Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical pr...Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).展开更多
The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and car...The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV_(3)Sb_(5),we find that the charge order becomes suppressed under a modest pressure pc(1.4 GPa<pc<1.6 GPa),while the superconducting transition temperature Tc is maximized.Tc is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa,before exhibiting another{maximum}around 22.8 GPa,signifying the presence of a second superconducting dome.Distinct normal state resistance anomalies are found to be associated with the second superconducting dome,similar to KV_(3)Sb_(5).Our findings point to qualitatively similar temperature-pressure phase diagrams in KV_(3)Sb_(5) and RbV_(3)Sb_(5),{and suggest a close link}between the second superconducting dome and the high-pressure resistance anomalies.展开更多
When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show ...When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show the nonlinearity and heating-induced frequency shifts of the Kittel mode and HMS mode in a yttrium-iron-garnet(YIG)sphere.When the Kittel mode is driven to generate a certain number of excitations,the temperature of the whole YIG sample rises and the HMS mode can display an induced frequency shift,and vice versa.This cross effect provides a new method to study the magnetization dynamics and paves a way for novel cavity magnonic devices by including the heating effect as an operational degree of freedom.展开更多
The coupling between electric ordering and magnetic ordering in two-dimensional(2D)materials is important for both fundamental research of 2D multiferroics and future development of magnetism-based information storage...The coupling between electric ordering and magnetic ordering in two-dimensional(2D)materials is important for both fundamental research of 2D multiferroics and future development of magnetism-based information storage and operation.Here,we introduce a scheme for realizing a magnetic phase transition through the transition of electric ordering.We take CuMoP_(2)S_(6) monolayer as an example,which is a member of the large 2D transition-metal chalcogen-phosphates family.Based on first-principles calculations,we find that it is a multiferroic with unprecedented characters,namely,it exhibits two different phases:an antiferroelectric-antiferromagnetic phase and a ferroelectric-ferromagnetic phase,in which the electric and magnetic orderings are strongly coupled.Importantly,the electric polarization is out-of-plane,so the magnetism can be readily switched by using the gate electric field.Our finding reveals a series of 2D multiferroics with special magnetoelectric coupling,which hold great promise for experimental realization and practical applications.展开更多
A central research topic in condensed matter physics is the understanding of the evolution of various phases and phase transitions under different tuning parameters such as temperature, magnetic field and pressure. To...A central research topic in condensed matter physics is the understanding of the evolution of various phases and phase transitions under different tuning parameters such as temperature, magnetic field and pressure. To explore the pressure-induced evolution of the magnetism and Fermi surface of the heavy fermion antiferromagnet Yb Pt Bi, we performed tunnel diode oscillator based measurements under pressure at low temperatures in high magnetic fields. Our results reveal that the magnetic order strengthens and the Fermi surface shrinks as the pressure increases, which are consistent with typical observations for Yb-based heavy fermion compounds. In addition, an anomalous change in the quantum oscillation amplitudes is observed above 1.5 GPa, and determining the origin requires further study.展开更多
The noncentrosymmetricity of a prototypical correlated electron system Ca3Ru2O7 renders extensive interest in the possible polar metallic state,along with multiple other closely competing interactions.However,the stru...The noncentrosymmetricity of a prototypical correlated electron system Ca3Ru2O7 renders extensive interest in the possible polar metallic state,along with multiple other closely competing interactions.However,the structural domain formation in this material often complicates the study of intrinsic material properties.It is crucial to fully characterize the structural domains for unrevealing underlying physics.Here,we report the domain imaging on Ca3Ru2O7 crystal using the reflection of polarized light at normal incidence.The reflection anisotropy measurement utilizes the relative orientation between electric field component of the incident polarized light and the principal axis of the crystal,and gives rise to a peculiar contrast.The domain walls are found to be the interfaces between 90° rotated twin crystals by complementary magnetization measurements.A distinct contrast in reflectance is also found in the opposite cleavage surfaces,owing to the polar mode of the RuO6 octahedra.More importantly,the analysis of the contrast between all inequivalent cleavage surfaces enables a direct determination of the crystallographic orientation of each domain.Such an approach provides an efficient yet feasible method for structural domain characterization,which can also find applications in noncentrosymmetric crystals in general.展开更多
