查看更多>>摘要：Quasi-one-dimensional(1D)graphene nanoribbons(GNRs)play a crucial role in advancement of next-generation devices.Recent studies have suggested their potential to exhibit unique symmetry-protected topolog-ical phases defined by a Z2 invariant.By employing both the tight-binding model and the Floquet theory,our investigation demonstrates the effective control of the topological phase within quasi-1D armchair GNRs(AG-NRs)using elliptically polarized light,unveiling rich topological phase diagrams.Specifically,we observe that varying the amplitude of the light can induce transitions in the band gap(Eg)of AGNRs,leading to multiple changes in the system's Z2 invariant.Furthermore,for heterojunctions composed of different AGNR segments,the junction state can be either created or eliminated by the application of elliptically polarized light.
查看更多>>摘要：The chiral 2×2 charge order has been reported and confirmed in the kagome superconductor RbV3Sb5,while its interplay with superconductivity remains elusive owing to its lowest superconducting transition temperature Tc of about 0.85 K in the AV3Sb5 family(A=K,Rb,Cs)that severely challenges electronic spectroscopic probes.Here,utilizing dilution-refrigerator-based scanning tunneling microscopy down to 30 mK,we observe chiral 2 × 2 pair density waves with residual Fermi arcs in RbV3Sb5.We find a superconducting gap of 150 μeV with substantial residual in-gap states.The spatial distribution of this gap exhibits chiral 2×2 modulations,signaling a chiral pair density wave(PDW).Our quasi-particle interference imaging of the zero-energy residual states further reveals arc-like patterns.We discuss the relation of the gap modulations with the residual Fermi arcs under the space-momentum correspondence between PDW and Bogoliubov Fermi states.
查看更多>>摘要：La2NiO4 has a similar structure to La2CuO4 and was proposed as a high-temperature superconductor based on magnetic-moment measurements decades ago.Nevertheless,with the exception for electrical resistance drop behavior of about 4 orders of magnitude that is claimed to originate from the superconductivity ever observed in Sr-doped La2NiO4,most electrical data reported to date in La2NiO4 system exhibit a trivial insulating ground state.Here,we definitively identify the similar electrical resistance drop behavior of more than 3 orders of magnitude in La2NiO4+δ.However,our extensive investigations reveal that this phenomenon is a novel insulator-to-metal transition,distinct from superconductivity.Intriguingly,compared to the weak magnetic-field effects,pressure can significantly suppress the transition and transform from the metallic to an insulating ground state,accompanied by an isostructural phase transition.Our work not only elucidates the fundamental properties of the metallic conducting ground state in La2NiO4+δ,but also critically challenges the notion of superconductivity in single-layer lanthanum nickelates.
查看更多>>摘要：The locally noncentrosymmetric heavy fermion superconductor CeRh2As2 has attracted considerable inter-ests due to its rich superconducting phases,accompanied by possible quadrupole density wave and pronounced antiferromagnetic excitations.To understand the underlying physics,here we report measurements from high-resolution angle-resolved photoemission.Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure,as well as a quasi-two-dimensional Fermi surface(FS)with strong 4f contributions.The FS shows signs of nesting with an in-plane vector q1=(π/a,π/a),which is facilitated by the heavy bands near(X)arising from the characteristic conduction-f hybridization.The FS nesting provides a natural explanation for the observed antiferromagnetic spin fluctuations at(π/a,π/a),which might be the driving force for its unconventional superconductivity.Our experimental results can be reasonably explained by density functional theory plus dynamical mean field theory calculations,which can capture the strong correlation effects.Our study not only provides spectroscopic signature of the key factors underlying the field-induced super-conducting transition,but also uncovers the critical role of FS nesting and lattice Kondo effect in the underlying magnetic fluctuations.
