Pressure-Tuned Intrinsic Anomalous Hall Conductivity in Kagome Magnets RV_(6)Sn_(6)(R=Gd,Tb)

Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structures carrying nontrivial topological properties hinder its progresses.Here,we investigate the pressure effect on the novel topological kagome magnets GdV_(6)Sn_(6) and TbV_(6)Sn_(6) to dig out the interplay between magnetic Gd/Tb layers and nonmagnetic V-based kagome sublattice.The pressure-tuned magnetic transition temperature Tm in both the compounds exhibit a turning point at the critical pressure P_(c),accompanied with a sign reversal in anomalous Hall effect(AHE).The separation of intrinsic and extrinsic contributions using the Tian-Ye-Jin scaling model suggests that the intrinsic mechanism originating from the electronic Berry curvature holds the priority in the competition with extrinsic mechanism in AHE.The above-mentioned findings can be attributed to the combined effect of pressure-tuned band topology and magnetic interaction in segregated layers.Our results provide a practical route to design and manipulate the intrinsic AHE in magnetic topological materials.

Pressure-Induced Superconductivity in the Charge-Density-Wave Compound LaTe_(2-x)Sb_(x)(x=0 and 0.4)

Magnetic CeTe_(2)achieving superconductivity under external pressure has received considerable attention.The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism arising from magnetic fluctuations.Here,we address this speculation using a nonmagnetic 4f-electron-free LaTe_(2)as an example.No structural phase transition can be observed up to 35 GPa in the in situ synchrotron diffraction patterns.Subsequent high-pressure electrical measurements show that LaTe_(2)exhibits superconductivity at20 Gpa with its T_(c)(4.5 K)being two times higher than its Ce-counterpart.Detailed theoretical calculations reveal that charge transfer from the 4p orbitals of the planar square Te-Te network to the 5d orbitals of La is responsible for the emergence of superconductivity in LaTe_(2),as confirmed by Hall experiments.Furthermore,we study the modulation of q_(CDW)by Sb substitution and find a record high T_(c)^(onset)~6.5 K in LaTe_(1.6)Sb_(0.4).Our work provides an informative clue to comprehend the role of 5d-4p hybridization in the relationship between charge density wave(CDW)and superconductivity in these RETe_(2)(RE=rare-earth elements)compounds.

Recent progress on high-pressure and hightemperature studies of fullerenes and related materials

Polymerization of fullerenes is an interesting topic that has been studied for almost three decades.A rich polymeric phase diagram of C60 has been drawn under a variety of pressure P and temperature T conditions.Knowledge of the targeted preparation and structural control of fullerene polymers has become increasingly important because of their utility in producing novel fullerenebased architectures with unusual properties and potential applications.This paper focuses on the polymeric phases of fullerenes and their derivatives under high P and/or high T.First,the polymerization behavior and the various polymeric phases of C60 and C70 under such conditions are briefly reviewed.A summary of the polymerization process of intercalated fullerenes is then presented,and a synthetic strategy for novel structural and functional fullerene polymers is proposed.Finally,on the basis of the results of recent research,a proposal is made for further studies of endohedral fullerenes at high P.

Pressure-Induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator

Recently,natural van der Waals heterostructures of(MnBi2 Te4)m(Bi2 Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states.We systematically investigate both the structural and electronic responses of MnBi2 Te4 and MnBi4 Te7 to external pressure.In addition to the suppression of antiferromagnetic order,MnBi2 Te4 is found to undergo a metalsemiconductor-metal transition upon compression.The resistivity of MnBi4 Te7 changes dramatically under high pressure and a non-monotonic evolution of p(T)is observed.The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime.We find that the bulk and surface states respond differently to pressure,which is consistent with the non-monotonic change of the resistivity.Interestingly,a pressure-induced amorphous state is observed in MnBi2 Te4,while two high-pressure phase transitions are revealed in MnBi4 Te7.Our combined theoretical and experimental research establishes MnBi2 Te4 and MnBi4 Te7 as highly tunable magnetic topological insulators,in which phase transitions and new ground states emerge upon compression.

Quantum Oscillations in Noncentrosymmetric Weyl Semimetal SmAlSi

As a new type of quantum state of matter hosting low energy relativistic quasiparticles,Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications.In this study,we present a comprehensive investigation of the structural,magnetic,and transport properties of noncentrosymmetric RAl Si(R=Sm,Ce),which have been predicted to be new magnetic WSM candidates.Both samples exhibit nonsaturated magnetoresistance,with about 900%and 80%for Sm Al Si and Ce Al Si,respectively,at temperature of 1.8 K and magnetic field of 9 T.The carrier densities of Sm Al Si and Ce Al Si exhibit remarkable change around magnetic transition temperatures,signifying that the electronic states are sensitive to the magnetic ordering of rare-earth elements.At low temperatures,Sm Al Si reveals prominent Shubnikov–de Haas oscillations associated with the nontrivial Berry phase.High-pressure experiments demonstrate that the magnetic order is robust and survival under high pressure.Our results would yield valuable insights into WSM physics and potentials in applications to next-generation spintronic devices in the RAl Si(R=Sm,Ce)family.

