We provide a framework to theoretically describe long-range energy transfer in single and twisted two-dimensional hyperbolic slabs. We demonstrate that phonon polaritons, quantum superpositions of photons and lattice vib...We provide a framework to theoretically describe long-range energy transfer in single and twisted two-dimensional hyperbolic slabs. We demonstrate that phonon polaritons, quantum superpositions of photons and lattice vibrations in polar dielectrics, can mediate and enhance energy transfer at ranges far exceeding those of conventional mid-infrared (MIR) platforms and with extreme directionality. This is because the dipole-dipole interaction potential energy diverges along the asymptotes of the real-space hyperbolic opening angle. Our findings allow us to extend classical and quantum interactions between dipoles, typically strictly confined to the near-field, beyond several free-space MIR wavelengths. We use α-MoO as a representative material, but this mechanism could be extended to other anisotropic media beyond the MIR.
Interfacial exchange coupling plays a critical role in enabling novel phenomena in magnetic heterostructures, such as spin-triplet superconductivity, the quantum anomalous Hall effect, and advanced spintronic functionali...Interfacial exchange coupling plays a critical role in enabling novel phenomena in magnetic heterostructures, such as spin-triplet superconductivity, the quantum anomalous Hall effect, and advanced spintronic functionalities. While the microscopic characterization of this coupling is essential for elucidating the underlying mechanism, it remains technically challenging. Here, using spin-polarized scanning tunneling microscopy and quasiparticle interference, we directly observed interfacial exchange coupling in a magnetic tunnel junction formed by an Fe-coated tip and a Cr(001) surface. We found that the ferromagnetic tip induces a significant energy shift (up to 10 meV) in the spin-polarized surface state of Cr(001). This shift is highly sensitive to the tip-surface distance and the spin alignment between the Fe tip and the Cr surface, which can be switched by an external magnetic field. Our results demonstrate that extended 2D surface states can mediate strong exchange coupling across a heterojunction, enabling local control of interfacial exchange interaction-induced phenomena.
Magnetoelectric (ME) coupling in CMOS-compatible oxides would enable scalable, ultralow-power spintronic, neuromorphic and sensing devices. Here we report room-temperature ME coupling in transition-metal-doped HfZrO (HZO...Magnetoelectric (ME) coupling in CMOS-compatible oxides would enable scalable, ultralow-power spintronic, neuromorphic and sensing devices. Here we report room-temperature ME coupling in transition-metal-doped HfZrO (HZO) thin films. Structural analyses confirm a chemically homogeneous HZO matrix in which distinct polymorphs coexist, with uniform incorporation of the transition metal ions. The resulting films exhibit concurrently ferroelectricity and magnetism at room temperature, yielding a substantial magnetoelectric coupling, as corroborated by both macroscopic electrical measurements and microscopic piezoresponse force microscopy. This coupling is highly anisotropic, showing a positive response to in-plane magnetic fields and a weak negative response to out-of-plane fields, which can be explained by an interplay between positive magnetostriction and the unique negative piezoelectric coefficient of HZO. Our work establishes transition metal-doped HZO as a promising platform for single-material magnetoelectricity and opens a pathway for integrating multifunctional ME elements into silicon-compatible technologies.
Strong exciton-photon coupling can steer photophysical processes. However, the picture where it leads to two polaritonic states and a manifold of optically dark states is now questioned. Instead, a picture where inhomoge...Strong exciton-photon coupling can steer photophysical processes. However, the picture where it leads to two polaritonic states and a manifold of optically dark states is now questioned. Instead, a picture where inhomogeneous broadening results in a partial photonic contribution to the dark states has gained ground. To understand the consequence of these dark and so-called gray states, they first need to be experimentally quantified. Here we use angle-resolved emission, coupled to rate equation modeling, to quantify the absolute number of states in optical cavities. In addition, we also estimate the fraction of states that are gray by means of computer simulations. We find that the number of gray states is proportional to the overlap between the energy of the dark and polaritonic states. This knowledge can be applied to all previous and future studies to interpret how detuning affects the relative number of dark and gray states and, consequently, polaritonic dynamics.
