Emergent charge order in pressurized kagome superconductor CsV3Sb5.

The discovery of several electronic orders in kagome superconductors AV3Sb5 (A means K, Rb, Cs) provides a promising platform for exploring unprecedented emergent physics1-9. Under moderate pressure (<2.2 GPa), the triple-Q charge density wave (CDW) order is monotonically suppressed by pressure, while the superconductivity shows a two-dome-like behaviour, suggesting an unusual interplay between superconductivity and CDW order10,11. Given that time-reversal symmetry breaking and electronic nematicity have been revealed inside the triple-Q CDW phase8,9,12,13, understanding this CDW order and its interplay with superconductivity becomes one of the core questions in AV3Sb5 (refs. 3,5,6). Here, we report the evolution of CDW and superconductivity with pressure in CsV3Sb5 by 51V nuclear magnetic resonance measurements. An emergent CDW phase, ascribed to a possible stripe-like CDW order with a unidirectional 4a0 modulation, is observed between Pc1 ≅ 0.58 GPa and Pc2 ≅ 2.0 GPa, which explains the two-dome-like superconducting behaviour under pressure. Furthermore, the nuclear spin-lattice relaxation measurement reveals evidence for pressure-independent charge fluctuations above the CDW transition temperature and unconventional superconducting pairing above Pc2. Our results not only shed new light on the interplay of superconductivity and CDW, but also reveal new electronic correlation effects in kagome superconductors AV3Sb5.

Charge-density-wave-driven electronic nematicity in a kagome superconductor.

Electronic nematicity, in which rotational symmetry is spontaneously broken by electronic degrees of freedom, has been demonstrated as a ubiquitous phenomenon in correlated quantum fluids including high-temperature superconductors and quantum Hall systems1,2. Notably, the electronic nematicity in high-temperature superconductors exhibits an intriguing entanglement with superconductivity, generating complicated superconducting pairing and intertwined electronic orders. Recently, an unusual competition between superconductivity and a charge-density-wave (CDW) order has been found in the AV3Sb5 (A = K, Rb, Cs) family with two-dimensional vanadium kagome nets3-8. Whether these phenomena involve electronic nematicity is still unknown. Here we report evidence for the existence of electronic nematicity in CsV3Sb5, using a combination of elastoresistance measurements, nuclear magnetic resonance (NMR) and scanning tunnelling microscopy/spectroscopy (STM/S). The temperature-dependent elastoresistance coefficient (m11 minus m12) and NMR spectra demonstrate that, besides a C2 structural distortion of the 2a0 × 2a0 supercell owing to out-of-plane modulation, considerable nematic fluctuations emerge immediately below the CDW transition (approximately 94 kelvin) and finally a nematic transition occurs below about 35 kelvin. The STM experiment directly visualizes the C2-structure-pinned long-range nematic order below the nematic transition temperature, suggesting a novel nematicity described by a three-state Potts model. Our findings indicate an intrinsic electronic nematicity in the normal state of CsV3Sb5, which sets a new paradigm for revealing the role of electronic nematicity on pairing mechanism in unconventional superconductors.

Room-Temperature Highly Efficient Nonvolatile Magnetization Switching by Current in van der Waals Fe3GaTe2 Devices.

The ability to manipulate magnetic states by a low electric current represents a fundamental desire in spintronics. In recent years, two-dimensional van der Waals (vdW) magnetic materials have attracted an extensive amount of attention due to their appreciable spin-orbit torque effect. However, for most known vdW ferromagnets, their relatively low Curie temperatures (TC) limit their applications. Consequently, low-power vdW spintronic devices that can operate at room temperature are in great demand. In this research, we fabricate nanodevices based on a solitary thin flake of vdW ferromagnet Fe3GaTe2, in which we successfully achieve nonvolatile and highly efficient magnetization switching by small currents at room temperature. Notably, the switching current density and the switching power dissipation are as low as 1.7 × 105 A/cm2 and 1.6 × 1013 W/m3, respectively, with an external magnetic field of 80 Oe; both are much reduced compared to those of conventional magnet/heavy metal heterostructure devices and other vdW devices.

