Nature Materials最新文献

The complex interaction of spin, valley and lattice degrees of freedom allows natural materials to create exotic topological phenomena. The interplay between topological wave materials and hydrodynamics could offer promising opportunities for visualizing topological physics and manipulating bioparticle unconventionally. Here we present topological acoustofluidic chips to illustrate the complex interaction between elastic valley spin and nonlinear fluid dynamics. We created valley streaming vortices and chiral swirling patterns for backward-immune particle transport. Using tracer particles, we observed arrays of clockwise and anticlockwise valley vortices due to an increase in elastic spin density. Moreover, we discovered exotic topological pressure wells in fluids, creating nanoscale trapping fields for manipulating DNA molecules. We also found a 93.2% modulation in the bandwidth of edge states, dependent on the orientation of the substrate’s crystallographic structure. Our study sets the stage for uncovering topological acoustofluidic phenomena and visualizing elastic valley spin, revealing the potential for topological-material applications in life sciences.

Excitons are fundamental excitations that govern the optical properties of semiconductors. Interactions between excitons can lead to various emergent phases of matter and large nonlinear optical responses. In most semiconductors, excitons interact via exchange interactions or phase-space filling. Correlated materials that host excitons coupled to other degrees of freedom could offer pathways for controlling these interactions. Here we demonstrate magnon-mediated interactions between excitons in CrSBr, an antiferromagnetic semiconductor. These interactions manifest as the dependence of the exciton energy on the exciton density via a magnonic adjustment of the spin canting angle. Our study demonstrates the emergence of quasiparticle-mediated interactions in correlated quantum materials, leading to large nonlinear optical responses and potential device concepts such as magnon-mediated quantum transducers.

Unidirectional magnetoresistance (UMR) in a bilayer heterostructure, consisting of a spin-source material and a magnetic layer, refers to a change in the longitudinal resistance on the reversal of magnetization and originates from the interaction of non-equilibrium spin accumulation and magnetization at the interface. Since the spin polarization of an electric-field-induced non-equilibrium spin accumulation in conventional spin-source materials is restricted to be in the film plane, the ensuing UMR can only respond to the in-plane component of magnetization. However, magnets with perpendicular magnetic anisotropy are highly desired for magnetic memory and spin-logic devices, whereas the electrical read-out of perpendicular magnetic anisotropy magnets through UMR is critically missing. Here we report the discovery of an unconventional UMR in the heterostructures of a topological semimetal (WTe₂) and a perpendicular magnetic anisotropy ferromagnetic insulator (Cr₂Ge₂Te₆), which allows to electrically read the up and down magnetic states of the Cr₂Ge₂Te₆ layer through longitudinal resistance measurements.

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.