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.

Superconductivity in the High-Entropy Ceramics Ti0.2 Zr0.2 Nb0.2 Mo0.2 Ta0.2 Cx with Possible Nontrivial Band Topology.

Topological superconductors have drawn significant interest from the scientific community due to the accompanying Majorana fermions. Here, the discovery of electronic structure and superconductivity (SC) in high-entropy ceramics Ti0.2 Zr0.2 Nb0.2 Mo0.2 Ta0.2 Cx (x = 1 and 0.8) combined with experiments and first-principles calculations is reported. The Ti0.2 Zr0.2 Nb0.2 Mo0.2 Ta0.2 Cx high-entropy ceramics show bulk type-II SC with Tc ≈ 4.00 K (x = 1) and 2.65 K (x = 0.8), respectively. The specific heat jump (∆C/γTc ) is equal to 1.45 (x = 1) and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS superconductor in the weak coupling limit. The high-pressure resistance measurements show a robust SC against high physical pressure in Ti0.2 Zr0.2 Nb0.2 Mo0.2 Ta0.2 C, with a slight Tc variation of 0.3 K within 82.5 GPa. Furthermore, the first-principles calculations indicate that the Dirac-like point exists in the electronic band structures of Ti0.2 Zr0.2 Nb0.2 Mo0.2 Ta0.2 C, which is potentially a topological superconductor. The Dirac-like point is mainly contributed by the d orbitals of transition metals M and the p orbitals of C. The high-entropy ceramics provide an excellent platform for the fabrication of novel quantum devices, and the study may spark significant future physics investigations in this intriguing material.

Association of bone turnover markers and cognitive function in Chinese chronic schizophrenia patients with or without vitamin D insufficiency.

BACKGROUND: Increasing evidence shows that bone turnover markers (BTMs) and vitamin D can affect human cognitive function. However, there are few studies that have investigated the association between BTMs and cognitive function in chronic schizophrenia patients. The aim of this study was to investigate the relationship between BTMs and cognitive function in chronic schizophrenia patients with or without vitamin D insufficiency (VDI). METHODS: In all, 118 chronic schizophrenia patients were enrolled in this cross-sectional study. Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was applied to evaluate the cognitive function of the subjects. Blood analysis included bone turnover markers, vitamin D levels, and glycolipid levels. RESULTS: Relative to 72 vitamin D-sufficient (VDS) patients, 46 VDI patients had higher bone resorption markers levels and lower bone formation markers levels. Regression analysis showed that, in the total sample, CTX and language function exhibited independent positive correlation (p = 0.027, R2 change = 0.042), and in the VDS group, procollagen type I N-terminal propeptide (PINP) was independently negatively correlated with language function (p = 0.031, R2 change = 0.065), while the positive correlation between osteopontin (OPN) and delayed memory remained in the VDI group (p = 0.036, R2 change = 0.083). CONCLUSION: Our study showed an association between the levels of BTMs and cognitive function among chronic schizophrenia patients. This correlation may have different mechanisms of action at different vitamin D levels.

BrMYB108 confers resistance to Verticillium wilt by activating ROS generation in Brassica rapa.

Increasing plant resistance to Verticillium wilt (VW), which causes massive losses of Brassica rapa crops, is a challenge worldwide. However, few causal genes for VW resistance have been identified by forward genetic approaches, resulting in limited application in breeding. We combine a genome-wide association study in a natural population and quantitative trait locus mapping in an F2 population and identify that the MYB transcription factor BrMYB108 regulates plant resistance to VW. A 179 bp insertion in the BrMYB108 promoter alters its expression pattern during Verticillium longisporum (VL) infection. High BrMYB108 expression leads to high VL resistance, which is confirmed by disease resistance tests using BrMYB108 overexpression and loss-of-function mutants. Furthermore, we verify that BrMYB108 confers VL resistance by regulating reactive oxygen species (ROS) generation through binding to the promoters of respiratory burst oxidase genes (Rboh). A loss-of-function mutant of AtRbohF in Arabidopsis shows significant susceptibility to VL. Thus, BrMYB108 and its target ROS genes could be used as targets for genetic engineering for VL resistance of B. rapa.

The breakdown of both strange metal and superconducting states at a pressure-induced quantum critical point in iron-pnictide superconductors.