Layer-Number-Dependent Magnetism in the Co-Doped van der Waals Ferromagnet Fe3GaTe2.

Recently, van der Waals (vdW) antiferromagnets have been proposed to be crucial for spintronics due to their favorable properties compared to ferromagnets, including robustness against magnetic perturbation and high frequencies of spin dynamics. High-performance and energy-efficient spin functionalities often depend on the current-driven manipulation and detection of spin states, highlighting the significance of two-dimensional metallic antiferromagnets, which have not been much explored due to the lack of suitable materials. Here, we report a new metallic vdW antiferromagnet obtained from the ferromagnet Fe3GaTe2 by cobalt (Co) doping. Through the layer-number-dependent Hall resistance and magnetoresistance measurements, an evident odd-even layer-number effect has been observed in its few-layered flakes, suggesting that it could host an A-type antiferromagnetic structure. This peculiar layer-number-dependent magnetism in Co-doped Fe3GaTe2 helps unravel the complex magnetic structures in such doped vdW magnets, and our finding will enrich material candidates and spin functionalities for spintronic applications.

Electrically Tunable, Rapid Spin-Orbit Torque Induced Modulation of Colossal Magnetoresistance in Mn3Si2Te6 Nanoflakes.

As a quasi-layered ferrimagnetic material, Mn3Si2Te6 nanoflakes exhibit magnetoresistance behavior that is fundamentally different from their bulk crystal counterparts. They offer three key properties crucial for spintronics. First, at least 106 times faster response compared to that exhibited by bulk crystals has been observed in current-controlled resistance and magnetoresistance. Second, ultralow current density is required for resistance modulation (∼5 A/cm2). Third, electrically gate-tunable magnetoresistance has been realized. Theoretical calculations reveal that the unique magnetoresistance behavior in the Mn3Si2Te6 nanoflakes arises from a magnetic field induced band gap shift across the Fermi level. The rapid current induced resistance variation is attributed to spin-orbit torque, an intrinsically ultrafast process (∼nanoseconds). This study suggests promising avenues for spintronic applications. In addition, it highlights Mn3Si2Te6 nanoflakes as a suitable platform for investigating the intriguing physics underlying chiral orbital moments, magnetic field induced band variation, and spin torque.

Monolayer atomic crystal molecular superlattices.

Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.

Layer-Dependent Magnetic Structure and Anomalous Hall Effect in the Magnetic Topological Insulator MnBi4Te7.

The intrinsic antiferromagnetic topological insulator (TI) MnBi4Te7 provides a capacious playground for the realization of topological quantum phenomena, such as the axion insulator states and quantum anomalous Hall (QAH) effect. In addition to nontrivial band topology, magnetism is another necessary ingredient for realizing these quantum phenomena. Here, we investigate signatures of thickness-dependent magnetism in exfoliated MnBi4Te7 thin flakes. We observe an obvious odd-even layer-number effect in few-layer MnBi4Te7. Noticeably, we show that in monolayer MnBi4Te7 the anomalous Hall effect exhibits a sign reversal. Compared with the case of MnBi2Te4, interlayer antiferromagnetic exchange coupling, which is essential for the realization of the QAH effect, is greatly suppressed in MnBi4Te7. The demonstration of thickness-dependent magnetic properties is helpful to further explore the topological quantum phenomena in MnBi4Te7.

A Membrane-Embedded Macromolecular Catalyst with Substrate Selectivity in Live Cells.