The group-V monolayers(MLs)have been studied intensively after the experimental fabrication of two-dimensional(2D)graphene and black phosphorus.The observation of novel quantum phenomena,such as quantum spin Hall effe...The group-V monolayers(MLs)have been studied intensively after the experimental fabrication of two-dimensional(2D)graphene and black phosphorus.The observation of novel quantum phenomena,such as quantum spin Hall effect and ferroelectricity in group-V elemental layers,has attracted tremendous attention because of the novel physics and promising applications for nanoelectronics in the 2D limit.In this review,we comprehensively review recent research progress in engineering of topology and ferroelectricity,and several effective methods to control the quantum phase transition are discussed.We then introduce the coupling between topological orders and ferroelectric orders.The research directions and outlooks are discussed at the end of the perspective.It is expected that the comprehensive overview of topology and ferroelectricity in 2D group-V materials can provide guidelines for researchers in the area and inspire further explorations of interplay between multiple quantum phenomena in low-dimensional systems.展开更多
We report the successful synthesis of a new diluted magnetic semiconductor(Ca,Na)(Zn,Mn)2Sb2.Na and Mn are doped into the parent compound CaZn2Sb2,which has the same crystal structure as that of"122"type iro...We report the successful synthesis of a new diluted magnetic semiconductor(Ca,Na)(Zn,Mn)2Sb2.Na and Mn are doped into the parent compound CaZn2Sb2,which has the same crystal structure as that of"122"type iron-based superconductor CaFe2As2.Na substitution for Ca and Mn substitution for Zn introduce carriers and spins,respectively.Doping Mn atoms alone up to 5%does not induce any type of magnetic ordering.When both Na and Mn are co-doped,a ferromagnetic ordering with maximum TC^10 K has been observed.Iso-thermal magnetization shows that the coercive field is up to^245 Oe at 2 K.Below TC,a negative magneto-resistance with MR^12%has also been achieved.展开更多
A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are the...A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are then obtained in an unified way.The essential characteristics such as the possible first-order phase transition can be detected analytically.This approach can be easily applied to the recent experiments with various tunable parameters without much additional effort,so it should be very helpful to the analysis of the experimental data.展开更多
In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed...In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.展开更多
Non-Abelian anyons are exotic quasiparticle excitations hosted by certain topological phases of matter.They break the fermion-boson dichotomy and obey non-Abelian braiding statistics:their interchanges yield unitary o...Non-Abelian anyons are exotic quasiparticle excitations hosted by certain topological phases of matter.They break the fermion-boson dichotomy and obey non-Abelian braiding statistics:their interchanges yield unitary operations,rather than merely a phase factor,in a space spanned by topologically degenerate wavefunctions.They are the building blocks of topological quantum computing.However,experimental observation of non-Abelian anyons and their characterizing braiding statistics is notoriously challenging and has remained elusive hitherto,in spite of various theoretical proposals.Here,we report an experimental quantum digital simulation of projective non-Abelian anyons and their braiding statistics with up to 68 programmable superconducting qubits arranged on a two-dimensional lattice.By implementing the ground states of the toric-code model with twists through quantum circuits,we demonstrate that twists exchange electric and magnetic charges and behave as a particular type of non-Abelian anyons,i.e.,the Ising anyons.In particular,we show experimentally that these twists follow the fusion rules and non-Abelian braiding statistics of the Ising type,and can be explored to encode topological logical qubits.Furthermore,we demonstrate how to implement both single-and two-qubit logic gates through applying a sequence of elementary Pauli gates on the underlying physical qubits.Our results demonstrate a versatile quantum digital approach for simulating non-Abelian anyons,offering a new lens into the study of such peculiar quasiparticles.展开更多
