Superconductivity in Quasi-One-Dimensional Ferromagnet CrSbSe3 under High Pressure.

Nearly a decade has passed since the discovery of superconductivity in CrAs, but until now, the discovered structure types of chromium-based superconductors are still scanty. It is urgent to expand this family to decipher the interplay between magnetism and superconductivity penetratingly. Here, we report the observation of superconductivity in ferromagnet CrSbSe3 with a quasi-one-dimensional structure under high pressure. Under compression, CrSbSe3 undergoes an insulator-to-metal transition and sequential isostructural phase transitions accompanied by volume collapse. Superconductivity emerges at 32.8 GPa concomitant with metallization in CrSbSe3. A maximum superconducting transition temperature Tc of 7.7 K is achieved at 57.9 GPa benefiting from both the phonon softening and the enhanced p-d hybridization between Se and Cr in CrSbSe3. The discovery of superconductivity in CrSbSe3 expands the existing chromium-based superconductor family and sheds light on the search for concealed superconductivity in low-dimensional van der Waals materials.

Pressure-Driven Polymorphic Transition, Emergent Insulator-To-Metal Transition, and Photoconductivity Switching in Violet Phosphorus.

Polymorphic phase transition is an essential phenomenon in condensed matter that the physical properties of materials may undergo significant changes due to the structural transformation. Phase transition has thus become an important means and dimension for regulating material properties. Herein, this study demonstrates the pressure-induced multi-transition of both structure and physical properties in violet phosphorus, a novel phosphorus allotrope. Under compression, violet phosphorus undergoes sequential polymorphic phase transitions. Concomitant with the first phase transition, violet phosphorus exhibits emergent insulator-metal transition, superconductivity, and dramatic switching from positive to negative photoconductivity. Remarkably, the resistance of violet phosphorus shows a sudden drop of around 107 along with the phase transition. In addition, piezochromism from translucent red to opaque black and suppression of photoluminescence are observed upon compression. Of particular interest is that the sample irreversibly transforms into black phosphorus with a pronounced discrepancy in physical properties from the pristine violet phosphorus after decompression. The abundant polymorphic transitions and property changes in violet phosphorus have significant implications for designing novel pressure-responsive electronic/optoelectronic devices and exploring concealed polymorphic transition materials.

Pressure-Induced Structural Phase Transition, Anomalous Insulator-to-Metal Transition, and n-p Conduction-Type Switching in Defective, NiAs-Type Cr1-δTe.

Cr1-δTe, as a unique series of defective compounds with a NiAs-type structure and periodic metal vacancies, has attracted intensive research interest because of its diversity in structure and property dependent on the tunable stoichiometric ratio. Another feature of these compounds is their ability to switch between NiAs- and MnP-type structures, in which there often exist composition-, temperature-, or pressure-induced phase transitions accompanied by intriguing physical property switching. Herein, we report the syntheses of a series of Cr1-δTe compounds with similar compositions but distinct crystal structures, their phase transitions, anomalous transport, and photoelectric conduction behaviors under high pressure (HP). For the three Cr1-δTe compounds with δ = 0, 0.25, 0.375, CrTe undergoes pressure-induced NiAs-to-MnP phase transition at around 15 GPa, while Cr3Te4 and Cr5Te8 undergo isostructural phase transitions at around 12 and 11 GPa, respectively. Electrical transport measurements indicate anomalous conduction behaviors: CrTe undergoes a semiconductor-to-metal transition at around 24 GPa, while Cr3Te4 and Cr5Te8 show unexpected metal-semiconductor-metal transitions sequentially upon compression. Besides, CrTe and Cr5Te8 exhibit pressure-induced n-p conduction-type switching at around 9 and 3 GPa, respectively, while Cr3Te4 shows p-type conductivity in the full pressure range. Local structure analyses based on in situ HP Raman spectra are performed to understand the structure and property evolutions of Cr1-δTe under HP. Defective transition-metal chalcogenides with pressure-induced NiAs-to-MnP phase transition and conduction-type conversion provide a potential platform for the rational design of photoelectric conversion devices.

Diverse Thermal Expansion Behaviors in Ferromagnetic Cr1-δTe with NiAs-Type, Defective Structures.