Substrate selectivity is one of the most attractive features of natural enzymes from their "bind-to-catalyze" working flow and is thus a goal for the development of synthetic enzyme mimics that mediate abiotic transformations. However, despite the recent success in the preparation of substrate-selective enzyme mimics based on single-chain nanoparticles, examples extending such selectivity into living systems have been absent. In this article, we report the in cellulo substrate selectivity of an enzyme-mimicking macromolecular catalyst based on a cationic dense-shell nanoparticle (DSNP) scaffold. With a systematic study on DSNP's structure-activity relationship, we demonstrate that the DSNP has excellent membrane affinity that is governed by several contributing factors, namely, charge density, type of charge, and particle size, and the best-performing phosphonium-rich DSNP can be used as a membrane-embedded catalyst (MEC) for efficient on-membrane synthesis. Importantly, the DSNP catalyst retains its selectivity toward lipophilic and anionic substrates when working as an MEC for on-membrane ligation. The usefulness of such substrate selectivity and on-membrane catalysis strategy was exemplified with several molecules of interest with low cell permeability and anionic nature, which were successfully transported into eukaryotic cells by after their formation directly on the cell membrane.

Record High 36 K Transition Temperature to the Superconducting State of Elemental Scandium at a Pressure of 260 GPa.

Elemental materials provide clean and fundamental platforms for studying superconductivity. However, the highest superconducting critical temperature (T_{c}) yet observed in elements has not exceeded 30 K. Discovering elemental superconductors with a higher T_{c} is one of the most fundamental and challenging tasks in condensed matter physics. In this study, by applying high pressure up to approximately 260 GPa, we demonstrate that the superconducting transition temperature of elemental scandium (Sc) can be increased to 36 K from the transport measurement, which is a record-high T_{c} for superconducting elements. The pressure dependence of T_{c} implies the occurrence of multiple phase transitions in Sc, which is in agreement with previous x-ray diffraction results. Optimization of T_{c} is achieved in the Sc-V phase, which can be attributed to the strong coupling between d electrons and moderate-frequency phonons, as suggested by our first-principles calculations. This study provides insights for exploring new high-T_{c} elemental metals.

Tunable Fluorescence and Morphology of Aggregates Built from a Mechanically Bonded Amphiphilic Bistable [2]Rotaxane.

Advanced Organic Chemical Materials Co-constructed Mechanically bonded amphiphiles (MBAs), also known as mechanically interlocked molecules (MIMs), have emerged as an important kind of functional building block for the construction of artificial molecular machines and soft materials. Herein, a novel MBA, i. e., bistable [2]rotaxane H2 was designed and synthesized. In the solution state, H2 demonstrated pH and metal ion-responsive emissions due to the presence of a distance-dependent photoinduced electron transfer (PET) process and the fluorescence resonance energy transfer (FRET) process, respectively. Importantly, the amphiphilic feature of H2 has endowed it with unique self-assembly capability, and nanospheres were obtained in a mixed H2 O/CH3 CN solvent. Moreover, the morphology of H2 aggregates can be tuned from nanospheres to vesicles due to the pH-controlled shuttling motion-induced alternation of H2 amphiphilicity. Interestingly, larger spheres with novel pearl-chain-like structures from H2 were observed after adding stoichiometric Zn2+ . In particular, H2 shows pH-responsive emissions in its aggregation state, allowing the visualization of the shuttling movement by just naked eyes. It is assumed that the well-designed [2]rotaxane, and particularly the proposed concept of MBA shown here, will further enrich the families of MIMs, offering prospects for synthesizing more MIMs with novel assembly capabilities and bottom-up building dynamic smart materials with unprecedented functions.

Layer-Number-Dependent Magnetism and Anomalous Hall Effect in van der Waals Ferromagnet Fe5GeTe2.