We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In ...We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In our proposal,we use a dissipative TLS ensemble and an active cavity with effective gain.In the weak drive-field limit,the QPT can occur under the combined actions of the loss and gain of the system.Owing to the active cavity,the QPT behavior can be much differentiated even for a finite strength of the drive field on the TLS ensemble.Also,we propose to implement our scheme based on the dissipative nitrogen-vacancy(NV)centers coupled to an active optical cavity made from the gainmedium-doped silica.Furthermore,we show that the QPT can be measured by probing the transmission spectrum of the cavity embedding the ensemble of the NV centers.展开更多
As a representative of small aromatic molecules, triphenylene(TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP...As a representative of small aromatic molecules, triphenylene(TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP molecules on Ru(0001) by using scanning tunneling microscopy(STM). In submonolayer regime, TP molecules are randomly dispersed on Ru(0001) and the TP overlayer can be thoroughly dehydrogenated and converted into graphene islands at 700 K. Due to weak interaction between TP molecules and graphene, the grooves formed among graphene islands have confinement effect on TP molecules. TP adopts a flat-lying adsorption mode and has two adsorption configurations with the 3-fold molecular axis aligned almost parallel or antiparallel to the ■ direction of the substrate. At TP coverages of 0.6 monolayer(ML)and 0.8 ML, the orientational distributions of the two adsorption configurations are equal. At about 1.0 ML, we find the coexistence of locally ordered and disordered phases. The ordered phase includes two sets of different superstructures with the symmetries of ■R23.41° and p(4 × 4), respectively. The adsorption behavior of TP on Ru(0001) can be attributed to the delicate balance between molecule–substrate and molecule–molecule interactions.展开更多
Realization of a flexible and tunable coupling scheme among qubits is critical for scalable quantum information processing.Here,we design and characterize a tunable coupling element based on Josephson junction,which c...Realization of a flexible and tunable coupling scheme among qubits is critical for scalable quantum information processing.Here,we design and characterize a tunable coupling element based on Josephson junction,which can be adapted to an all-to-all connected circuit architecture where multiple Xmon qubits couple to a common coplanar waveguide resonator.The coupling strength is experimentally verified to be adjustable from 0 MHz to about 40 MHz,and the qubit lifetime can still be up to 12μs in the presence of the coupling element.展开更多
Investigations on adsorption behavior of triphenylene(TP) and subsequent graphene self-assembly on Cu(111) were carried out mainly by using scanning tunneling microscopy(STM).At monolayer coverage,TP molecules formed ...Investigations on adsorption behavior of triphenylene(TP) and subsequent graphene self-assembly on Cu(111) were carried out mainly by using scanning tunneling microscopy(STM).At monolayer coverage,TP molecules formed a longrange ordered adsorption structure on Cu(111) with an uniform orientation.Graphene self-assembly on the Cu(111) substrate with TP molecules as precursor was achieved by annealing the sample,and a large-scale graphene overlayer was successfully captured after the sample annealing up to 1000 K.Three different Moire patterns generated from relative rotational disorders between the graphene overlayer and the Cu(111) substrate were observed,one with 40 rotation between the graphene overlayer and the Cu(111) substrate with a periodicity of 2.93 nm,another with 70 rotation and 2.15 nm of the size of the Moire supercell,and the third with 100 rotation with a periodicity of 1.35 nm.展开更多
We propose a controllable exponential-Cosine Gaussian vortex(ECGV)beam,which can evolve into the different beam profiles with three parameters:distance modulation factor(DMF),split modulation factor(SMF)and rotation m...We propose a controllable exponential-Cosine Gaussian vortex(ECGV)beam,which can evolve into the different beam profiles with three parameters:distance modulation factor(DMF),split modulation factor(SMF)and rotation modulation factor(RMF).When SMF is 0,the ECGV beam appears as a perfect single-ring vortex beam and the ring radius can be adjusted by the DMF.We deduce from mathematics and give the reason for the single-ring characteristics.When SMF is not 0,the beam splits symmetrically.DMF,SMF and RMF control the number,distance and rotation angle of the split,respectively.Our experiments verify the correctness of the theory.展开更多