Here we report the first observation of the concurrent breakdown of the strange metal (SM) normal state and superconductivity at a pressure-induced quantum critical point in Ca10(Pt4As8)((Fe0.97Pt0.03)2As2)5 superconductor. We find that, upon suppressing the superconducting state, the power exponent (α) changes from 1 to 2, and the slope of the temperature-linear resistivity per FeAs layer (A□) gradually diminishes. At a critical pressure, A□ and superconducting transition temperature (Tc) go to zero concurrently, where a quantum phase transition from a superconducting state with a SM normal state to a non-superconducting Fermi liquid state occurs. Scaling analysis reveals that the change of A□ with Tc obeys the relation of Tc ~ (A□)0.5, similar to what is seen in other chemically doped unconventional superconductors. These results suggest that there is a simple but powerful organizational principle of connecting the SM normal state with the high-Tc superconductivity.

Clinical Characteristics, Treatment Patterns, and Effectiveness in Chinese Patients with Angina Pectoris Using Electronic Patient-Reported Outcomes: Protocol for a Multicenter, Prospective, Cohort Study (GREAT).

BACKGROUND: Angina pectoris (AP) is the initial and the most common manifestation of coronary artery disease (CAD). Therefore, management and control of AP can help prevent further complications associated with CAD. However, there is under-reporting of angina symptoms in clinical practice, resulting in under-treatment and reduced quality of life (QoL). Prospective and standardized monitoring is needed to support timely and appropriate treatment. OBJECTIVES: To establish a large cohort of Chinese patients with AP and compare the effectiveness of different anti-angina regimens with the help of electronic patient-reported outcomes (e-PROs), using the Seattle Angina Questionnaire (SAQ) to assess health status. METHODS: The registry study (GREAT) is a multicenter, prospective, observational, cohort study. Patients diagnosed with AP will be enrolled from 10 hospitals and assessed based on the different anti-anginal regimens. Patients will be followed up every 3 months from baseline to 12 months to observe the difference in the therapeutic effectiveness of the drugs. Data will be collected in the form of e-PROs combined with on-site visit records. PLANNED OUTCOMES: The change in SAQ summary score (SAQ SS) at Month 12 from baseline will be the primary outcome. The secondary measures will include changes in SAQ SS at Months 3, 6, and 9 from baseline, changes in retest results of vascular stenosis imaging at Month 12 from baseline, and medication adherence based on the proportion of days covered. Safety data will be evaluated based on the incidence of adverse events (AEs). CONCLUSION: This study will evaluate the effectiveness of anti-anginal regimens using ePROs in real-world settings in China. The results from this study may provide a new perspective on treatment patterns and the effectiveness of different anti-anginal regimens for patients with AP. STUDY REGISTRATION NUMBER: NCT05050773.

The Adaxial/Abaxial Patterning of Auxin and Auxin Gene in Leaf Veins Functions in Leafy Head Formation of Chinese Cabbage.

Leaf curling is an essential prerequisite for the formation of leafy heads in Chinese cabbage. However, the part or tissue that determines leaf curvature remains largely unclear. In this study, we first introduced the auxin-responsive marker DR5::GUS into the Chinese cabbage genome and visualized its expression during the farming season. We demonstrated that auxin response is adaxially/abaxially distributed in leaf veins. Together with the fact that leaf veins occupy considerable proportions of the Chinese cabbage leaf, we propose that leaf veins play a crucial supporting role as a framework for heading. Then, by combining analyses of QTL mapping and a time-course transcriptome from heading Chinese cabbage and non-heading pak choi during the farming season, we identified the auxin-related gene BrPIN5 as a strong candidate for leafy head formation. PIN5 displays an adaxial/abaxial expression pattern in leaf veins, similar to that of DR5::GUS, revealing an involvement of BrPIN5 in leafy head development. The association of BrPIN5 function with heading was further confirmed by its haplo-specificity to heading individuals in both a natural population and two segregating populations. We thus conclude that the adaxial/abaxial patterning of auxin and auxin genes in leaf veins functions in the formation of the leafy head in Chinese cabbage.

Quantum Phases of SrCu_{2}(BO_{3})_{2} from High-Pressure Thermodynamics.

We report heat capacity measurements of SrCu_{2}(BO_{3})_{2} under high pressure along with simulations of relevant quantum spin models and map out the (P,T) phase diagram of the material. We find a first-order quantum phase transition between the low-pressure quantum dimer paramagnet and a phase with signatures of a plaquette-singlet state below T=2 K. At higher pressures, we observe a transition into a previously unknown antiferromagnetic state below 4 K. Our findings can be explained within the two-dimensional Shastry-Sutherland quantum spin model supplemented by weak interlayer couplings. The possibility to tune SrCu_{2}(BO_{3})_{2} between the plaquette-singlet and antiferromagnetic states opens opportunities for experimental tests of quantum field theories and lattice models involving fractionalized excitations, emergent symmetries, and gauge fluctuations.