Negative thermal expansion (NTE) and zero thermal expansion (ZTE) properties are of great significance for the long-life stable operation of precision equipment. However, there are still existing challenges in finding new materials that exhibit NTE or ZTE over a wide temperature range. Here, we report negative, zero, and positive thermal expansion in NiAs-type, defective Cr1-δTe, containing three compounds: hexagonal CrTe, monoclinic Cr3Te4, and trigonal Cr5Te8. CrTe shows the NTE behavior from 280 to 340 K with the volume coefficient of thermal expansion αV = -27.6 × 10-6 K-1. Cr3Te4 shows the ZTE behavior over a wide temperature range of 180-320 K (αV = 0.16 × 10-6 K-1). And Cr5Te8 holds the PTE behavior over the whole temperature range (αV = 38.5 × 10-6 K-1). All of the samples show obvious anisotropic thermal expansion on heating. Combined with the magnetic measurements, it can be confirmed that the NTE and ZTE properties in ferromagnetic Cr1-δTe originate from the magnetovolume effect (MVE). Such NiAs-type, defective compounds with similar compositions but different structures provide a new perspective for tuning the NTE properties of materials and searching for new materials with ZTE over a wide temperature range.

Influence of Barium Intercalated Ions on Magnetic Interaction in the Tellurate Compound BaNi2TeO6.

A novel transition metal tellurate single-crystal BaNi2TeO6 with layered honeycomb lattices has been successfully synthesized. The crystal structure of BaNi2TeO6 reveals that there are the Ni2+ honeycomb lattice layers and Te6+ triangle lattice layers in the ab plane. BaNi2TeO6 shows an antiferromagnetic (AFM) transition at ∼25 K, which is almost the same temperature as the Curie-Weiss temperature θ ∼ -27 K, indicating the presence of the AFM interactions without obvious magnetic frustration in the system. However, the field-induced successive magnetic transitions observed at Hc1 ∼ 16.2 T and Hc2 ∼ 42.2 T show the complicated spin structure in BaNi2TeO6. Compared with the isostructural Na2Ni2TeO6, the various magnetic properties indicate that the intercalated ions (Ba2+) can significantly affect the magnetic properties of the layered honeycomb lattices, which may be useful for exploring the spin-liquid state and valence bond liquid state in the layered honeycomb lattice compounds.

Pressure-Driven Two-Step Second-Harmonic-Generation Switching in BiOIO3.

Materials with multi-stabilities controllable by external stimuli have potential for high-capacity information storage and switch devices. Herein, we report the observation of pressure-driven two-step second-harmonic-generation (SHG) switching in polar BiOIO3 for the first time. Structure analyses reveal two pressure-induced phase transitions in BiOIO3 from the ambient noncentrosymmetric phase (SHG-high) to an intermediate noncentrosymmetric phase (SHG-intermediate) and then to a centrosymmetric phase (SHG-off). The three-state SHG switching was inspected by in situ high-pressure powder SHG and polarization-dependent single-crystal SHG measurements. Local structure analyses based on the in situ Raman spectra and X-ray absorption spectra reveal that the SHG switching is caused by the step-wise suppression of lone-pair electrons on the [IO3 ]- units. The dramatic evolution of the functional units under compression also leads to subtle changes of the optical absorption edge of BiOIO3 . Materials with switchable multi-stabilities provide a state-of-art platform for next-generation switch and information storage devices.

Controllable Syntheses, Crystal Structure Evolution, and Photoluminescence of Polymorphic Zirconium Oxyfluorides.

Precise synthesis of polymorphic phases with similar components but distinct crystal structures is one of the key problems in inorganic chemistry. In this work, we report a fluorination method adopting ZrO2 as the starting material and NH4F as the fluoridation agent that can afford multiphases in the Zr-O-F system, including Zr7O9F10, Zr3O2F8, ZrO0.46F3.08, ZrO0.33F3.33, ß-ZrF4, NH4Zr2F9, and NH4ZrF5. A preliminary phase formation diagram was established as a function of the fluorination temperature (T), reaction time (t), and F/Zr ratio after systematic optimization of the preparation conditions. Among the as-obtained phases, the detailed crystal structures of Zr7O9F10 and ZrO0.33F3.33 were refined based on the powder X-ray diffraction patterns. As the F/O ratio increases, the crystal structures of Zr-O-F phases transform gradually from an anion-deficient α-UO3-related structure of Zr7O9F10 to an anion-excess ReO3-related structure of ZrO0.33F3.33. At last, we also prepared Ti-doped ZrO2, Zr7O9F10, ZrO0.46F3.08, and ZrO0.33F3.33 to study the host-lattice-dependent photoluminescence properties of zirconium oxyfluorides. The four materials show distinct photoluminescence in the UV and visible regions due to different local coordination environments of Zr/Ti. This work demonstrates the low-temperature fluorination method as an efficient route to phase-selective polymorphic metal oxyfluorides, which can be employed in further structure-property relationship studies.