We have carried out point-contact spectroscopy(PCS)measurements on one family of antiferromagnetic Kondo semiconductor CeT2Al10(T=Ru and Os)with a Neel temperature´TN∼27.5 and 28.5 K,respectively.Their PCS condu...We have carried out point-contact spectroscopy(PCS)measurements on one family of antiferromagnetic Kondo semiconductor CeT2Al10(T=Ru and Os)with a Neel temperature´TN∼27.5 and 28.5 K,respectively.Their PCS conductance curves both exhibit a characteristic coherent double-peak-structure at temperatures below TN,signaling an AFM gap around the Fermi surface.The temperature dependent AFM gap∆1 follows a Bardeen-Cooper-Schrieffer(BCS)-like mean-field behavior with a moderate gap anisotropy for PCS along different crystal axes.Another asymmetric gap-like feature is observed for both compounds at temperatures far below TN,which is consistent with opening of a new hybridization gap∆h inside the long-range ordered AFM state.Our results suggest a common itinerant nature of the anomalous AFM ordering,constraining theoretical models to explain the AFM origin in CeRu2Al10 and CeOs2Al10.展开更多
We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured ex...We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured exactly.Two kinds of PT symmetry broken phases are found,whose effective Hamiltonians differ by a constant ω/2.For the time-periodic dissipation,a vanishingly small dissipation strength can lead to the PT symmetry breaking in the (2k-1)-photon resonance(△=(2k-1)ω),with k=1,2,3…It is worth noting that such a phenomenon can also happen in 2k-photon resonance(△=2kω),as long as the dissipation strengths or the driving times are imbalanced,namely γo≠-γ1orT0≠T1.For the time-periodic coupling,the weak dissipation induced$\mathcal{PT}$symmetry breaking occurs at △eff=kω,where △eff=(△0T0+△1 T1)/T.In the high frequency limit,the phase boundary is given by a simple relation γeff=±△eff.展开更多
We report the successful fabrication of a new 1111-type bulk magnetic semiconductor(La,Ba)(Zn,Mn)SbO through the solid solution of(La,Ba)and(Zn,Mn)in the parent compound LaZnSbO.The polycrystalline samples(La,Ba)(Zn,M...We report the successful fabrication of a new 1111-type bulk magnetic semiconductor(La,Ba)(Zn,Mn)SbO through the solid solution of(La,Ba)and(Zn,Mn)in the parent compound LaZnSbO.The polycrystalline samples(La,Ba)(Zn,Mn)SbO crystallize into ZrCuSiAs-type tetragonal structure,which has the same structure as iron-based superconductor LaFeAsO_(1-δ).The DC magnetization measurements indicate the existence of spin-glass ordering,and the coercive field is up to~11500 Oe(1 Oe=79.5775 A·m^(-1)).The AC magnetic susceptibility further determines that the samples evolve into a conventional spin-glass ordering state below the spin freezing temperature T_(f).In addition,the negative magnetoresistance(MR≡[ρ(H)-ρ(0)]/ρ(0))reaches-88%under 9 T.展开更多
Complex oxide heterointerfaces can host a rich of emergent phenomena,and epitaxial growth is usually at the heart of forming these interfaces.Recently,a strong crystalline-orientation-dependent two-dimensional superco...Complex oxide heterointerfaces can host a rich of emergent phenomena,and epitaxial growth is usually at the heart of forming these interfaces.Recently,a strong crystalline-orientation-dependent two-dimensional superconductivity was discovered at interfaces between KTaO_(3)single-crystal substrates and films of other oxides.Unexpectedly,rare of these oxide films was epitaxially grown.Here,we report the existence of superconductivity in epitaxially grown LaVO_(3)/KTaO_(3)(111)heterostructures,with a superconducting transition temperature of~0.5 K.Meanwhile,no superconductivity was detected in the(001)-and(110)-orientated LaVO_(3)/KTaO_(3)heterostructures down to 50 mK.Moreover,we find that for the LaVO_(3)/KTaO_(3)(111)interfaces to be conducting,an oxygen-deficient growth environment and a minimum LaVO_(3)thickness of~0.8 nm(~2 unit cells)are needed.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFE0202700 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.11974422 and 12104504)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)Fundamental Research Funds for the Central Universities,and Research Funds of Renmin University,China(Grant No.22XNKJ30)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2023 of Renmin University,China。
文摘Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).