Record-High Superconductivity in Niobium-Titanium Alloy.

The extraordinary superconductivity has been observed in a pressurized commercial niobium-titanium alloy. Its zero-resistance superconductivity persists from ambient pressure to the pressure as high as 261.7 GPa, a record-high pressure up to which a known superconducting state can continuously survive. Remarkably, at such an ultra-high pressure, although the ambient pressure volume is shrunk by 45% without structural phase transition, the superconducting transition temperature (TC ) increases to ≈19.1 K from ≈9.6 K, and the critical magnetic field (HC2 ) at 1.8 K has been enhanced to 19 T from 15.4 T. These results set new records for both the TC and the HC2 among all the known alloy superconductors composed of only transition metal elements. The remarkable high-pressure superconducting properties observed in the niobium-titanium alloy not only expand the knowledge on this important commercial superconductor but also are helpful for a better understanding on the superconducting mechanism.

Robust zero resistance in a superconducting high-entropy alloy at pressures up to 190 GPa.

We report the observation of extraordinarily robust zero-resistance superconductivity in the pressurized (TaNb)0.67(HfZrTi)0.33 high-entropy alloy--a material with a body-centered-cubic crystal structure made from five randomly distributed transition-metal elements. The transition to superconductivity (TC ) increases from an initial temperature of 7.7 K at ambient pressure to 10 K at ∼60 GPa, and then slowly decreases to 9 K by 190.6 GPa, a pressure that falls within that of the outer core of the earth. We infer that the continuous existence of the zero-resistance superconductivity from 1 atm up to such a high pressure requires a special combination of electronic and mechanical characteristics. This high-entropy alloy superconductor thus may have a bright future for applications under extreme conditions, and also poses a challenge for understanding the underlying quantum physics.

Puzzle maker in SmB6: accompany-type valence fluctuation state.

In recent years, studying the Kondo insulator SmB6, a strongly correlated electron material that has been puzzling the community for decades, has again become an attractive topic due to the discovery of its unusual metallic surface state coexisting with the bulk insulating state. Many efforts have been made to understand the microphysics in SmB6, but some puzzles that have been hotly debated and argued have not been solved. In this article, based on the latest progress made in our high-pressure studies on SmB6 and the accumulating results reported by other groups, we propose a notion named the 'accompany-type valence fluctuation state', which possibly coexists with the bulk Kondo insulating ground state of SmB6. We expect that this notion could be taken as a common starting point for understanding in a unified way most of the low-temperature phenomena observed by different experimental investigations on SmB6, thus promoting the deciphering of the puzzles. We also expect that this notion could attract rigorous theoretical interpretation and further experimental investigation, or stimulate better thinking on the physics in SmB6.

Observation of a bi-critical point between antiferromagnetic and superconducting phases in pressurized single crystal Ca0.73La0.27FeAs2.

One of the most strikingly universal features of the high-temperature superconductors is that the superconducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these two phases poses a long-standing challenge. It is commonly believed that, as the antiferromagnetic transition temperature is continuously suppressed to zero, there appears a quantum critical point, around which the existence of antiferromagnetic fluctuation is responsible for the development of the superconductivity. In contrast to this scenario, we report the observation of a bi-critical point identified at 2.88GPa and 26.02K in the pressurized high-quality single crystal Ca0.73La0.27FeAs2 by complementary in-situ high pressure measurements. At the critical pressure, we find that the antiferromagnetism suddenly disappears and superconductivity simultaneously emerges at almost the same temperature, and that the external magnetic field suppresses the superconducting transition temperature but hardly affects the antiferromagnetic transition temperature.

Quantum phase transition and destruction of Kondo effect in pressurized SmB6.

SmB6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB6 under pressure provides an opportunity to acquire the much-needed understanding about the effect of electron correlations on both the metallic surface state and bulk insulating state. Here we do so by studying the evolution of two transport gaps (low temperature gap El and high temperature gap Eh) associated with the Kondo effect by measuring the electrical resistivity under high pressure and low temperature (0.3 K) conditions. We associate the gaps with the bulk Kondo hybridization, and from their evolution with pressure we demonstrate an insulator-to-metal transition at ∼4 GPa. At the transition pressure, a large change in the Hall number and a divergence tendency of the electron-electron scattering coefficient provide evidence for a destruction of the Kondo entanglement in the ground state. Our results raise the new prospect for studying topological electronic states in quantum critical materials settings.