Realization of ferromagnetism in the two-dimensional (2D) van der Waals (vdW) crystals opens up a vital route to understand the magnetic ordering in the 2D limit and to design novel spintronics. Here, we report enriched layer-number-dependent magnetotransport properties in the vdW ferromagnet Fe5GeTe2. By studying the magnetoresistance and anomalous Hall effect (AHE) in nanoflakes with thicknesses down to monolayer, we demonstrate that while the bulk crystals exhibit soft ferromagnetism with an in-plane magnetic anisotropy, hard ferromagnetism develops upon thinning, and a perpendicular easy-axis anisotropy is realized in bilayer flakes, which is accompanied by a pronounced enhancement of AHE because of extrinsic mechanisms. For the monolayer flakes, the hard ferromagnetism is replaced by spin-glass-like behavior, in accordance with the localization effect in the 2D limit. Our results highlight the thickness-based tunability of the magnetotransport properties in the atomically thin vdW magnets that promises engineering of high-performance spintronic devices.

Potentiation of Vancomycin: Creating Cooperative Membrane Lysis through a "Derivatization-for-Sensitization" Approach.

Gram-negative bacteria, especially the ones with multidrug resistance, post dire challenges to antibiotic treatments due to the presence of the outer membrane (OM), which blocks the entry of many antibiotics. Current solutions for such permeability issues, namely lipophilic-cationic derivatization of antibiotics and sensitization with membrane-active agents, cannot effectively potentiate the large, globular, and hydrophilic antibiotics such as vancomycin, due to ineffective disruption of the OM. Here, we present our solution for high-degree OM binding of vancomycin via a hybrid "derivatization-for-sensitization" approach, which features a combination of LPS-targeting lipo-cationic modifications on vancomycin and OM disruption activity from a sensitizing adjuvant. 106- to 107-fold potentiation of vancomycin and 20-fold increase of the sensitizer's effectiveness were achieved with a combination of a vancomycin derivative and its sensitizer. Such potentiation is the result of direct membrane lysis through cooperative membrane binding for the sensitizer-antibiotic complex, which strongly promotes the uptake of vancomycin and adds to the extensive antiresistance effectiveness. The potential of such derivatization-for-sensitization approach was also supported by the combination's potent in vivo antimicrobial efficacy in mouse model studies, and the expanded application of such strategy on other antibiotics and sensitizer structures.

Flat-Band-Induced Anomalous Anisotropic Charge Transport and Orbital Magnetism in Kagome Metal CoSn.

For solids, the dispersionless flat band has long been recognized as an ideal platform for achieving intriguing quantum phases. However, experimental progress in revealing flat-band physics has so far been achieved mainly in artificially engineered systems represented as magic-angle twisted bilayer graphene. Here, we demonstrate the emergence of flat-band-dominated anomalous transport and magnetic behaviors in CoSn, a paramagnetic kagome-lattice compound. By combination of angle-resolved photoemission spectroscopy measurements and first-principles calculations, we reveal the existence of a kagome-lattice-derived flat band right around the Fermi level. Strikingly, the resistivity within the kagome lattice plane is more than one order of magnitude larger than the interplane one, in sharp contrast with conventional (quasi-) two-dimensional layered materials. Moreover, the magnetic susceptibility under the out-of-plane magnetic field is found to be much smaller as compared with the in-plane case, which is revealed to be arising from the introduction of a unique orbital diamagnetism. Systematic analyses reveal that these anomalous and giant anisotropies can be reasonably attributed to the unique properties of flat-band electrons, including large effective mass and self-localization of wave functions. Our results broaden the already fascinating flat-band physics, and demonstrate the feasibility of exploring them in natural solid-state materials in addition to artificial ones.

Pressure-Induced Dimensional Crossover in a Kagome Superconductor.

The recently discovered kagome superconductors AV_{3}Sb_{5} exhibit tantalizing high-pressure phase diagrams, in which a new domelike superconducting phase emerges under moderate pressure. However, its origin is as yet unknown. Here, we carried out the high-pressure electrical measurements up to 150 GPa, together with the high-pressure x-ray diffraction measurements and first-principles calculations on CsV_{3}Sb_{5}. We find the new superconducting phase to be rather robust and inherently linked to the interlayer Sb2-Sb2 interactions. The formation of Sb2-Sb2 bonds at high pressure tunes the system from two-dimensional to three-dimensional and pushes the p_{z} orbital of Sb2 upward across the Fermi level, resulting in enhanced density of states and increase of T_{C}. Our work demonstrates that the dimensional crossover at high pressure can induce a topological phase transition and is related to the abnormal high-pressure T_{C} evolution. Our findings should apply for other layered materials.