Na3Bi(IO3)6: An Alkali-Metal Bismuth Iodate with Intriguing One-Dimensional [BiI6O18] Chains and Pressure-Induced Structural Transition.

An alkali-metal bismuth iodate, Na3Bi(IO3)6, was successfully obtained by the hydrothermal method for the first time and contains intriguing one-dimensional [BiI6O18] chains. High-pressure Raman spectra were carried out to investigate the structural transition of Na3Bi(IO3)6. Electronic states and anisotropic optical responses were also investigated by theoretical calculations.

Designing Three Fluorooxoborates with a Wide Transmittance Window by Anionic Group Substitution.

Three fluorooxoborates, K0.42Rb2.58B3O3F6 and M3B2PO5F4 (M = K, Cs), were designed and synthesized under the open system. One of the common features is that the title compounds consist of six-membered oxofluoride anions. The oxofluoride anions [B3O3F6]3- and [B2PO5F4]3- display structures similar to the boroxine [B3O6]3-. Anionic group substitution using the [BO2F2]3- and [PO4]3- units can improve the optical property of the [B3O6]3- anion and help to generate a wide transmittance window.

Hsa_circ_0057104, by competitive adsorption of miR-627-5p, mediates CCND2 expression to promote malignant proliferation and Warburg effect of colorectal cancer.

OBJECTIVE: hsa_circ_0057104 (circPDK1) has been elucidated to regulate malignant behavior in pancreatic and renal cell carcinoma. The study functionally aimed at how circPDK1 modifies colorectal cancer (CRC) progression, along with its potential molecular mechanism. METHODS: circPDK1 expression patterns in CRC tissues and cell lines were analyzed by RT-qPCR. circPDK1/miR-627-5p/CCND2 expression levels were changed by transient transfection. CCK-8 assay, flow cytometry, Transwell, immunoblotting, and commercial kits were utilized to measure CRC cell proliferation, apoptosis, invasion/migration, and glycolysis processes. Dual luciferase reporting assay and RIP assay were employed to evaluate the targeting relationship between circPDK1/miR-627-5p/CCND2. RESULTS: circPDK1 was highly expressed in CRC. circPDK1 knockdown inhibited CRC cell proliferation, invasion/migration, and warburg effect and forced apoptosis. Overexpressing circPDK1 had the opposite effect. The effects of circPDK1 knockdown or circPDK1 overexpression on CRC cells were mitigated by downregulating miR-627-5p or CCND2, respectively. CircPDK1, by competitive adsorption of miR-627-5p, mediated CCND2 expression. CONCLUSION: CircPDK1 induces the malignant behavior of CRC by competitive adsorption of miR-627-5p mediating CCND2 expression, offering new insights into the future development of CRC-targeted drugs.

Transient Magnetoelectric Coupling Induced by the Dynamic Intertwinement between Exchange Striction and Compensation in GdFeO3.

In this study, we investigate the dynamic magnetoelectric (ME) coupling behaviors of GdFeO3 under pulsed magnetic fields. When a magnetic field is applied along the c-axis, and the temperature is near the compensation temperature (Tcomp = 3.5 K), we observe a subtle transition involving the reversal of Fe3+ moments at approximately 0.8 T in magnetization (M) measurements. This transition induces a corresponding jump in electrical polarization (P), which is not present in the static field measurements. The dynamic intertwining between M and P signifies a competition between antiferromagnetic (AFM) coupling between Gd3+ and Fe3+ moments and their Zeeman energies. The robust AFM coupling leads to the reversal of Fe3+ moments near Tcomp, triggering the abrupt change in P. Based on the exchange striction mechanism in the ferrimagnetic GdFeO3, we propose the possibility of achieving highly magnetic field sensitive ME coupling near the compensation temperature in ferrimagnetic multiferroic orthoferrites.