基金the National Key R&D Program of China(Grant Nos.2017YFA0303100 and 2016YFA0300202)the Key R&D Program of Zhejiang Province,China(Grant No.2021C01002)+3 种基金the National Natural Science Foundation of China(Grant Nos.11974306 and 12034017)the Fundamental Research Funds for the Central Universities of Chinasupport via the UC Santa Barbara NSF Quantum Foundry funded via the Q-AMASE-i program under award DMR-1906325support from the California Nano Systems Institute through the Elings fellowship program。
文摘The kagome metals AV_(3)Sb_(5)(A=K,Rb,Cs)under ambient pressure exhibit an unusual charge order,from which superconductivity emerges.In this work,by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV_(3)Sb_(5),we find that the charge order becomes suppressed under a modest pressure pc(1.4 GPa<pc<1.6 GPa),while the superconducting transition temperature Tc is maximized.Tc is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa,before exhibiting another{maximum}around 22.8 GPa,signifying the presence of a second superconducting dome.Distinct normal state resistance anomalies are found to be associated with the second superconducting dome,similar to KV_(3)Sb_(5).Our findings point to qualitatively similar temperature-pressure phase diagrams in KV_(3)Sb_(5) and RbV_(3)Sb_(5),{and suggest a close link}between the second superconducting dome and the high-pressure resistance anomalies.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11934010,U1801661,and 12174329)the Zhejiang Province Program for Science and Technology(Grant No.2020C01019)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2021FZZX001-02)the China Postdoctoral Science Foundation(Grant No.2019M660137)
文摘When there is a certain amount of field inhomogeneity,the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic(HMS)mode in addition to the uniform-precession Kittel mode.In cavity magnonics,we show the nonlinearity and heating-induced frequency shifts of the Kittel mode and HMS mode in a yttrium-iron-garnet(YIG)sphere.When the Kittel mode is driven to generate a certain number of excitations,the temperature of the whole YIG sample rises and the HMS mode can display an induced frequency shift,and vice versa.This cross effect provides a new method to study the magnetization dynamics and paves a way for novel cavity magnonic devices by including the heating effect as an operational degree of freedom.
基金Supported by the National Key R&D Program of China(Grant No.2019YFE0112000)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR21A040001)the National Natural Science Foundation of China(Grant No.11974307,12088101,11991060,and U1930402).
文摘The coupling between electric ordering and magnetic ordering in two-dimensional(2D)materials is important for both fundamental research of 2D multiferroics and future development of magnetism-based information storage and operation.Here,we introduce a scheme for realizing a magnetic phase transition through the transition of electric ordering.We take CuMoP_(2)S_(6) monolayer as an example,which is a member of the large 2D transition-metal chalcogen-phosphates family.Based on first-principles calculations,we find that it is a multiferroic with unprecedented characters,namely,it exhibits two different phases:an antiferroelectric-antiferromagnetic phase and a ferroelectric-ferromagnetic phase,in which the electric and magnetic orderings are strongly coupled.Importantly,the electric polarization is out-of-plane,so the magnetism can be readily switched by using the gate electric field.Our finding reveals a series of 2D multiferroics with special magnetoelectric coupling,which hold great promise for experimental realization and practical applications.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.11974306 and 12034017)the Natural Science Foundation of Zhejiang Province(Grant No.2021C01002)。
文摘A central research topic in condensed matter physics is the understanding of the evolution of various phases and phase transitions under different tuning parameters such as temperature, magnetic field and pressure. To explore the pressure-induced evolution of the magnetism and Fermi surface of the heavy fermion antiferromagnet Yb Pt Bi, we performed tunnel diode oscillator based measurements under pressure at low temperatures in high magnetic fields. Our results reveal that the magnetic order strengthens and the Fermi surface shrinks as the pressure increases, which are consistent with typical observations for Yb-based heavy fermion compounds. In addition, an anomalous change in the quantum oscillation amplitudes is observed above 1.5 GPa, and determining the origin requires further study.
基金Supported by the National Key Research and Development Program of China(Grant Nos.2019YFA0308602 and 2016YFA0300500)the National Natural Science Foundation of China(Grant Nos.11804220,11774305 and 11974237)Natural Science Foundation of Shanghai(Grant No.20ZR1428900).
文摘The noncentrosymmetricity of a prototypical correlated electron system Ca3Ru2O7 renders extensive interest in the possible polar metallic state,along with multiple other closely competing interactions.However,the structural domain formation in this material often complicates the study of intrinsic material properties.It is crucial to fully characterize the structural domains for unrevealing underlying physics.Here,we report the domain imaging on Ca3Ru2O7 crystal using the reflection of polarized light at normal incidence.The reflection anisotropy measurement utilizes the relative orientation between electric field component of the incident polarized light and the principal axis of the crystal,and gives rise to a peculiar contrast.The domain walls are found to be the interfaces between 90° rotated twin crystals by complementary magnetization measurements.A distinct contrast in reflectance is also found in the opposite cleavage surfaces,owing to the polar mode of the RuO6 octahedra.More importantly,the analysis of the contrast between all inequivalent cleavage surfaces enables a direct determination of the crystallographic orientation of each domain.Such an approach provides an efficient yet feasible method for structural domain characterization,which can also find applications in noncentrosymmetric crystals in general.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974307 and 61574123)Zhejiang Provincial Natural Science Foundation,China(Grant No.D19A040001)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe 2DMOST,Shenzhen University(Grant No.2018028).