查看更多>>摘要：Manipulating magnetic domain structure plays a key role in advanced spintronics devices.Theoretical ra-tionale is that the labyrinthine domain structure,normally appearing in ferromagnetic thin films with strong magnetic anisotropy,shows a great potential to increase data storage density for designing magnetic nonvolatile memory and logic devices.However,an electrical control of labyrinthine domain structure remains elusive.Here,we demonstrate the gate-driven evolution of labyrinthine domain structures in an itinerant ferromagnet Cr7Te8.By combining electric transport measurements and micromagnetic finite difference simulations,we find that the hysteresis loop of anomalous Hall effect in Cr7Te8 samples shows distinct features corresponding to the generation of labyrinthine domain structures.The labyrinthine domain structures are found to be electrically tunable via Li-electrolyte gating,and such gate-driven evolution in Cr7Te8 originates from the reduction of the magnetic anisotropic energy with gating,revealed by our micromagnetic simulations.Our results on the gate control of anomalous Hall effect in an itinerant magnetic material provide an opportunity to understand the formation and evolution of labyrinthine domain structures,paving a new route towards electric-field driven spintronics.
查看更多>>摘要：By using muon spin relaxation(μSR)measurements,we perform a comparative study of the microscopic magnetism in the parent compounds of infinite-layer nickelate superconductors RNiO2(R=La,Nd).In either compound,the zero-field μSR spectra down to the lowest measured temperature reveal no long-range magnetic order.In LaNiO2,short-range spin correlations appear below T=150 K,and spins fully freeze below T～10 K.NdNiO2 exhibits a more complex spin dynamics driven by the Nd 4f and Ni 3d electron spin fluctuations.Further,it shows features suggesting the proximity to a spin-glass state occurring below T=5K.In both compounds,the spin behavior with temperature is further confirmed by longitudinal-field μSR measurements.These results provide new insight into the magnetism of the parent compounds of the superconducting nickelates,crucial to understanding the microscopic origin of their superconductivity.
查看更多>>摘要：After the discovery of the ARECh2(A=alkali or monovalent ions,RE=rare-earth,Ch=chalcogen)trian-gular lattice quantum spin liquid(QSL)family,a series of its oxide,sulfide,and selenide counterparts has been consistently reported and extensively investigated.While KErTe2 represents the initial synthesized telluride member,preserving its triangular spin lattice,it was anticipated that the substantial tellurium ions could im-part more pronounced magnetic attributes and electronic structures to this material class.This study delves into the magnetism of KErTe2 at finite temperatures through magnetization and electron spin resonance(ESR)measurements.Based on the angular momentum(J)after spin-orbit coupling(SOC)and symmetry analysis,we obtain the magnetic effective Hamiltonian to describe the magnetism of Er3+in R(3)m space group.Applying the mean-field approximation to the Hamiltonian,we can simulate the magnetization and magnetic heat capacity of KErTe2 in paramagnetic state and determine the crystalline electric field(CEF)parameters and partial exchange interactions.The relatively narrow energy gaps between the CEF ground state and excited states exert a sig-nificant influence on the magnetism.For example,small CEF excitations can result in a significant broadening of the ESR linewidth at 2 K.For the fitted exchange interactions,although the values are small,given a large angular momentum J=15/2 after SOC,they still have a noticeable effect at finite temperatures.Notably,the heat capacity data under different magnetic fields along the c axis direction also roughly match our calculated results,further validating the reliability of our analytical approach.These derived parameters serve as crucial tools for future investigations into the ground state magnetism of KErTe2.The findings presented herein lay a foundation for exploration of the intricate magnetism within the triangular-lattice delafossite family.
查看更多>>摘要：With the increasing demand for high-resolution x-ray tomography in battery characterization,the challenges of storing,transmitting,and analyzing substantial imaging data necessitate more efficient solutions.Traditional data compression methods struggle to balance reduction ratio and image quality,often failing to preserve critical details for accurate analysis.This study proposes a machine learning-assisted compression method tailored for battery x-ray imaging data.Leveraging physics-informed representation learning,our approach significantly reduces file sizes without sacrificing meaningful information.We validate the method on typical battery materials and different x-ray imaging techniques,demonstrating its effectiveness in preserving structural and chemical details.Experimental results show an up-to-95 compression ratio while maintaining high fidelity in the projection and reconstructed images.The proposed framework provides a promising solution for managing large-scale battery x-ray imaging datasets,facilitating significant advancements in battery research and development.
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