Unexpected giant negative area compressibility in palladium diselenide.

Negative area compressibility (NAC) is a counterintuitive 'squeeze-expand' behavior in solids that is very rare but attractive due to possible pressure-response applications and coupling with rich physicochemical properties. Herein, NAC behavior is reported in palladium diselenide with a large magnitude and wide pressure range. We discover that, apart from the rigid flattening of layers that has been generally recognized, the unexpected giant NAC effect in PdSe2 largely comes from anomalous elongation of intralayer chemical bonds. Both structural variations are driven by intralayer-to-interlayer charge transfer with enhanced interlayer interactions under pressure. Our work updates the mechanical understanding of this anomaly and establishes a new guideline to explore novel compression-induced properties.

Manipulation of nonlinear optical responses in layered ferroelectric niobium oxide dihalides.

Realization of highly tunable second-order nonlinear optical responses, e.g., second-harmonic generation and bulk photovoltaic effect, is critical for developing modern optical and optoelectronic devices. Recently, the van der Waals niobium oxide dihalides are discovered to exhibit unusually large second-harmonic generation. However, the physical origin and possible tunability of nonlinear optical responses in these materials remain to be unclear. In this article, we reveal that the large second-harmonic generation in NbOX2 (X = Cl, Br, and I) may be partially contributed by the large band nesting effect in different Brillouin zone. Interestingly, the NbOCl2 can exhibit dramatically different strain-dependent bulk photovoltaic effect under different polarized light, originating from the light-polarization-dependent orbital transitions. Importantly, we achieve a reversible ferroelectric-to-antiferroelectric phase transition in NbOCl2 and a reversible ferroelectric-to-paraelectric phase transition in NbOI2 under a certain region of external pressure, accompanied by the greatly tunable nonlinear optical responses but with different microscopic mechanisms. Our study establishes the interesting external-field tunability of NbOX2 for nonlinear optical device applications.

Do governmental policy interventions help urban economic recovery? Experimental evidence from China's provinces governance amid the COVID-19 pandemic.

By examining China's province-level data, this paper uses governmental intervention theory to investigate the extent to which governmental policy interventions alleviate the impact of the COVID-19 pandemic on local economic growth. Results suggest that stronger government intervention during COVID-19 pandemic boost the economic recovery, and the effectiveness of governmental policy interventions is contingent on pandemic severity and local economic endowment. Specifically, facilitating effect of government intervention on economic growth is effective in all provinces, and the impact of government intervention is more pronounced in the province with more diagnosed cases, a high level of marketization and fiscal income.

High-Magnetic-Sensitivity Magnetoelectric Coupling Origins in a Combination of Anisotropy and Exchange Striction.

Magnetoelectric (ME) coupling is highly desirable for sensors and memory devices. Herein, the polarization (P) and magnetization (M) of the DyFeO3 single crystal were measured in pulsed magnetic fields, in which the ME behavior is modulated by multi-magnetic order parameters and has high magnetic-field sensitivity. Below the ordering temperature of the Dy3+-sublattice, when the magnetic field is along the c-axis, the P (corresponding to a large critical field of 3 T) is generated due to the exchange striction mechanism. Interestingly, when the magnetic field is in the ab-plane, ME coupling with smaller critical fields of 0.8 T (a-axis) and 0.5 T (b-axis) is triggered. We assume that the high magnetic-field sensitivity results from the combination of the magnetic anisotropy of the Dy3+ spin and the exchange striction between the Fe3+ and Dy3+ spins. This work may help to search for single-phase multiferroic materials with high magnetic-field sensitivity.

Pressure-Induced Phase Transition, Jahn-Teller Suppression, Optical and Electronic Property Evolutions in Ruddlesden-Popper Perovskites Rb2 CuCl4-x Brx.