文摘The group-V monolayers(MLs)have been studied intensively after the experimental fabrication of two-dimensional(2D)graphene and black phosphorus.The observation of novel quantum phenomena,such as quantum spin Hall effect and ferroelectricity in group-V elemental layers,has attracted tremendous attention because of the novel physics and promising applications for nanoelectronics in the 2D limit.In this review,we comprehensively review recent research progress in engineering of topology and ferroelectricity,and several effective methods to control the quantum phase transition are discussed.We then introduce the coupling between topological orders and ferroelectric orders.The research directions and outlooks are discussed at the end of the perspective.It is expected that the comprehensive overview of topology and ferroelectricity in 2D group-V materials can provide guidelines for researchers in the area and inspire further explorations of interplay between multiple quantum phenomena in low-dimensional systems.
基金Project supported by the National Key Research&Development Program of China(Grant No.2016YFA0300402)the Fundamental Research Funds for the Central Universities,China。
文摘We report the successful synthesis of a new diluted magnetic semiconductor(Ca,Na)(Zn,Mn)2Sb2.Na and Mn are doped into the parent compound CaZn2Sb2,which has the same crystal structure as that of"122"type iron-based superconductor CaFe2As2.Na substitution for Ca and Mn substitution for Zn introduce carriers and spins,respectively.Doping Mn atoms alone up to 5%does not induce any type of magnetic ordering.When both Na and Mn are co-doped,a ferromagnetic ordering with maximum TC^10 K has been observed.Iso-thermal magnetization shows that the coercive field is up to^245 Oe at 2 K.Below TC,a negative magneto-resistance with MR^12%has also been achieved.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11834005 and 11674285).
文摘A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are then obtained in an unified way.The essential characteristics such as the possible first-order phase transition can be detected analytically.This approach can be easily applied to the recent experiments with various tunable parameters without much additional effort,so it should be very helpful to the analysis of the experimental data.
基金Project supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grants Nos.2017YFA0303002and 2016YFA0300204)the Fundamental Research Funds for the Central Universities,China
文摘In this study, we have explored the ways to fabricate and optimize high-quality ultrathin YBa2 Cu3 O7-δ(YBCO) films grown on single-crystal(001) SrTiO3 substrates. Nearly atomic-flat YBCO films are obtained by pulsed laser deposition.Our result shows that the termination of SrTiO3 has only a negligible effect on the properties of YBCO. In contrast, we found that capping a non-superconducting oxide layer can generally enhance the superconductivity of YBCO. PrBa2 Cu3 O7,La2 CuO4, LaMnO3, SrTiO3, and LaAlO3 have been examined as capping layers, and the minimum thickness of superconducting YBCO with capping is ~ 2 unit cells–3 unit cells. This result might be useful in constructing good-performance YBCO-based field effect devices.