Atomically thin transition metal dichalcogenides (TMDs) are promising platforms for quantum photonics owing to their ability to host strain-induced single-photon emitters (SPEs) that can be integrated with photonic nanos...Atomically thin transition metal dichalcogenides (TMDs) are promising platforms for quantum photonics owing to their ability to host strain-induced single-photon emitters (SPEs) that can be integrated with photonic nanostructures. However, the typically random polarization and near-isotropic emission of these emitters present challenges for controlled photon routing and photonic integration. Here, we demonstrate polarized and directional single-photon emission from WSe coupled to an all-dielectric nanoantenna supporting a quasi-bound state in the continuum (q-BIC). Relative to off-antenna emitters, antenna-coupled emitters exhibit similar linear polarization and modified far-field radiation patterns. Time-resolved photoluminescence measurements indicated an effective Purcell factor of ∼10, consistent with coupling to the q-BIC mode. Together, these results demonstrate that q-BIC nanoantennae provide an effective approach for engineering the polarization, emission direction, and radiative dynamics of TMD-based SPEs, offering a pathway toward engineered emitter-photon interfaces in integrated quantum photonic systems.
Central nervous system (CNS) diseases, including neurodegenerative disorders and brain cancers, remain leading causes of disability and death, largely due to limited drug penetration across the blood-brain barrier (BBB)....Central nervous system (CNS) diseases, including neurodegenerative disorders and brain cancers, remain leading causes of disability and death, largely due to limited drug penetration across the blood-brain barrier (BBB). Gold nanoparticles (AuNPs) have emerged as versatile platforms for CNS applications, with tunable morphology, surface chemistry, and optical properties, enabling both therapeutic and diagnostic use. This review highlights recent advances in the design and optimization of AuNPs for brain-targeted delivery, explores their applications in CNS diseases, and discusses current challenges, safety considerations, and future prospects for clinical translation.
Nanoparticle exsolution has emerged as an effective strategy for constructing catalytic structure, yet the precise control remains challenging. Here we introduce an "exsolution switch" strategy to regulate nanoparticle e...Nanoparticle exsolution has emerged as an effective strategy for constructing catalytic structure, yet the precise control remains challenging. Here we introduce an "exsolution switch" strategy to regulate nanoparticle exsolution by modulating the oxidation potential of oxide hosts. Ni is incorporated into CoMoO precursor to tune the oxidation potential and thereby control the exsolution behavior during a nitridation process. As Ni content increases, the nitride phase evolves from a homogeneous [NiCo]MoN solid solution to a [NiCo]MoN structure decorated with exsolved [NiCo]Mo nanoparticles ( = 0.05-0.20). The ammonia decomposition catalytic activities exhibit a volcano-shaped dependence on Ni contents, and the solid-solution [NiCo]MoN catalyst without nanoparticle exsolution delivers the highest activity with 19.2 mmol·g·min at 550 °C. Moderate Ni incorporation facilitates N-H bond cleavage for [NiCo]MoN structure, whereas excessive nanoparticle exsolution induces a shielding effect that inhibits N desorption. These findings provide a general strategy for controlling nanoparticle exsolution via chemical potential engineering.
Liu K, Sha Y, Yin B
… +20 more, Zhang H, Lu J, Liu S, Wu S, Ren Y, Guo Z, Gao J, Tian M, Wan N, Watanabe K, Taniguchi T, Tong B, Liu G, Lu L, Zhang Y, Luo W, Shi Z, Zhou S, Wu Q, Chen G
Graphene multilayers exhibit electronic spectra that depend sensitively on the layer number and stacking order. Here, we investigate ABCBC-stacked pentalayer graphene, a non-centrosymmetric mixed stacking that combines a...Graphene multilayers exhibit electronic spectra that depend sensitively on the layer number and stacking order. Here, we investigate ABCBC-stacked pentalayer graphene, a non-centrosymmetric mixed stacking that combines a rhombohedral trilayer-like cubic band and a Bernal bilayer-like parabolic band. Transport measurements reveal an intrinsic gap at charge neutrality that evolves strongly asymmetrically under a perpendicular displacement field, evidencing built-in layer polarization from broken inversion and mirror symmetry. By tuning the displacement field and carrier density, we drive multiple Lifshitz transitions and observe Landau levels with distinct degeneracies arising from the multi-flatband structure. Remarkably, a ν = -6 quantum Hall state emerges at an exceptionally low magnetic field of ∼20 mT. These results demonstrate that mixed-stacked multilayer graphene provides a tunable platform in which non-centrosymmetric symmetry breaking, multiple flatbands, and unusual quantum Hall physics coexist, opening opportunities to explore emergent correlated and topological electronic states.