Transition-metal containing halides with Ruddlesden-Popper (RP) perovskite structures have received extensive attention owing to their emerging and anisotropic photoelectric functionalities. Among them, A2 CuX4 (A=alkali metal or organic cations, X=Cl, Br, I) series are particular, because of the Jahn-Teller distortion of Cu2+ sensitive to external stimuli such as temperature and pressure. In this article, we report the structure evolution and physical property responses of RP perovskites Rb2 CuCl4-x Brx (x=1, 2) to external pressure. Dramatic structural phase transitions from orthorhombic to monoclinic occur around 3.0 GPa in both materials regardless of their distinct compositions. Structure analyses reveal the suppression and final vanishing of the Jahn-Teller distortion of Cu2+ cations under compression and crossing the phase transition, respectively. Rb2 CuCl4-x Brx perovskites exhibit abrupt bandgap narrowing (from reddish-brown to black) along with the structural phase transition, and an overall bandgap narrowing of 75% up to ∼27 GPa but still keeping semiconductive. During the compression processes, the resistances of Rb2 CuCl4-x Brx have been greatly reduced by 5-orders of magnitude. Moreover, all of the pressure-induced phenomena in Rb2 CuCl4-x Brx perovskites are reversible upon decompression and no obvious difference is observed for the pressure responses between [CuCl4 Br2 ] and [CuCl4 (Cl,Br)2 ] coordination environments. The impact of pressure on the structural and physical properties in two-dimensional Rb2 CuCl4-x Brx provides in-depth understanding on the structure design of functional halide perovskites at ambient conditions.

Pressure-Driven Sequential Lattice Collapse and Magnetic Collapse in Transition-Metal-Intercalated Compounds FexNbS2.

Volume collapse under high pressure is an intriguing phenomenon involving subtle interplay between lattice, spin, and charge. The two most important causes of volume collapse are lattice collapse (low-density to high-density) and magnetic collapse (high-spin to low-spin). Herein we report the pressure-driven sequential volume collapses in partially intercalated FexNbS2 (x = 1/4, 1/3, 1/2, 2/3). Because of the distinct interlayer atomic occupancy, the low-iron-content samples exhibit both lattice and magnetic collapses under compression, whereas the high-iron-content samples exhibit only one magnetic collapse. Theoretical calculations indicate that the low-pressure volume collapses for x = 1/4 and x = 1/3 are lattice collapses, and the high-pressure volume collapses for all four samples are magnetic collapses. The magnetic collapse involving the high-spin to low-spin crossover of Fe2+ has also been verified by in situ X-ray emission measurements. Integrating two distinct volume collapses into one material provides a rare playground of lattice, spin, and charge.

Site-Specific Pressure-Driven Spin-Crossover in Lu1-xScxFeO3.

Pressure-driven spin-crossover (PSCO) is a collective quantum phenomenon frequently observed in transition-metal-based systems. According to the crystal-field theory, PSCO highly depends on the surrounding coordination environment of a given magnetic ion; nevertheless, it has never been verified experimentally up to now. Herein, we report the observation of a site-specific PSCO phenomenon in Lu1-xScxFeO3, in which octahedrally coordinated Fe3+ in orthorhombic LuFeO3 and trigonal-bipyramidally coordinated Fe3+ in hexagonal Lu0.5Sc0.5FeO3 show distinct PSCO response to external pressure. X-ray emission spectra and DFT calculations reveal the key role of coordination environment in a PSCO process and predict the occurrence of PSCO for trigonal-bipyramidally coordinated Fe3+ above 100 GPa, far beyond that of 50 GPa for octahedrally coordinated Fe3+ in LuFeO3. The demonstration of site-specific PSCO sheds light on the state-of-the-art design of PSCO materials for directional applications.

BaBOF3: a new aurivillius-like borate containing two types of F atoms.

Herein, a new fluorine-containing borate, BaBOF3, has been synthesized by a boric acid flux method. It possesses two types of F atoms, which are involved in the pseudo-Aurivillius type [Ba2F2]2+ layers and the unique infinite [BOF2]- chains. The first-principles calculations on the title compound were performed to elucidate the structure-property relationship.

K11RbB28O48: a new triple-layered borate with an unprecedented [B28O57] fundamental building block.

A new mixed-alkali borate, K11RbB28O48, has been obtained using the high-temperature solution method. It features a new [B28O57] fundamental building block. Meanwhile, these units further polymerize to form unusual triple-layered anionic groups. Thermal analysis, optical property measurement, and theoretical calculations were performed.