基金the National Natural Science Foundation of China(Grants Nos.92065204,12075128,T2225008,12174342,12274368,12274367,U20A2076,and 11725419)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300200)+2 种基金the Zhejiang Province Key Research and Development Program(Grant No.2020C01019)supported by Tsinghua Universitythe Shanghai Qi Zhi Institute。
文摘Non-Abelian anyons are exotic quasiparticle excitations hosted by certain topological phases of matter.They break the fermion-boson dichotomy and obey non-Abelian braiding statistics:their interchanges yield unitary operations,rather than merely a phase factor,in a space spanned by topologically degenerate wavefunctions.They are the building blocks of topological quantum computing.However,experimental observation of non-Abelian anyons and their characterizing braiding statistics is notoriously challenging and has remained elusive hitherto,in spite of various theoretical proposals.Here,we report an experimental quantum digital simulation of projective non-Abelian anyons and their braiding statistics with up to 68 programmable superconducting qubits arranged on a two-dimensional lattice.By implementing the ground states of the toric-code model with twists through quantum circuits,we demonstrate that twists exchange electric and magnetic charges and behave as a particular type of non-Abelian anyons,i.e.,the Ising anyons.In particular,we show experimentally that these twists follow the fusion rules and non-Abelian braiding statistics of the Ising type,and can be explored to encode topological logical qubits.Furthermore,we demonstrate how to implement both single-and two-qubit logic gates through applying a sequence of elementary Pauli gates on the underlying physical qubits.Our results demonstrate a versatile quantum digital approach for simulating non-Abelian anyons,offering a new lens into the study of such peculiar quasiparticles.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11934010,U1801661,U1930402,and 11847087)the National Key Research and Development Program of China(Grant No.2016YFA0301200)。
文摘We study the dissipative quantum phase transition(QPT)in a biased Tavis–Cummings model consisting of an ensemble of two-level systems(TLSs)interacting with a cavity mode,where the TLSs are pumped by a drive field.In our proposal,we use a dissipative TLS ensemble and an active cavity with effective gain.In the weak drive-field limit,the QPT can occur under the combined actions of the loss and gain of the system.Owing to the active cavity,the QPT behavior can be much differentiated even for a finite strength of the drive field on the TLS ensemble.Also,we propose to implement our scheme based on the dissipative nitrogen-vacancy(NV)centers coupled to an active optical cavity made from the gainmedium-doped silica.Furthermore,we show that the QPT can be measured by probing the transmission spectrum of the cavity embedding the ensemble of the NV centers.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0503100)the National Natural Science Foundation of China(Grant No.11790313)
文摘As a representative of small aromatic molecules, triphenylene(TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP molecules on Ru(0001) by using scanning tunneling microscopy(STM). In submonolayer regime, TP molecules are randomly dispersed on Ru(0001) and the TP overlayer can be thoroughly dehydrogenated and converted into graphene islands at 700 K. Due to weak interaction between TP molecules and graphene, the grooves formed among graphene islands have confinement effect on TP molecules. TP adopts a flat-lying adsorption mode and has two adsorption configurations with the 3-fold molecular axis aligned almost parallel or antiparallel to the ■ direction of the substrate. At TP coverages of 0.6 monolayer(ML)and 0.8 ML, the orientational distributions of the two adsorption configurations are equal. At about 1.0 ML, we find the coexistence of locally ordered and disordered phases. The ordered phase includes two sets of different superstructures with the symmetries of ■R23.41° and p(4 × 4), respectively. The adsorption behavior of TP on Ru(0001) can be attributed to the delicate balance between molecule–substrate and molecule–molecule interactions.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304300 and 2016YFA0300600)the National Natural Science Foundation of China(Grant Nos.11725419 and 11434008)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)
文摘Realization of a flexible and tunable coupling scheme among qubits is critical for scalable quantum information processing.Here,we design and characterize a tunable coupling element based on Josephson junction,which can be adapted to an all-to-all connected circuit architecture where multiple Xmon qubits couple to a common coplanar waveguide resonator.The coupling strength is experimentally verified to be adjustable from 0 MHz to about 40 MHz,and the qubit lifetime can still be up to 12μs in the presence of the coupling element.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0503100)the National Natural Science Foundation of China(Grant No.11790313).
文摘Investigations on adsorption behavior of triphenylene(TP) and subsequent graphene self-assembly on Cu(111) were carried out mainly by using scanning tunneling microscopy(STM).At monolayer coverage,TP molecules formed a longrange ordered adsorption structure on Cu(111) with an uniform orientation.Graphene self-assembly on the Cu(111) substrate with TP molecules as precursor was achieved by annealing the sample,and a large-scale graphene overlayer was successfully captured after the sample annealing up to 1000 K.Three different Moire patterns generated from relative rotational disorders between the graphene overlayer and the Cu(111) substrate were observed,one with 40 rotation between the graphene overlayer and the Cu(111) substrate with a periodicity of 2.93 nm,another with 70 rotation and 2.15 nm of the size of the Moire supercell,and the third with 100 rotation with a periodicity of 1.35 nm.
基金the National Natural Science Foundation of China(Grant No.11874321)。
文摘We propose a controllable exponential-Cosine Gaussian vortex(ECGV)beam,which can evolve into the different beam profiles with three parameters:distance modulation factor(DMF),split modulation factor(SMF)and rotation modulation factor(RMF).When SMF is 0,the ECGV beam appears as a perfect single-ring vortex beam and the ring radius can be adjusted by the DMF.We deduce from mathematics and give the reason for the single-ring characteristics.When SMF is not 0,the beam splits symmetrically.DMF,SMF and RMF control the number,distance and rotation angle of the split,respectively.Our experiments verify the correctness of the theory.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303101 and 2016FYA0300402)the National Natural Science Foundation of China(Grant Nos.11674279,11774404,and 11374257)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR18A04001)the Japan Society for the Promotion of Science KAKENHI(Grant Nos.JP26400363,JP16H01076,and JP17K05545).