Delivering proteins into subcellular compartments can significantly enhance their therapeutic potential. However, such delivery is largely restricted due to poor cell uptake and lysosomal trafficking/degradation of deliv...Delivering proteins into subcellular compartments can significantly enhance their therapeutic potential. However, such delivery is largely restricted due to poor cell uptake and lysosomal trafficking/degradation of delivered proteins. The direct membrane penetrating nanocarrier-based nonendocytic approach offers new opportunities for subcellular delivery of proteins. Here, we report histidine-terminated 2 nm gold nanoparticles as carriers for nucleus delivery of proteins via direct membrane penetration and temporary membrane pore formation while bypassing endosomal/lysosomal trafficking. It has been observed that successful nucleus delivery requires modular protein-carrier assembly of <50 nm size. Thus, nucleus delivery performance is sensitive to protein molecular weight and the ratio of protein to carrier concentration. Results show that nuclear delivery of proteins offers ∼2 times enhanced therapeutic performance as compared to their cytosolic delivery via the endocytic approach. The presented approach can be adapted to other therapeutic proteins and macromolecules for more efficient therapy.
Exchange bias (EB) in two-dimensional van der Waals (vdW) ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures holds great potential for advancing the applications of spintronic devices thanks to their defect-free...Exchange bias (EB) in two-dimensional van der Waals (vdW) ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures holds great potential for advancing the applications of spintronic devices thanks to their defect-free and atomically flat interfaces. Normally, a field-cooling process is needed to either trigger or sustain the EB effect. Here we report a sizable EB effect in the FeGaTe/CrSBr vdW heterostructure in a zero-field cooling process. Remarkably, an exceptionally large EB field () of 130.1 mT was achieved in FeGaTe/CrSBr at 5 K, even though the spin configuration in FeGaTe and CrSBr is orthogonally arranged. Additionally, the of FeGaTe/CrSBr exhibits pronounced nonmonotonic and asymmetric dependence on the cooling field, with the maximum values appearing at intermediate field strength. The EB is effectively tuned by the thickness of the FM layer relative to that of the AFM layer, identifying this ratio as an additional important governing parameter. Our work suggests an unconventional mechanism of EB in vdW heterostructures, providing an innovative route for fabricating low-power and robust 2D spintronic devices.
Low-dimensional hybrid metal halides (HMHs) are promising for next-generation optoelectronics due to their structural diversity and excellent photophysical properties. However, weak ionic interaction and electronic coupl...Low-dimensional hybrid metal halides (HMHs) are promising for next-generation optoelectronics due to their structural diversity and excellent photophysical properties. However, weak ionic interaction and electronic coupling between organic-inorganic moieties lead to structural instability and inferior carrier transport. Here, we report one-dimensional hybrid lead halide crystals using multidentate aminoazole molecules that form Pb-N coordination bonds at the organic-inorganic interface. This dual-side bonding locks the hybrid structure, hinders ion migration, and promotes charge transport through electronic orbital overlap. An X-ray detector based on ATDZPbBr polycrystalline wafers achieves the highest sensitivity of 1.63 × 10 μC Gy cm and an ultralow detection limit of 19.7 nGy s. This work establishes coordination chemistry as a powerful design paradigm for stable, high-performance hybrid semiconductors.
Zhou X, Gayduchenko I, Kudriashov A
… +12 more, Shein K, Kuksov A, Elesin L, Kravtsov M, Shilov A, Popova O, Jana S, Novoselov KS, Taniguchi T, Watanabe K, Goltsman G, Bandurin DA
Graphene Josephson junctions (JJs) are promising platforms for broadband quantum sensing because graphene combines frequency-independent absorption, ultralow electronic heat capacity, and weak electron-phonon coupling. W...Graphene Josephson junctions (JJs) are promising platforms for broadband quantum sensing because graphene combines frequency-independent absorption, ultralow electronic heat capacity, and weak electron-phonon coupling. While previous studies focused on microwave and infrared regimes, the terahertz (THz) range─where highly sensitive quantum detectors remain scarce─has largely remained unexplored. Here, we demonstrate a gate-tunable THz photoresponse in graphene JJs. Low-intensity THz illumination strongly suppresses the critical current, generating a pronounced photovoltage under current bias. From photovoltage measurements and independent electron thermometry, we extract a responsivity of 88 kV W and a noise-equivalent power of 45 aW Hz at 1.7 K. In addition, the hysteretic regime that persists up to 0.9 K suggests a possible route toward single-photon THz detection above millikelvin temperatures. Our results establish graphene JJs as promising candidates for cryogenic THz quantum sensing.