Superconductivity at 40 K in Lithiation-Processed [(Fe,Al)(OH)2][FeSe]1.2 with a Layered Structure.

Exploration of new superconductors has always been one of the research directions in condensed matter physics. We report here a new layered heterostructure of [(Fe,Al)(OH)2][FeSe]1.2, which is synthesized by the hydrothermal ion-exchange technique. The structure is suggested by a combination of X-ray powder diffraction and the electron diffraction (ED). [(Fe,Al)(OH)2][FeSe]1.2 is composed of the alternating stacking of a tetragonal FeSe layer and a hexagonal (Fe,Al)(OH)2 layer. In [(Fe,Al)(OH)2][FeSe]1.2, there exists a mismatch between the FeSe sublayer and the (Fe,Al)(OH)2 sublayer, and the lattice of the layered heterostructure is quasi-commensurate. The as-synthesized [(Fe,Al)(OH)2][FeSe]1.2 is nonsuperconducting due to the Fe vacancies in the FeSe layer. The superconductivity with a Tc of 40 K can be achieved after a lithiation process, which is due to the elimination of the Fe vacancies in the FeSe layer. The Tc is nearly the same as that of (Li,Fe)OHFeSe although the structure of [(Fe,Al)(OH)2][FeSe]1.2 is quite different from that of (Li,Fe)OHFeSe. The new layered heterostructure of [(Fe,Al)(OH)2][FeSe]1.2 contains an iron selenium tetragonal lattice interleaved with a hexagonal metal hydroxide lattice. These results indicate that the superconductivity is very robust for FeSe-based superconductors. It opens a path for exploring superconductivity in iron-base superconductors.

Programming DNA Tube Circumference by Tile Offset Connection.

DNA tubes with prescribed circumferences are appealing for numerous multidisciplinary applications. The DNA single-stranded tiles (SSTs) assembly method has demonstrated an unprecedented capability for programming the circumferences of DNA tubes in a modular fashion. Nevertheless, a distinct set of SSTs is typically required to assemble DNA tube of a specific circumference, with wider tubes requiring higher numbers of tiles of unique sequences, which not only increases the expense and design complexity but also hampers the assembly yield. Herein, we introduce "offset connection" to circumvent such challenges in conventional SST tube assembly. In this new connection scheme, the boundary SST tiles in an SST array are designed to connect in an offset manner. To compensate for the offset, the SST array has to grow wider until the array can close to form a wide tube with a tolerable degree of twist. Using this strategy, we have successfully assembled DNA tubes with prescribed circumferences consisting of 8, 12, 14, 16, 20, 24, 28, 32, 36, 42, 56, or 70 helices from two distinct sets of SSTs composed of 19×4 or 19×14 tiles.

Transition from Ferromagnetic Semiconductor to Ferromagnetic Metal with Enhanced Curie Temperature in Cr2Ge2Te6 via Organic Ion Intercalation.