Correlation between superconductivity and bond angle of CrAs chain in non-centrosymmetric compounds A2Cr3As3 (A = K, Rb).

Non-centrosymmetric superconductors, whose crystal structure is absent of inversion symmetry, have recently received special attentions due to the expectation of unconventional pairings and exotic physics associated with such pairings. The newly discovered superconductors A2Cr3As3 (A = K, Rb), featured by the quasi-one dimensional structure with conducting CrAs chains, belongs to such kind of superconductor. In this study, we are the first to report the finding that superconductivity of A2Cr3As3 (A = K, Rb) has a positive correlation with the extent of non-centrosymmetry. Our in-situ high pressure ac susceptibility and synchrotron x-ray diffraction measurements reveal that the larger bond angle of As-Cr-As (defined as α) in the CrAs chains can be taken as a key factor controlling superconductivity. While the smaller bond angle (defined as ß) and the distance between the CrAs chains also affect the superconductivity due to their structural connections with the α angle. We find that the larger value of α-ß, which is associated with the extent of the non-centrosymmetry of the lattice structure, is in favor of superconductivity. These results are expected to shed a new light on the underlying mechanism of the superconductivity in these Q1D superconductors and also to provide new perspective in understanding other non-centrosymmetric superconductors.

Introduction of Interfacial Charges to Black Phosphorus for a Family of Planar Devices.

The capabilities to tune the conduction properties of materials by doping or electric fields are essential for the design of electronic devices. However, in two-dimensional materials substitutional doping has been achieved in only a few systems, such as Nb substitutional doping in MoS2. Surface charge transfer is still one of the popular ways to control whether the conduction is dominated by holes or electrons. Here, we demonstrate that a capping layer of cross-linked poly(methyl methacrylate) modifies the potential in a black phosphorus (BP) layer so that conduction in the absence of an external electric field is dominated by electrons, rather than holes. Using this technique to form adjoining regions dominated by hole and electron conduction, a family of novel planar devices, such as BP-gated diodes, BP bidirectional rectifier, and BP logic inverters, can be fabricated. The devices are potentially useful for electronic applications, including rectification and switching.

Inhibition of eukaryotic initiation factor 4E phosphorylation by cercosporamide selectively suppresses angiogenesis, growth and survival of human hepatocellular carcinoma.

Mnk kinase is required for the phosphorylation and activation of the eukaryotic initiation factor 4E (eIF4E), which regulates translation of proteins involve in important aspects of hepatocellular carcinoma (HCC). Here we investigated whether an antifungal agent, cercosporamide, which had been recently identified as a potent Mnk inhibitor, is active against HCC and angiogenesis. We showed that cercosporamide significantly inhibited growth and induced caspase-dependent apoptosis on numerous HCC cell lines, while sparing normal liver cells. In addition, cercosporamide impaired HCC angiogenesis via inhibiting HCC-endothelial cells (HCC-EC) capillary network formation, migration, proliferation and survival. Importantly, cercosporamide sensitized HCC cells to cisplatin in in vitro cell culture and in vivo HCC xenograft mouse model. Cercosporamide blocked the phosphorylation of eIF4E but not Erk or p38 in a dose- and time-dependent manner in HCC and HCC-EC cells, suggesting that suppression of eIF4E phosphorylation was the result of inhibition of Mnk but not Mnk upstream pathways. Overexpression of constitutively active eIF4E (S209D) but not the nonphosphorylatable eIF4E (S209A) abolished the inhibitory effects of cercosporamide in HepG2 cells. Altogether, our work demonstrates that cercosporamide acts as a Mnk inhibitor through blockage of eIF4E phosphorylation and selectively exhibits anti-HCC activities. Our work suggests that targeting MNK-eIF4E pathway represents a therapeutic strategy to overcome chemo-resistance for HCC treatment.

Pressure-induced exotic states in rare earth hexaborides.