GHz-range surface acoustic waves (SAWs) are essential for high-frequency sensing, hybrid photonic-phononic, and quantum devices. However, SAW generation via interdigital transducers (IDTs) on piezoelectric substrates fac...GHz-range surface acoustic waves (SAWs) are essential for high-frequency sensing, hybrid photonic-phononic, and quantum devices. However, SAW generation via interdigital transducers (IDTs) on piezoelectric substrates faces significant scaling and attenuation challenges, besides being incompatible with silicon-based electronics due to the lack of piezoelectricity. Here, we demonstrate fundamental and higher-order SAW generation and detection in monolithic silicon using metallic transducers and time-resolved extreme ultraviolet diffraction measurements. Our results, supported by finite-element simulations, establish the equivalence of first- and second-order SAW frequencies (ν) and attenuation lifetimes (τ) over wide ranges spanning 3.5-16.5 GHz and 14-0.6 ns, respectively, that allow high-frequency SAW generation with large τ in the same device. We further show that τ is tunable via transducer geometry, achieving second-order SAWs (2ν) near 10 GHz with τ ≈ 5 ns. These findings reveal lower acoustic losses in silicon than those reported with IDTs on piezoelectric substrates.
Two-dimensional transition-metal dichalcogenides (TMDCs) are promising atomically thin semiconductors for next-generation electronics and optoelectronics. However, wafer-scale epitaxy of tungsten-based TMDCs is limited b...Two-dimensional transition-metal dichalcogenides (TMDCs) are promising atomically thin semiconductors for next-generation electronics and optoelectronics. However, wafer-scale epitaxy of tungsten-based TMDCs is limited by the chemical inactivity of conventional oxide precursors, which restricts the formation and incorporation of growth species. Here we introduce a solid-liquid-equilibrium molten precursor formed from mixed WO/NaWO that is proposed to generate reactive WO growth units and stabilize the tungsten supply. The resulting WS grows through sustained lateral propagation, producing crystallographically aligned monolayer wafers with narrow excitonic linewidths ascribed to suppressed disorder. First-principles calculations show that the molten precursor shifts the rate-limiting step from oxide conversion to edge incorporation, while sodium-mediated attachment lowers the propagation barrier. This work establishes precursor-state engineering as a general route to overcome reaction-limited regimes in tungsten-based two-dimensional TMDCs epitaxy.
Shortwave infrared (SWIR) imaging is widely employed in light detection and ranging, biomedical imaging, industrial inspection, and night vision. However, current InGaAs-based SWIR cameras remain expensive due to their c...Shortwave infrared (SWIR) imaging is widely employed in light detection and ranging, biomedical imaging, industrial inspection, and night vision. However, current InGaAs-based SWIR cameras remain expensive due to their complex fabrication and cooling requirements. Here, we report a cost-effective alternative using a standard silicon camera, augmented by upconversion from NaYF:Er@NaYF core-shell nanoparticles in a tunable, dual-resonance Fabry-Pérot cavity. A spatially varying cavity length allows spectral tunability, and the dual-resonance design enhances infrared absorption and visible emission simultaneously, resulting in up to 10-fold increase in upconversion intensity over a broad range of excitation wavelengths (1530-1570 nm). This enhancement enables imaging at 1550 nm with sub-10 μm spatial resolution, comparable to InGaAs-based systems, but at a significantly lower cost. We further demonstrate the potential of this platform for silicon wafer alignment and low-visibility imaging. This work introduces a scalable, cost-effective approach for SWIR imaging by leveraging mature silicon technologies and cavity-enhanced photon upconversion.
Tip-enhanced Raman spectroscopy (TERS) suffers from a trade-off between excitation efficiency and background interference, limiting the sensitivity and obscuring higher-order Raman transitions. To overcome this challenge...Tip-enhanced Raman spectroscopy (TERS) suffers from a trade-off between excitation efficiency and background interference, limiting the sensitivity and obscuring higher-order Raman transitions. To overcome this challenge, we introduce a chiral plasmonic fiber tip (CPFT) fabricated via fused tapering and rotational stretching that is internally excited by the fiber vector fundamental mode. By breaking the structural symmetry of the plasmonic fiber tip, the CPFT enables constructive interference of surface plasmon polaritons at the tip apex, producing a tip hotspot with enhanced electric-field intensity and gradient. This design not only amplifies the electromagnetic field but also suppresses far-field background noise, achieving a signal-to-noise ratio 4-fold higher than linearly polarized beam side excitation. Using the CPFT-based TERS platform, we visualized dark-state Raman modes including electric-quadrupole and magnetic-dipole transitions. This approach offers a strategy for high-contrast nanoscale spectroscopy, paving the way toward highly sensitive, low-noise, next-generation TERS systems.
