream CPL detectors rely on chiral absorptive materials, and thus suffer from limited response wavelengths, low responsivity and poor discrimination ratios. Here we present a chiral light detector by utilizing valley materials to observe the spin angular momentum carried by chiral light. Delicately designed centrosymmetric metamaterials that can preserve the sign of optical spin angular momentum and greatly enhance its intensity in the near field are harnessed as a medium to inject polarized electrons into valley materials, which are then detected by the valley Hall effect. This enables high-sensitivity infrared CPL detection at room temperature by valleytronic transistors, and the detection wavelength is extended to the infrared. This approach opens pathways for chiral light detection and provides insights into potential applications of valleytronics in optoelectronic sensing.

Spin–orbit coupling (SOC) has played an important role in many topological and correlated electron materials. In graphene-based systems, SOC induced by a transition metal dichalcogenide at close proximity has been shown to drive topological states and strengthen superconductivity. However, in rhombohedral multilayer graphene, a robust platform for electron correlation and topology, superconductivity and the role of SOC remain largely unexplored. Here we report transport measurements of transition metal dichalcogenide-proximitized rhombohedral trilayer graphene. We observed a hole-doped superconducting state SC4 with a critical temperature of 234 mK. On the electron-doped side, we noted an isospin-symmetry-breaking three-quarter-metal phase and observed that the nearby weak superconducting state SC3 is substantially enhanced. Surprisingly, the original superconducting state SC1 in bare rhombohedral trilayer graphene is strongly suppressed in the presence of transition metal dichalcogenide—opposite to the effect of SOC on all other graphene superconductivities. Our observations form the basis of exploring superconductivity and non-Abelian quasiparticles in rhombohedral graphene devices.

Thermal transport across solid–solid interfaces is vital for advanced electronic and photonic applications, yet conventional conduction pathways often restrict performance. In polar crystals, hybridized vibrational modes called phonon polaritons offer a promising avenue to overcome the limitations of intrinsic phonon heat conduction. Here our work demonstrates that volume-confined hyperbolic phonon polariton (HPhP) modes can transfer energy across solid–solid interfaces at rates far exceeding phonon–phonon conduction. Using pump–probe thermoreflectance with a mid-infrared, tunable probe pulse with subpicosecond resolution, we remotely and selectively observe HPhP modes in hexagonal boron nitride (hBN) via broadband radiative heating from a gold source. Our measurements ascertain that hot electrons impinging at the interface radiate directly into the HPhPs of hBN in the near field, bypassing the phonon–phonon transport pathway. Such polaritonic coupling enables thermal transport speeds in solids orders of magnitude faster than possible through diffusive phonon processes. We thereby showcase a pronounced thermal transport enhancement across the gold–hBN interface via phonon–polariton coupling, advancing the limits of interfacial heat transfer.

The Pockels effect is essential for controlling optical signals at the highest speeds, particularly for electro-optic modulators in photonic integrated circuits. Lithium niobate (LN) and barium titanate (BTO) are two excellent Pockels materials to this end. Here we measure the Pockels coefficients and permittivity in LN and BTO over a continuous frequency range from 100 MHz to 330 GHz. These properties are constant across this frequency range in LN, but have a strong frequency dependence in BTO. Still, our measurements show that BTO has remarkable electro-optic properties compared with LN. Furthermore, we show how BTO devices can be designed with a flat electro-optic frequency response despite the Pockels coefficient dispersion. Finally, we expound our method for broadband characterization of these vital electro-optic properties, utilizing specialized integrated electro-optic phase shifters. Altogether, this work empowers the design of high-speed BTO devices and the development of new electro-optic materials.

Solid-state thermoelectric technology presents a compelling solution for converting waste heat into electrical energy. However, its widespread application is hindered by long-term stability issues, particularly at the electrode–thermoelectric material interface. Here we address this challenge by constructing an atomic-scale direct bonding interface. By forming robust chemical bonds between Co and Sb atoms, we develop MgAgSb/Co thermoelectric junctions with a low interfacial resistivity (2.5 µΩ cm²), high bonding strength (60.6 MPa) and high thermal stability at 573 K. This thermally stable and ohmic contact interface enables MgAgSb-based thermoelectric modules to achieve a conversion efficiency of 10.2% at a temperature difference of 287 K and to exhibit negligible degradation over 1,440 h of thermal cycling. Our findings underscore the critical role of atomic-scale interface engineering in advancing thermoelectric semiconductor devices, enabling more efficient and durable thermoelectric modules.

Cell competition is a tissue surveillance mechanism for eliminating unwanted cells, being indispensable in development, infection and tumourigenesis. Although studies have established the role of biochemical mechanisms in this process, due to challenges in measuring forces in these systems, how mechanical forces determine the competition outcome remains unclear. Here we report a form of cell competition that is regulated by differences in force transmission capabilities, selecting for cell types with stronger intercellular adhesion. Direct force measurements in ex vivo tissues and different cell lines reveal that there is an increased mechanical activity at the interface between two competing cell types, which can lead to large stress fluctuations resulting in upward forces and cell elimination. We show how a winning cell type endowed with a stronger intercellular adhesion exhibits higher resistance to elimination and benefiting from efficient force transmission to the neighbouring cells. This cell elimination mechanism could have broad implications for keeping the strong force transmission ability for maintaining tissue boundaries and cell invasion pathology.

Bioinspired materials based on self-assembling peptides are promising for tackling various challenges in biomedical engineering. While contemporary data-driven approaches have led to the discovery of self-assembling peptides with various structures and properties, predicting the functionalities of these materials is still challenging. Here we describe the deep learning-guided de novo design of antimicrobial materials based on self-assembling peptides targeting bacterial membranes to address the emerging problem of bacterial drug resistance. Our approach integrates non-natural amino acids for enhanced peptide self-assembly and effectively predicts the functional activity of the self-assembling peptide materials with minimal experimental annotation. The designed self-assembling peptide leader displays excellent in vivo therapeutic efficacy against intestinal bacterial infection in mice. Moreover, it exhibits an enhanced biofilm eradication capability and does not induce acquired drug resistance. Mechanistic studies reveal that the designed peptide can self-assemble on bacterial membranes to form nanofibrous structures for killing multidrug-resistant bacteria. This work thus provides a strategy to discover functional peptide materials by customized design.

Antiferromagnetic Heisenberg chains exhibit two distinct types of excitation spectrum: gapped for integer-spin chains and gapless for half-integer-spin chains. However, in finite-length half-integer-spin chains, quantization induces a gap, requiring precise control over sufficiently long chains to study its evolution. Here we create length-controlled spin-1/2 Heisenberg chains by covalently linking Olympicenes—Olympic-ring-shaped magnetic nanographenes. With large exchange interactions, tunable lengths and negligible magnetic anisotropy, this system is ideal for investigating length-dependent spin excitations, probed via inelastic electron tunnelling spectroscopy. We observe a power-law decay of the lowest excitation energy with length L, following a 1/L dependence in the large-L regime, consistent with theory. For L = 50, a V-shaped excitation continuum confirms a gapless behaviour in the thermodynamic limit. Additionally, low-bias current maps reveal the standing wave of a single spinon in odd-numbered chains. Our findings provide evidence for the realization of a one-dimensional analogue of a gapless spin liquid within an artificial graphene lattice.