Superconductivity in the Layered Cage Compound Ba_(3)Rh_(4)Ge_(16)

We report the synthesis and superconducting properties of a layered cage compound Ba_(3)Rh_(4)Ge_(16).Similar to Ba_(3)Ir_(4)Ge_(16),the compound is composed of 2 D networks of cage units,formed by noncubic Rh-Ge building blocks,in marked contrast to the reported rattling compounds.The electrical resistivity,magnetization,specific heat capacity,andμSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T_(c)=7.0 K,the upper critical field μ_(0)H_(c2)(0)~2.5 T,the electron-phonon coupling strength λ_(e-ph)~0.80,and the Ginzburg-Landau parameterκ~7.89.The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T_(c) and coupling between the cage and guest atoms.Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ_(e-ph) strength and T_(c).

Pressure-induced reemergence of superconductivity in BaIr_(2)Ge_(7)and Ba_(3)Ir_(4)Ge_(16)with cage structures

Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility,as well as their fertile physical properties.Here,we report the pressure-induced reemergence of superconductivity in BaIr2Ge7 and Ba3Ir4Ge16,two new caged superconductors with two-dimensional building blocks of cage structures.After suppression of the ambient-pressure superconducting(SC-I)states,new superconducting(SC-II)states emerge unexpectedly,with Tc increased to a maximum of 4.4 and 4.0 K for BaIr2Ge7 and Ba3Ir4Ge16,respectively.Combined with high-pressure synchrotron x-ray diffraction and Raman measurements,we propose that the reemergence of superconductivity in these caged superconductors can be ascribed to a pressure-induced phonon softening linked to cage shrinkage.

拓扑异质结(PbSe)_(5)(Bi_(2)Se_(3))_(6)高压诱导超导电性研究

最近,天然异质结(PbSe)_(5)(Bi_(2)Se_(3))_(6)在理论上预测并实验证实为拓扑绝缘体.本文通过高压原位量子调控在(PbSe)_(5)(Bi_(2)Se_(3))_(6)中成功引入超导电性.当压力增加到10 GPa时,超导电性突然出现,T_(c)约为4.6 K,随后T_(c)急剧下降.值得注意的是,当进一步施加压力到30 GPa以上时,出现了一种新的超导态,且T_(c)直到本实验最高压力仍未饱和.结合XRD和拉曼光谱,我们认为(PbSe)_(5)(Bi_(2)Se_(3))_(6)中两个超导态的出现与压力诱导的结构相变有关.拓扑异质结压力下出现新的量子态,为进一步研究拓扑和超导的关系提供了一个良好的平台.

Pressure-Induced Intermetallic Charge Transfer and Semiconductor- Metal Transition in Two-Dimensional AgRuO_(3)

The intricate correlation between charge degrees of freedom and physical properties is a fascinating area of research in solid state chemistry and condensed matter physics.Herein,we report on the pressureinduced successive charge transfer and accompanied resistive evolution in honeycomb layered ruthenate AgRuO_(3).Structural revisiting and spectroscopic analyses affirm the ilmenite type R-3 structure with mixed valence cations as Ag^(+1/+2)Ru^(+4/+5)O_(3) at ambient pressure.In-situ pressure-and temperature-dependent resistance variation reveals a successive insulatormetal-insulator transition upon pressing,accompanied by unprecedented charge transfer between Ag and Ru under applied pressure,and a further structural phase transition in the insulator region at higher pressure.These phenomena are also corroborated by in-situ pressure-dependent Raman spectra,synchrotron X-ray diffraction,bond valence sums,and electronic structure calculations,emphasizing the dominated rare Ag2+,and near zero thermal expansion in the ab-plane in the metallic zone mostly due to the Jahn-Teller effect of d9-Ag2+.The multiple electronic instabilities in AgRuO_(3) may offer new possibilities toward novel and unconventionally physical and chemical behaviors in strongly correlated honeycomb lattices.

Pressure-Tunable Large Anomalous Hall Effect in Ferromagnetic Metal LiMn_(6)Sn_(6)

Recently, giant intrinsic anomalous Hall effect(AHE) has been observed in the materials with kagome lattice.Here, we systematically investigate the influence of high pressure on the AHE in the ferromagnet LiMn_(6)Sn_(6) with clean Mn kagome lattice. Our in situ high-pressure Raman spectroscopy indicates that the crystal structure of LiMn_(6)Sn_(6) maintains a hexagonal phase under high pressures up to 8.51 GPa. The anomalous Hall conductivity(AHC) σ_(xy)^(A) remains around 150 Ω^(-1)·cm^(-1), dominated by the intrinsic mechanism. Combined with theoretical calculations, our results indicate that the stable AHE under pressure in Li Mn_(6)Sn_(6) originates from the robust electronic and magnetic structure.

Distinct superconducting behaviors of pressurized WB2 and ReB2 with different local B layers

The recent discovery of superconductivity up to 32 K in the pressurized MoBreignites the interest in exploring high-Tc superconductors in transition-metal diborides. Inspired by that work, we turn our attention to the 5 d transition-metal diborides.Here we systematically investigate the responses of both structural and physical properties of WBand ReBto external pressure,which possess different types of boron layers. Similar to MoB, the pressure-induced superconductivity was also observed in WBabove 60 GPa with a maximum Tcof 15 K at 100 GPa, while no superconductivity was detected in ReBin this pressure range. Interestingly, the structures at ambient pressure for both WBand ReBpersist to high pressure without structural phase transitions. Theoretical calculations suggest that the ratio of flat boron layers in this class of transition-metal diborides may be crucial for the appearance of high Tc. The combined theoretical and experimental results highlight the effect of the geometry of boron layers on superconductivity and shed light on the exploration of novel high-Tcsuperconductors in borides.