Continuum-buried defect states in semiconductors are generally expected to be optically inactive because of their strong coupling to continuum bands. Here, we show that such defects can instead host radiative electronic...Continuum-buried defect states in semiconductors are generally expected to be optically inactive because of their strong coupling to continuum bands. Here, we show that such defects can instead host radiative electronic bound states in the continuum (BICs) using the silicon G center as a prototypical example. Hybrid functional first-principles calculations with a Hubbard correction reveal that a localized defect state, initially buried below the valence band maximum (VBM) in the ground state, undergoes exchange-driven energy-level reordering under optical excitation and shifts above the VBM. This exchange-induced transition suppresses nonradiative decay and enables a robust radiative emission. By computing temperature-dependent nonradiative lifetimes and comparing them to experimental photoluminescence (PL) lifetimes, we quantitatively reproduce the observed temperature dependence of the emission. These results uncover a stabilization mechanism for continuum-embedded defect states and establish electronic BICs as a general paradigm for designing defect-based optical systems, including quantum emitters and qubits.
Covalent organic frameworks (COFs) are promising photocatalysts, but improving their performance requires enhanced light harvesting and suppressed electron-hole recombination, often via postprotonation or conformational...Covalent organic frameworks (COFs) are promising photocatalysts, but improving their performance requires enhanced light harvesting and suppressed electron-hole recombination, often via postprotonation or conformational modulation. Here, using liquid-phase dark-field optical microscopy (DFM), we directly image in real time that the chloroacetic acid (MCA) interacts with COF-300 as a prototype COF host to form a highly protonated and twisted host-guest complex (MCA@COF-300) at the single-particle level, whereas acetic acid or trichloroacetic acid induces only weak effects. Further real-time single-particle photocatalytic imaging experiments show the high activity of MCA@COF-300. Combining ensemble characterizations and theoretical calculations, the coexistence of deep protonation and twist modulation in MCA@COF-300 is uncovered to favor visible light absorption and single-triplet intersystem crossing, leading to the formation of long-lived charge-separated states for boosting photocatalysis. Moreover, we apply the MCA@COF-300 photocatalyst to capture ultratrace radioactive I from an aqueous solution. These findings provide key insights into the photocatalysis of the COFs.
In van der Waals heterostructures hosting the quantum anomalous Hall (QAH) effect, an appropriate band alignment is often needed to prevent extrinsic electronic bands from obscuring the topological gap. However, band ali...In van der Waals heterostructures hosting the quantum anomalous Hall (QAH) effect, an appropriate band alignment is often needed to prevent extrinsic electronic bands from obscuring the topological gap. However, band alignment in two-dimensional heterostructures is typically regarded as a passive property determined by the material choice rather than an actively tunable degree of freedom. Here, we show that ferroelectric substrates provide a nonvolatile route to engineer band alignment through the surface electrostatic potential generated by ferroelectric polarization. The resulting surface potential shifts the energy levels of adjacent layers while largely preserving their intrinsic band dispersion, thereby enabling the controllable topological phase transitions. Using first-principles calculations, we demonstrate this mechanism in a van der Waals heterostructure composed of a fluorinated MoSe monolayer on a ferroelectric InS substrate. Polarization reversal drives a transition of band alignment from type-III to type-I, inducing a phase transition from metallic states to QAH insulating states with a finite topological gap.
Although energy level repulsion is typically observed in interacting quantum systems, non-Hermitian physics predicts the effect of level attraction, which occurs when significant energy dissipation is present. Here, we s...Although energy level repulsion is typically observed in interacting quantum systems, non-Hermitian physics predicts the effect of level attraction, which occurs when significant energy dissipation is present. Here, we show a manifestation of dissipative coupling in a high-quality AlGaAs-based polariton microcavity, where two polariton branches attract, resulting in an anomalous, inverted dispersion of the lower branch in momentum dispersion. The dissipative coupling is explained by the interaction with an indirect exciton, acting as a highly dissipative channel in our system. Using angle-resolved photoluminescence measurements we observe the evolution of the level attraction with exciton-photon detuning, leading to changes in anomalous dispersion shape within a single sample, and the observed dispersions are well captured within a phenomenological model. Our results present a new mechanism of dissipative coupling in light-matter systems and offer a tunable and well-controlled AlGaAs-based platform for engineering the non-Hermitian and negative mass effects in polariton systems.