Magnetism in the two-dimensional limit has become an intriguing topic for exploring new physical phenomena and potential applications. Especially, the two-dimensional magnetism is often associated with novel intrinsic spin fluctuations and versatile electronic structures, which provides vast opportunities in 2D material research. However, it is still challenging to verify candidate materials hosting two-dimensional magnetism, since the prototype systems have to be realized by using mechanical exfoliation or atomic layer deposition. Here, an alternative manipulation of two-dimensional magnetic properties via electrochemical intercalation of organic molecules is reported. Using tetrabutyl ammonium (TBA+), we synthesized a (TBA)Cr2Ge2Te6 hybrid superlattice with metallic behavior, and the Curie temperature is significantly increased from 67 K in pristine Cr2Ge2Te6 to 208 K in (TBA)Cr2Ge2Te6. Moreover, the magnetic easy axis changes from the ⟨001⟩ direction in Cr2Ge2Te6 to the ab-plane in (TBA)Cr2Ge2Te6. Theoretical calculations indicate that the drastic increase of the Curie temperature can be attributed to the change of magnetic coupling from a weak superexchange interaction in pristine Cr2Ge2Te6 to a strong double-exchange interaction in (TBA)Cr2Ge2Te6. These findings are the first demonstration of manipulation of magnetism in magnetic van der Waals materials by means of intercalating organic ions, which can serve as a convenient and efficient approach to explore versatile magnetic and electronic properties in van der Waals crystals.

Absence of van der Waals Gap in Ternary Thorium Nitride ThNF and ThNCl.

Two kinds of ternary thorium nitride compounds, ThNF and ThNCl, are synthesized. Via the refinement of X-ray diffraction patterns, the accurate crystal structure of the two compounds is solved. Although ThNF and ThNCl share a similar structure with MNX (M = Ti, Zr, Hf; X = Cl, Br) compounds, the interaction between adjacent ThNF and ThNCl layers is not a van der Waals gap. For ThNF, the strong electronegativity of F ions leads to the bonding of Th to the F both in the nearest neighbor layer and the next nearest neighbor layer, which results in the absence of a van der Waals gap between ThNF layers. However, for ThNCl, the reason for the absence of a van der Waals gap could be attributed to the large Th-Cl bond length due to the partially covalent Th-Cl bond as well as the flat ThN layer. It is the absence of van der Waals gap that results in the failure of intercalating cations into ThNF and ThNCl. Our result reveals the reason for unsuccessful intercalation in ThNF and ThNCl, thereby providing a deeper understanding for the interlayer interaction in ternary layer structures in metal nitride halides.

Proximity-Induced Superconductivity with Subgap Anomaly in Type II Weyl Semi-Metal WTe2.

Due to the nontrivial topological band structure in type II Weyl semi-metal tungsten ditelluride (WTe2), unconventional properties may emerge in its superconducting phase. While realizing intrinsic superconductivity has been challenging in the type II Weyl semi-metal WTe2, the proximity effect may open an avenue for the realization of superconductivity. Here, we report the observation of proximity-induced superconductivity with a long coherence length along the c axis in WTe2 thin flakes based on a WTe2/NbSe2 van der Waals heterostructure. Interestingly, we also observe anomalous oscillations of the differential resistance during the transition from the superconducting to the normal state. Theoretical calculations show excellent agreement with experimental results, revealing that such a subgap anomaly is the intrinsic property of WTe2 in superconducting state induced by the proximity effect. Our findings enrich the understanding of the superconducting phase of type II Weyl semi-metals and pave the way for their future applications in topological quantum computing.

Combination Cancer Therapy Using Chimeric Antigen Receptor-Engineered Natural Killer Cells as Drug Carriers.

The therapeutic limitations of conventional chemotherapeutic drugs include chemo-resistance, tumor recurrence, and metastasis. Numerous nanoparticle-based active targeting approaches have emerged to enhance the intracellular concentration of drugs in tumor cells; however, efficient delivery of these systems to the tumor site while sparing healthy tissue remains elusive. Recently, much attention has been given to human immune-cell-directed nanoparticle drug delivery, because immune cells can traffic to the tumor and inflammatory sites. Natural killer cells are a subset of cytotoxic lymphocytes that play critical roles in cancer immunosurveillance. Engineering of the human natural killer cell line, NK92, to express chimeric antigen receptors to redirect their antitumor specificity has shown significant promise. We demonstrate that the efficacy of chemotherapy can be enhanced in vitro and in vivo while reducing off-target toxicity by using chimeric antigen receptor-engineered NK92 cells as carriers to direct drug-loaded nanoparticles to the target site.