文摘We have carried out point-contact spectroscopy(PCS)measurements on one family of antiferromagnetic Kondo semiconductor CeT2Al10(T=Ru and Os)with a Neel temperature´TN∼27.5 and 28.5 K,respectively.Their PCS conductance curves both exhibit a characteristic coherent double-peak-structure at temperatures below TN,signaling an AFM gap around the Fermi surface.The temperature dependent AFM gap∆1 follows a Bardeen-Cooper-Schrieffer(BCS)-like mean-field behavior with a moderate gap anisotropy for PCS along different crystal axes.Another asymmetric gap-like feature is observed for both compounds at temperatures far below TN,which is consistent with opening of a new hybridization gap∆h inside the long-range ordered AFM state.Our results suggest a common itinerant nature of the anomalous AFM ordering,constraining theoretical models to explain the AFM origin in CeRu2Al10 and CeOs2Al10.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11674285 and 11834005)the National Key Research and Development Program of China(Grant No.2017YFA0303002).
文摘We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured exactly.Two kinds of PT symmetry broken phases are found,whose effective Hamiltonians differ by a constant ω/2.For the time-periodic dissipation,a vanishingly small dissipation strength can lead to the PT symmetry breaking in the (2k-1)-photon resonance(△=(2k-1)ω),with k=1,2,3…It is worth noting that such a phenomenon can also happen in 2k-photon resonance(△=2kω),as long as the dissipation strengths or the driving times are imbalanced,namely γo≠-γ1orT0≠T1.For the time-periodic coupling,the weak dissipation induced$\mathcal{PT}$symmetry breaking occurs at △eff=kω,where △eff=(△0T0+△1 T1)/T.In the high frequency limit,the phase boundary is given by a simple relation γeff=±△eff.
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2022YFA1402701 and 2022YFA1403202)the National Natural Science Foundation of China (Grant No.12074333)the Key Research and Development Program of Zhejiang Province,China (Grant No.2021C01002)。
文摘We report the successful fabrication of a new 1111-type bulk magnetic semiconductor(La,Ba)(Zn,Mn)SbO through the solid solution of(La,Ba)and(Zn,Mn)in the parent compound LaZnSbO.The polycrystalline samples(La,Ba)(Zn,Mn)SbO crystallize into ZrCuSiAs-type tetragonal structure,which has the same structure as iron-based superconductor LaFeAsO_(1-δ).The DC magnetization measurements indicate the existence of spin-glass ordering,and the coercive field is up to~11500 Oe(1 Oe=79.5775 A·m^(-1)).The AC magnetic susceptibility further determines that the samples evolve into a conventional spin-glass ordering state below the spin freezing temperature T_(f).In addition,the negative magnetoresistance(MR≡[ρ(H)-ρ(0)]/ρ(0))reaches-88%under 9 T.
基金the National Natural Science Foundation of China(Grant Nos.11934016 and 12074334)the Key R&D Program of Zhejiang Province,China(Grant Nos.2020C01019 and 2021C01002)the Fundamental Research Funds for the Central Universities of China.
文摘Complex oxide heterointerfaces can host a rich of emergent phenomena,and epitaxial growth is usually at the heart of forming these interfaces.Recently,a strong crystalline-orientation-dependent two-dimensional superconductivity was discovered at interfaces between KTaO_(3)single-crystal substrates and films of other oxides.Unexpectedly,rare of these oxide films was epitaxially grown.Here,we report the existence of superconductivity in epitaxially grown LaVO_(3)/KTaO_(3)(111)heterostructures,with a superconducting transition temperature of~0.5 K.Meanwhile,no superconductivity was detected in the(001)-and(110)-orientated LaVO_(3)/KTaO_(3)heterostructures down to 50 mK.Moreover,we find that for the LaVO_(3)/KTaO_(3)(111)interfaces to be conducting,an oxygen-deficient growth environment and a minimum LaVO_(3)thickness of~0.8 nm(~2 unit cells)are needed.