Finding the exotic phenomena in strongly correlated electron systems (SCESs) and understanding the corresponding microphysics have long been the research frontiers of condensed matter physics. The remarkable examples for the intriguing phenomena discovered in past years include unconventional superconductivity, heavy Fermion behaviors, giant magneto-resistance and so on. A fascinating type of rare earth hexaboride RB6 (R = Sm, Yb, Eu and Ce) belongs to a strongly correlated electron system (SCES), but shows unusual ambient-pressure and high-pressure behaviors beyond the phenomena mentioned above. Particularly, the recent discovery of the coexistence of an unusual metallic surface state and an insulating bulk state in SmB6, known to be a Kondo insulator decades ago, by theoretical calculations and many experimental measurements creates new interest for the investigation of the RB6. This significant progress encourages people to revisit the RB6 with an attempt to establish a new physics that links the SCES and the unusual metallic surface state which is a common feature of a topological insulator (TI). It is well known that pressure has the capability of tuning the electronic structure and modifying the ground state of solids, or even inducing a quantum phase transition which is one of the kernel issues in studies of SCESs. In this brief review, we will describe the progress in high pressure studies on the RB6 based on our knowledge and research interests, mainly focusing on the pressure-induced phenomena in YbB6 and SmB6, especially on the quantum phase transitions and their connections with the valence state of the rare earth ions. Moreover, some related high-pressure results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section.

Superconductivity emerging from a suppressed large magnetoresistant state in tungsten ditelluride.

The recent discovery of large magnetoresistance in tungsten ditelluride provides a unique playground to find new phenomena and significant perspective for potential applications. The large magnetoresistance effect originates from a perfect balance of hole and electron carriers, which is sensitive to external pressure. Here we report the suppression of the large magnetoresistance and emergence of superconductivity in pressurized tungsten ditelluride via high-pressure synchrotron X-ray diffraction, electrical resistance, magnetoresistance and alternating current magnetic susceptibility measurements. Upon increasing pressure, the positive large magnetoresistance effect is gradually suppressed and turned off at a critical pressure of 10.5 GPa, where superconductivity accordingly emerges. No structural phase transition is observed under the pressure investigated. In situ high-pressure Hall coefficient measurements at low temperatures demonstrate that elevating pressure decreases the population of hole carriers but increases that of the electron ones. Significantly, at the critical pressure, a sign change of the Hall coefficient is observed.

Emergence of double-dome superconductivity in ammoniated metal-doped FeSe.

The pressure dependence of the superconducting transition temperature (Tc) and unit cell metrics of tetragonal (NH3)yCs0.4FeSe were investigated in high pressures up to 41 GPa. The Tc decreases with increasing pressure up to 13 GPa, which can be clearly correlated with the pressure dependence of c (or FeSe layer spacing). The Tc vs. c plot is compared with those of various (NH3)yMxFeSe (M: metal atoms) materials exhibiting different Tc and c, showing that the Tc is universally related to c. This behaviour means that a decrease in two-dimensionality lowers the Tc. No superconductivity was observed down to 4.3 K in (NH3)yCs0.4FeSe at 11 and 13 GPa. Surprisingly, superconductivity re-appeared rapidly above 13 GPa, with the Tc reaching 49 K at 21 GPa. The appearance of a new superconducting phase is not accompanied by a structural transition, as evidenced by pressure-dependent XRD. Furthermore, Tc slowly decreased with increasing pressure above 21 GPa, and at 41 GPa superconductivity disappeared entirely at temperatures above 4.9 K. The observation of a double-dome superconducting phase may provide a hint for pursuing the superconducting coupling-mechanism of ammoniated/non-ammoniated metal-doped FeSe.

Robust antiferromagnetism preventing superconductivity in pressurized (Ba 0.61 K 0.39)Mn2Bi2.

BaMn2Bi2 possesses an iso-structure of iron pnictide superconductors and similar antiferromagnetic (AFM) ground state to that of cuprates, therefore, it receives much more attention on its properties and is expected to be the parent compound of a new family of superconductors. When doped with potassium (K), BaMn2Bi2 undergoes a transition from an AFM insulator to an AFM metal. Consequently, it is of great interest to suppress the AFM order in the K-doped BaMn2Bi2 with the aim of exploring the potential superconductivity. Here, we report that external pressure up to 35.6 GPa cannot suppress the AFM order in the K-doped BaMn2Bi2 to develop superconductivity in the temperature range of 300 K-1.5 K, but induces a tetragonal (T) to an orthorhombic (OR) phase transition at ~20 GPa. Theoretical calculations for the T and OR phases, on basis of our high-pressure XRD data, indicate that the AFM order is robust in the pressurized Ba0.61K0.39Mn2Bi2. Both of our experimental and theoretical results suggest that the robust AFM order essentially prevents the emergence of superconductivity.